# Consensus for a postoperative atlas of sinonasal substructures from a modified Delphi study to guide radiotherapy in sinonasal malignancies

Florent Carsuzaa, Valentin Favier, Lise Seguin, Mario Turri-Zanoni,

Anna-Maria Camarda, Benjamin Verillaud, Philippe Herman, Daniele

Borsetto, Alberto Schreiber, Stefano Taboni, et al.

► To cite this version:

Florent Carsuzaa, Valentin Favier, Lise Seguin, Mario Turri-Zanoni, Anna-Maria Camarda, et al. Consensus for a postoperative atlas of sinonasal substructures from a modified Delphi study to guide radiotherapy in sinonasal malignancies. Radiotherapy & Oncology, 2025, 206, pp.110784. 10.1016/j.radonc.2025.110784. hal-04995116

HAL Id: hal-04995116

https://hal.science/hal-04995116v1

Submitted on 23 Jan 2026

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target volumes. To enhance the accuracy of poRT planning, histological and radiological correlations are necessary to locate the tumor attachment on poRT CT scans. An accurate atlas of structures resected or identified during EESBS could serve for the interdisciplinary postoperative management of patients, personalizing poRT by adequate radiation dose delivery. The objective of this study was to achieve a consensual segmentation atlas on CT scan with surgeons practicing EESBS and radiation oncologists.

**Methods:** The sinonasal structures relevant for poRT of sinonasal malignancies were determined by a two-round Delphi process. A rating group of 25 European experts in sinonasal malignancies was set up. Consensual structures emerged and were used to determine the anatomical limits of the retained structures to draft an atlas with expert based relevant structures. The atlas was then critically reviewed, discussed, and edited by another 2 skull base surgeons and 2 radiation oncologists.

**Results:** After the two rating rounds, 46 structures obtained a strong agreement, 7 an agreement, 5 were rejected and 5 did not reach consensus. The atlas integrating all the selected structures is presented attached.

**Conclusion:** Consensual segmentation atlas on CT scan might allow, through careful poRT planning to limit the morbidity of poRT while maintaining good local control. Prospective studies are necessary to validate this potential precision medicine-based approach.

## Introduction

Sinonasal and skull base tumor surgery-related morbidity in sinonasal malignancies has been reduced in the past decades with the evolution of endoscopic endonasal skull base surgical (EESBS) procedures, with equivalent oncological outcomes to open approaches [1-6]. Postoperative radiation therapy (poRT), often necessary as an adjuvant modality with or without concomitant chemotherapy, has dramatically evolved in the last two decades with the implementation of simultaneous integrated boost RT through intensity-modulated RT (IMRT), volumetric modulated arc therapy (VMAT), and proton RT (PT) [7,8]. Although sharp dose profiles usually achieved with these techniques, with special reference to PT, allow for better tumor dose conformity, they are also more susceptible to topographical misses. This susceptibility is amplified when considering the elevated anatomical uncertainties, especially with PT. Thus, the precise definition and delineation of target tumor volumes are crucial in modern RT.

EESBS operative report can be used to provide a detailed and accurate mapping of the sinonasal and skull base tumor involvement. The precise identification of tumor location is also a key factor to understand the anatomical tumor involvement, and the quality of surgical resection margins, especially in the era of EESBS due to no monobloc resection. Orbital preservation best represents the compromise made to achieve acceptable oncological results while maximizing functional outcomes [9].

Sinonasal tumors are often pedicled, with a large intraluminal compartment bulging into the cavities and pushing or destroying surrounding structures. EESBS allows to visualize the pedicle tumor site and its extension, which can be precisely reported on standardized anatomic 3D drawings and as detailed reports [10]. Such surgeon's feedback / reports after EESBS are necessary for radiation oncologists to better locate the tumor implantation. Preoperative imaging alone may overestimate tumor involvement due to compression or inflammation caused by the bulging part of the tumor [11]. Moreover, the professionals of a multidisciplinary tumor board meeting have a different vision of anatomical structures which depends on the practical interests or constraints linked to the prism of their discipline. EESBS operative reports can also be used to accurately identify tumor involvement of anatomical structures. Finally, a better interdisciplinary communication [12] may help to personalize poRT in sinonasal malignancies by facilitating dose-painting radiotherapy, in a customized and interdisciplinary approach.

We hypothesized that standardization of operative and pathological reports could assist radiation oncologists in achieving this goal, by improving the delineation of tumor margins and dissemination pathways on postoperative CT scans. To further enhance the precision of poRT planning, accurate histo-radiological correlation is relevant to locate each fragment on successive planar images from the radiotherapy planning scanner. The determination of volumes to be irradiated is typically based on pre-operative imaging, operative and pathological

reports, and knowledge of anatomical extensions [13]. An accurate radio-anatomical segmentation atlas (i.e., anatomical region of interest delineated on a CT scan) of structures resected or identified during EESBS could serve for the interdisciplinary postoperative management of patients with sinonasal tumors, but none exists in the current literature.

The objective of this study was to achieve a consensual segmentation atlas on CT scan, using a modified Delphi method applied to a committee of EESBS surgeons and radiation oncologists.

## Methods

### Definition of sinonasal structures

The sinonasal structures relevant for poRT in sinonasal malignancies were determined by a two-round Delphi process [14]. The Delphi methodology is an iterative process used to achieve consensus from different opinions on open questions that are not sufficiently supported by evidence (Fig. 1). A steering committee (SC) of 5 experts (2 radiation oncologists: JT, EO; and 3 EESBS surgeons: FC, VF, MF) was tasked with identifying relevant sinonasal structures. The initial list of structures was established from an anatomical diagram for sinonasal malignant tumor resection reporting published by Bastier et al. (n = 24) [10], to which relevant contiguous structures were added.

<figure><img src="image_2.png" /><figcaption>Fig. 1. Overview of the two rounds Delphi process.</figcaption></figure>
## Definition of consensus and outliers' management

In the first round, the experts had to rate the statements between 1 and 9 (1: totally disagree; 9: totally agree), as recommended in the guidelines of the French Health Authority [15] (Table 1). For a cohort comprising over 16 experts, the initial round of analysis allows for the omission of either two missing values or two values that diverge from the majority of the group. Strong positive and negative agreements emerged. For other items without consensus, the SC provided an anonomized summary of the experts' opinions from the first round as well as the reasons they provided their judgments. The panel had to revise their early replies considering the replies of the other experts. After this second round, strong agreements and agreements emerged (Table 1). Similarly to the first round, the analysis in the second round allows for the omission of two missing values or two values that are contrary to the majority of the group.

## Creation of the sinonasal subunit atlas

After having determined the anatomical limits of the retained structures, a draft atlas was first generated by 2 skull base surgeons (FC, LS), 1 radiation oncologist (JT), and 1 neuroradiologist (PYM). Delination of sinonasal structures was performed on CT scans from healthy patients (whose CT scans were considered normal, acquired with a slice thickness of 1 mm or less) with the help of 3D MR sequences (acquired with a 2 mm slice thickness or isotropic voxel size) using RayStation® V12 (RaySearch Laboratories, Stockholm, Sweden). The atlas was then critically reviewed, discussed, and edited by another 2 skull base surgeons (VF, MF) and 2 radiation oncologists (EO, AMC). The final atlas resulted from a consensus of all the investigators.

## Statistics

Quantitative variables are presented as medians with interquartile ranges (IQR). Comparisons between the responses of surgeons and radiation oncologists were compared using Student t-test. All statistical analyses were performed using R (version 3.3.2).

<table><caption>**Table 1**
Proposals accepted after the first and second round depending on median value and distribution of quotes.</caption><thead><tr><th colspan="5">First round</th></tr><tr><th></th><th>Proposal judged</th><th>Median value</th><th>Distribution of quotes</th><th>Subjected to the second round</th></tr></thead><tbody><tr><td rowspan="2">Appropriate</td><td>Strong consensus</td><td>≥7</td><td>All the quotes between [7-9]</td><td>No, recommendation accepted</td></tr><tr><td>Consensus</td><td>≥7</td><td>All the quotes between [5-9]</td><td>Yes</td></tr><tr><td rowspan="2">Inappropriate</td><td>Strong consensus</td><td>≤3</td><td>All the quotes between [1-3]</td><td>No, recommendation rejected</td></tr><tr><td>Consensus</td><td>≤3.5</td><td>All the quotes between [1-5]</td><td>Yes</td></tr><tr><td>Uncertain</td><td>Lack of consensus</td><td>All the other situation</td><td></td><td>No</td></tr></tbody><thead><tr><th colspan="5">Second round</th></tr><tr><th></th><th>Proposal judged</th><th>Median value</th><th>Distribution of quotes</th><th></th></tr></thead><tbody><tr><td rowspan="2">Appropriate</td><td>Strong consensus</td><td>≥7</td><td>All the quotes between [7-9] except 2 missing or &lt; 7</td><td></td></tr><tr><td>Consensus</td><td>≥7</td><td>All the quotes between [5-9] except 2 missing or &lt; 7</td><td></td></tr><tr><td rowspan="2">Inappropriate</td><td>Strong consensus</td><td>≤3</td><td>All the quotes between [1-3] except 2 missing or &gt; 3</td><td></td></tr><tr><td>Consensus</td><td>≤3.5</td><td>All the quotes between [1-5] except 2 missing or &gt; 5</td><td></td></tr></tbody></table>

## Results

A group of 25 international experts in sinonasal malignancies was assembled, consisting of 15 otolaryngology and skull base surgeons and 10 radiation oncologists. They all complete the two rounds of the Delphi study.

Fifty-nine items were proposed to the rating group during the first round. At the end of the first round, 39 were accepted with strong agreement, 1 was rejected with strong agreement and 19 were proposed in the second round. During the second round, 4 new items were proposed by the panelists and were accepted with strong agreement. At the end of the two rating rounds, 46 items obtained a strong agreement, 7 an agreement, 4 were rejected and 5 did not reach consensus. The result of the two rating rounds and the details of the structures retained in the atlas are described in Table 3.

Some differences in rating between surgeons and radiation oncologists emerged. Surgeons considered the medial orbital gyrus more important than radiation oncologists (median: 6 vs 3.4; p = 0.0074). Surgeons tended to consider the vertebrae C1-C2 (p = 0.78), Eustachian tube (p = 0.78), optic canal (p = 0.27), pterygoid canal, lower (p = 0.07) and middle (p = 0.06) clivus, gyrus rectus (p = 0.57), crista galli (p = 0.26), olfactory cleft (p = 0.18), cribriform plate (p = 0.07), and frontal process of maxilla (p = 0.77) more important to include in the atlas than radiation oncologists. Radiation oncologists tended to consider superior turbinate and nasopharyngeal walls more important than surgeons (p = 0.07 and p = 0.32, respectively). The limits of the anatomical structures retained are defined in Table 2.

The atlas integrating all the selected structures has been built and is presented in overall view in Figs. 2 and 3 and in its entirety in Supplementary Material [16].

## Discussion

The comparatively lower morbidity rate associated with EESBS, relative to traditional open approaches, can be effectively combined with modern radiation modalities to offer individual therapeutic options with reduced complications while maintaining high efficacy [17,18]. In poRT planning for sinonasal malignancies, the virtual transfer of sinonasal tumor location from preoperative views to postoperative axial CT is crucial during the delineation phase. This process is pivotal not only to the accurate delineation of the macroscopic disease but also for selecting target volumes at risk of harboring microscopic disease, informed by histopathological data.

EESBS represents a significant shift for radiation oncologists, necessitating thorough documentation and understanding of tumor extents and quality of surgical margins to ensure effective tumor control. EESBS resection results in the piecemeal resection into smaller tissue fragments, often measuring only a few millimeters. Surgeons typically annotate and orient each of these fragments [10]. It is key to standardize the orientation of surgical sampling and the resection of anatomical areas. Operative reports, whether graphical or textual, serve as the foundation for a universal language among all specialties involved in managing patients with sinonasal tumors. These reports enable pathologists to identify safe tissue fragments, tumor sub-volumes, and assess the quality of tumor margins and additional surgical margins. Their analysis is crucial for evaluating margin quality and informing the radiation oncologists about the prescribed dose [19]. Post-operative imaging relies on radiotherapy CT. Additional imaging, such as MRI, is not standard practice; it might become more systematic in the future to address postoperative changes and it may be recommended in case of gross disease. The use of segmentation atlases of the sinonasal subunits would make it possible to better harmonize the reporting of areas resected during surgery and those at risk and make it possible to consider dose-painting poRT adapted to patients and their tumors' characteristics. The consensus guidelines developed by Grégoire et al. and Brouwer et al. underscore the importance of standardizing target
<table><caption>**Table 2**
Anatomic definition of retained structures.</caption><thead><tr><th>Segmentation</th><th>Pair or single</th><th>Radiological definition</th></tr></thead><tbody><tr><td>Nasal bone</td><td>Pair</td><td>Bone located the more anteriorly in the face, in connection with the frontal, ethmoid perpendicular plate, and maxilla bones</td></tr><tr><td>Nasal septum</td><td>Single</td><td>Composed of perpendicular plate of septal cartilage, ethmoid perpendicular plate, premaxilla-maxillary crest and vomer bone.</td></tr><tr><td>Nasal floor</td><td>Pair</td><td>Lower boundary of the nasal fossa, which constitute the medial part of the hard palate. It is composed by the horizontal process of the maxillary bone anteriorly and the horizontal process of the palatine bone posteriorly. Anterior limit: anterior nasal spine; Posterior limit: posterior border of the palatine bone horizontal process</td></tr><tr><td>Inferior turbinate</td><td>Pair</td><td>Composed of a separate bone covered by mucosa that articulates with the inferior margin of the maxillary hiatus. It is also connected with the uncinate process upward, the vertical process of the maxillary bone anteriorly the vertical lamella of the palatine bone posteriorly.</td></tr><tr><td>Middle turbinate</td><td>Pair</td><td>Composed by the head, the body and the tail of the middle turbinate. Medially and superiorly has a vertical attachment to the skull base at the lateral border of the cribriform plate. The vertical attachment is in a paramedian sagittal plane. At mid road, this attachment rotates 90° to follow transversely the ethmoid roof and to reach the lamina papyracea close to the orbit. This is the basal lamella of the middle turbinate which separates the ethmoid labyrinth in anterior and posterior group relative to the basal lamella.</td></tr><tr><td>Medial maxillary wall</td><td>Pair</td><td>Bone component of the medial maxillary sinus wall</td></tr><tr><td>Anterior maxillary wall</td><td>Pair</td><td>Bone component of the anterior maxillary sinus wall excluding the sinus floor and roof</td></tr><tr><td>Posterolateral maxillary wall and sinus floor</td><td>Pair</td><td>Bone component of the posterior, lateral, and inferior wall of the sinus (with dental roots)</td></tr><tr><td>Medial orbital wall</td><td>Pair</td><td>Bone component of the medial wall of the orbit. Composed by the lacrymal bone anteriorly and the lamina papyracea posteriorly: smooth, oblong bone plate which forms the lateral surface of the labyrinth of the ethmoid bone. The frontal bone allows the junction between the medial orbital wall and the roof.</td></tr><tr><td>Orbital roof</td><td>Pair</td><td>Bone component of the superior wall of the orbit. In case of lateral pneumatization of the frontal sinus, the orbital roof form the floor of the frontal sinus anteriorly. Posteriorly, the orbital roof is the lateral part of the anterior cranial fossa</td></tr><tr><td>Orbital floor</td><td>Pair</td><td>The inferior wall of the orbit. Formed by the orbital surface of the maxilla, the orbital surface of the zygomatic bone, the orbital process of the palatine bone. The floor is separated from the posterior wall by the inferior orbital fissure, which connects the orbit to pterygopalatine and infra-temporal fossa.</td></tr><tr><td>Medial rectus muscle</td><td>Pair</td><td>Oculomotor muscle located laterally to the medial orbital wall</td></tr><tr><td>Frontal process of the maxilla</td><td>Pair</td><td>Part of the maxillary bone forming the anterior part of the nasal fossa and frontal</td></tr></tbody></table>

<table><caption>**Table 2 (continued)**</caption><thead><tr><th>Segmentation</th><th>Pair or single</th><th>Radiological definition</th></tr></thead><tbody><tr><td>Lacrimal sac and nasolacrimal duct</td><td>Pair</td><td>sinus. It articulates with nasal bones anteriorly, with the ethmoid and frontal bones anteriorly, with the lacrymal bone posteriorly<br/>The lacrimal sac receives the common canaliculus of the lacrimal drainage system, formed from the union of the superior and inferior canaliculi. The sac lies within the lacrimal fossa of the medial orbital wall. The nasolacrimal duct leaves the inferior aspect of the lacrimal sac, runs inferiorly and enters the inferior meatus approximately 10–15 mm from the head of the inferior turbinate. The nasolacrimal tract includes the bone (unguis and vertical process of the maxillary bone)</td></tr><tr><td>Internal canthus</td><td>Pair</td><td>Skin in front of the lacrimal sac</td></tr><tr><td>Infraorbital foramen</td><td>Pair</td><td>Foramen located in the anterior wall of maxillary sinus, forming the anterior end of the infraorbital canal which transmits the infraorbital nerve and vessels.</td></tr><tr><td>Anterior ethmoid</td><td>Pair</td><td>Cells located anteriorly to the basal lamella to the vertical process of the maxillary bone</td></tr><tr><td>Posterior ethmoid</td><td>Pair</td><td>Cells located posteriorly to the basal lamella and anteriorly to the anterior wall of the sphenoid (not including the bony part of the sphenoid)</td></tr><tr><td>Ethmoid roof</td><td>Pair</td><td>In coronal view, between the orbital plate of the frontal bone, and the vertical lateral lamella laterally and the cribriform plate medially</td></tr><tr><td>Cribriform plate</td><td>Pair</td><td>Bordered anteriorly by the inferior aspect of the frontal bones, posteriorly by the sphenoid planum, medially by the nasal septum and laterally by the superior and middle turbinates.</td></tr><tr><td>Olfactory cleft</td><td>Pair</td><td>Air space located between the middle and superior turbinate laterally, the nasal septum medially, the cribriform plate and the sphenoid planum superiorly, the anterior wall of the sphenoid sinus posteriorly. The inferior border of this space is virtual and projects at the level of the lower edge of the middle turbinate</td></tr><tr><td>Olfactory fossa</td><td>Pair</td><td>Medial part of the anterior cranial fossa located above the cribriform plate, where the olfactory bulb take place. The two olfactory fossae are separated by the crista galli anteriorly.</td></tr><tr><td>Superior turbinate</td><td>Pair</td><td>Composed by the head, the body and the tail of the superior turbinate. Superiorly has a vertical attachment to the skull base at the lateral border of the cribriform plate, posterior to the middle turbinate insertion. The vertical attachment is in a paramedian sagittal plane. The basal lamella is an attachment to the nasal lateral wall.</td></tr><tr><td>Frontal sinus anterior wall</td><td>Pair</td><td>Bone component of the anterior frontal sinus wall.</td></tr><tr><td>Frontal sinus posterior wall</td><td>Pair</td><td>Bone component of the frontal sinus posterior wall, which constitute the anterior wall of the anterior cranial fossa.</td></tr><tr><td>Crista galli</td><td>Single</td><td>Intracranial component of the ethmoid bone, located behind the foramen caecum, between the both cribriform plates and extending superiorly close to the sagittal veinous sinus. Its anterior border is posterior to the frontal sinus posterior wall.</td></tr><tr><td>Sphenoid intersinus septum</td><td>Single</td><td>Bone component of the sphenoid sinus medial walls, separating the sphenoid in two sphenoid sinuses.</td></tr></tbody></table>

(continued on next page)
<table><caption>**Table 2 (continued)**</caption><thead><tr><th>Segmentation</th><th>Pair or single</th><th>Radiological definition</th></tr></thead><tbody><tr><td>Sphenoid sinus anterior wall</td><td>Pair</td><td>Bone component of the sphenoid sinus anterior wall, between the nasal septum and the medial wall of the orbit. Its medial single extension is the <i>rostrum sphenoidale</i>, which articulates with the vertical plate of the vomer</td></tr><tr><td>Sphenoid sinus lateral wall</td><td>Pair</td><td>Bone component of the sphenoid sinus lateral wall</td></tr><tr><td>Sphenoid sinus superior wall</td><td>Pair</td><td>Bone component of the sphenoid sinus superior wall (planum sphenoidale)</td></tr><tr><td>Middle clivus</td><td>Single</td><td>Bone component of the clivus located at the posterosuperior border of the nasopharynx, below the sella turcica, from the glossopharyngeal nerve to the foramen magnum</td></tr><tr><td>Inferior clivus</td><td>Single</td><td>Inferior part of the clivus located posteriorly to the nasopharynx between the exits of the trigeminal and the glossopharyngeal nerves</td></tr><tr><td>Cavernous sinus</td><td>Pair</td><td>Venous structure located in close contact with the lateral wall of the sphenoid sinus, allowing the pathway for oculomotor nerves and internal carotid artery. Cavernous sinuses are on either side of the sella turcica and pituitary gland</td></tr><tr><td>Meckel's cave</td><td>Pair</td><td>Posterolateral to the cavernous sinus on either side of the sphenoid bone. Medial to the ganglion in Meckel's cave is the internal carotid artery in the posterior portion of the cavernous sinus. Inferior is the motor root of the trigeminal nerve and the petrous apex of the petrous temporal bone with the internal carotid artery traversing the carotid canal.</td></tr><tr><td>Foramen rotundum</td><td>Pair</td><td>Located in the middle cranial fossa, inferomedial to the superior orbital fissure at the base of greater wing of the sphenoid bone. Its medial border is formed by lateral wall of sphenoid sinus. It runs downwards and laterally in an oblique path and joins the middle cranial fossa with the pterygopalatine fossa.</td></tr><tr><td>Foramen ovale</td><td>Pair</td><td>An oval shaped opening in the middle cranial fossa located at the posterior base of the greater wings of the sphenoid bone, lateral to the lingula, posterolateral to the foramen rotundum.</td></tr><tr><td>Carotid canal</td><td>Pair</td><td>Passage within the petrous temporal bone that transmits the internal carotid artery. Its inferior opening is called the carotid foramen and is situated anteriorly to the jugular fossa and medially to the carotid plate. The carotid canal is initially directed superiorly, then turns anteromedially to reach up to the petrous apex. It runs approximately 2 cm within the petrous bone and opens into the middle cranial fossa superior to the foramen lacerum.</td></tr><tr><td>Pterygoid (Vidian) canal</td><td>Pair</td><td>Located in the pterygoid process of the sphenoid bone, superior to the pterygoid plates, and inferomedial to the foramen rotundum. Its position relative to the sphenoid sinus is dependent on the pneumatisation of the sinus so that the nerve may be encased in the basisphenoid bone, partially protruding into the sinus floor or occasionally exposed within the sinus cavity and connected to the floor by a bony stalk.</td></tr><tr><td>Superior orbital fissure</td><td>Pair</td><td>This fissure is of a triangular shape, and leads from the cavity of the cranium into that of the orbit. It is bounded:</td></tr></tbody></table>

<table><caption>**Table 2 (continued)**</caption><thead><tr><th>Segmentation</th><th>Pair or single</th><th>Radiological definition</th></tr></thead><tbody><tr><td>Inferior orbital fissure</td><td>Pair</td><td>• medially by the body of sphenoid;<br>• above, by the lesser wing of sphenoid;<br>• below, by the medial margin of the orbital surface of the great wing;<br>• and is completed laterally by the frontal bone</td></tr><tr><td>Optic canal</td><td>Pair</td><td>In the floor of the orbit, inferior to the superior orbital fissure and bounded superiorly by the greater wing of sphenoid, inferiorly by the maxilla and the orbital process of palatine bone and laterally by the zygomatic bone. It opens into the posterolateral aspect of orbital floor.</td></tr><tr><td>Infratemporal fossa (or deep masticator space)</td><td>Pair</td><td>Cylindrical canal running obliquely through the area where the lesser wing of sphenoid bone joins the body of sphenoid. Between the ramus of the mandible laterally and the superior constrictor muscles of the pharynx and the lateral pterygoid plate medially</td></tr><tr><td>Pterygopalatine fossa</td><td>Pair</td><td>Its anterior boundary is the posterior wall of the maxilla, and posteriorly is the base of the pterygoid process and the greater wing of the sphenoid bone. Its roof is the body of the sphenoid bone with the orbital process of the palatine bone, and the floor comprises the pyramidal process of the palatine bone with the lateral pterygoid plate</td></tr><tr><td>Lesser wings of the sphenoid</td><td>Pair</td><td>Part of the sphenoid bone located between the planum sphenoidale and the greater wing of the sphenoid. It is the superior boundary of the superior orbital fissure. It can be partially pneumatized.</td></tr><tr><td>Greater wing of the sphenoid</td><td>Pair</td><td>Sphenoid bone lateral to sphenoid body and superior to pterygoid process. It can be partially pneumatized.</td></tr><tr><td>Pterygoid plates</td><td>Pair</td><td>Bone component of the pterygoid process separated in medial and lateral plates. The medial plate of the pterygoid forms the lateral part of the choana</td></tr><tr><td>Base of the pterygoid process</td><td>Pair</td><td>Upper part of the pterygoid process at the junction of the sphenoid bone body and greater wing. Ends with the separation of pterygoid plates. It surrounds the pterygoid canal and foramen rotundum.</td></tr><tr><td>Posterior wall of the nasopharynx</td><td>Single</td><td>Mucosal, muscular, and fascial component of the posterior wall of the nasopharynx, located anteriorly to the clivus and C1-C2</td></tr><tr><td>Lateral wall of the nasopharynx</td><td>Pair</td><td>Mucosal, muscular, fascial, and cartilaginous component the lateral wall of the nasopharynx. It comprises the cartilaginous Eustachian tube</td></tr><tr><td>Roof of the nasopharynx</td><td>Single</td><td>Mucosal component of the superior wall of the nasopharynx, located inferiorly to the sphenoid body</td></tr><tr><td>Gyrus rectus (brain)</td><td>Pair</td><td>Most medial and inferior part of the frontal lobe. It is bounded medially by the interhemispheric fissure, and is separated laterally by the inferior rostral sulcus</td></tr></tbody></table>

volume delineation in head and neck oncology to minimize treatment variability and improve clinical outcomes [20,21]. However, they didn't include the sinonasal region in the atlas description, leading to a remaining gap to standardize PORT delineation in this area. Their work provides a foundation for systematic radiotherapy planning, emphasizing anatomical precision, particularly in regions of complex anatomical variability such as the sinonasal and skull base areas. This aligns closely with the objectives of our atlas, which seeks to bridge surgical observations and radiotherapeutic needs. Furthermore, the integration of histopathological insights into radiotherapy planning, as
<table><caption>**Table 3**
Results of the two rounds of Delphi process.</caption><thead><tr><th>Structure</th><th>1st round Med [IQ]</th><th>2nd round Med [IQ]</th><th>Structure</th><th>1st round Med [IQ]</th><th>2nd round Med [IQ]</th></tr></thead><tbody><tr><td>Nasal bone</td><td>9 [3-9]</td><td></td><td>Anterior sphenoidal wall*</td><td>9 [6-9]</td><td></td></tr><tr><td>Nasal septum*</td><td>9 [2-9]</td><td></td><td>Lateral sphenoidal wall</td><td>9 [7-9]</td><td></td></tr><tr><td>Nasal floor*</td><td>9 [7-9]</td><td></td><td>Posterior sphenoidal wall</td><td>9 [8,9]</td><td></td></tr><tr><td>Inferior turbinate*</td><td>8 [3-9]</td><td></td><td>Middle clivus</td><td>8 [3-9]</td><td></td></tr><tr><td>Middle turbinate*</td><td>7 [1-9]</td><td>8 [2-9]</td><td>Inferior clivus</td><td>8 [3-9]</td><td></td></tr><tr><td>Medial maxillary wall*</td><td>8 [5-9]</td><td></td><td>Superior clivus</td><td>8 [3-9]</td><td>3 [1-8]</td></tr><tr><td>Anterior maxillary wall*</td><td>9 [7-9]</td><td></td><td>Cavernous sinus</td><td></td><td>9 [5-9]</td></tr><tr><td>Posterolateral maxillary wall*</td><td>9 [7-9]</td><td></td><td>Meckel's cave</td><td></td><td>9 [3-9]</td></tr><tr><td>Uncinate process*</td><td>5 [1-9]</td><td>3 [1-8]</td><td>Foramen rotundum</td><td>9 [7-9]</td><td></td></tr><tr><td>Medial orbital wall</td><td>9 [8,9]</td><td></td><td>Foramen ovale</td><td>9 [7-9]</td><td></td></tr><tr><td>Orbital roof</td><td>9 [3-9]</td><td></td><td>Carotid canal</td><td>9 [5-9]</td><td></td></tr><tr><td>Orbital floor*</td><td>9 [5-9]</td><td></td><td>Pterygoid canal (vidian canal)</td><td>9 [3-9]</td><td></td></tr><tr><td>Medial rectus muscle</td><td>8 [3-9]</td><td>8 [2-9]</td><td>Superior orbital fissure</td><td>9 [3-9]</td><td></td></tr><tr><td>Frontal process of maxilla</td><td>7 [3-9]</td><td>7 [2-9]</td><td>Inferior orbital fissure</td><td>9 [7-9]</td><td></td></tr><tr><td>Nasolacrimal sac and duct*</td><td>8 [3-9]</td><td></td><td>Optic canal</td><td>9 [1-9]</td><td></td></tr><tr><td>Internal canthus</td><td></td><td>8 [2-9]</td><td>Infratemporal fossa</td><td>9 [8,9]</td><td></td></tr><tr><td>Inferior rectus muscle*</td><td>6 [2-9]</td><td>3 [1-8]</td><td>Temporal fossa</td><td></td><td>9 [5-9]</td></tr><tr><td>Infraorbital foramen*</td><td>9 [5-9]</td><td></td><td>Pterygopalatine fossa</td><td>9 [7-9]</td><td></td></tr><tr><td>Anterior ethmoid*</td><td>9 [5-9]</td><td></td><td>Greater wing of sphenoid</td><td>8 [3-9]</td><td>6 [1-9]</td></tr><tr><td>Posterior ethmoid*</td><td>9 [5-9]</td><td></td><td>Lesser wings of sphenoid</td><td>8 [3-9]</td><td>8 [3-9]</td></tr><tr><td>Ethmoidal roof*</td><td>9 [7-9]</td><td></td><td>Pterygoid plates</td><td>9 [4-9]</td><td>8 [3-9]</td></tr><tr><td>Cribriform plate*</td><td>9 [8,9]</td><td></td><td>Base of the pterygoid process</td><td>8 [2-9]</td><td>8 [2-9]</td></tr><tr><td>Olfactory cleft*</td><td>9 [5-9]</td><td></td><td>Vertebrae C1-C2</td><td>7 [1-9]</td><td>5 [2-9]</td></tr><tr><td>Olfactory fossa*</td><td>8 [1-9]</td><td>8 [3-9]</td><td>Posterior wall of the rhinopharynx</td><td>8 [3-9]</td><td></td></tr><tr><td>Superior turbinate*</td><td>7 [4-9]</td><td>7 [2-9]</td><td>Lateral wall of the rhinopharynx</td><td>8 [3-9]</td><td></td></tr><tr><td>Frontal recess*</td><td>8 [2-9]</td><td>6 [2-9]</td><td>Rosenmuller fossa</td><td>3 [1-8]</td><td></td></tr><tr><td>Anterior wall frontal sinus</td><td>9 [7-9]</td><td></td><td>Roof of the rhinopharynx</td><td>8 [3-9]</td><td></td></tr><tr><td>Posterior wall frontal sinus</td><td>9 [7-9]</td><td></td><td>Medial ostium of the Eustachian tube*</td><td>7 [1-9]</td><td>4 [1-9]</td></tr><tr><td>Inferior wall frontal sinus*</td><td>9 [7-9]</td><td></td><td>Eustachian tube</td><td>8 [1-9]</td><td>5 [2-8]</td></tr><tr><td>Crista galli*</td><td>8 [3-9]</td><td>8 [3-9]</td><td>Gyrus rectus (brain)</td><td>8 [3-9]</td><td>8 [2-9]</td></tr><tr><td>Sphenoid intersinus septum</td><td>9 [7-9]</td><td></td><td>Medial orbital gyrus (brain)</td><td>8 [1-9]</td><td>6 [1-9]</td></tr><tr><td>Superior sphenoidal wall</td><td>9 [7-9]</td><td></td><td></td><td></td><td></td></tr></tbody></table>

strong agreement; agreement; no consensus; strong disagreement.

outlined by these guidelines, supports the validation of our approach to creating a more personalized and effective postoperative treatment framework [20,21].

The presented consensus study identified 53 structures for which experts recommended delineation from the framework of sinonasal and skull base malignancies. These structures were identified according to endoscopic landmarks, easily identifiable anatomical regions on imaging, known tumor extension pattern and their relevance for poRT purpose. There were some differences between surgeons and radiation oncologists. Surgeons favored anatomical structures considered as essential landmarks for the surgical excision of skull base tumors. These landmarks included the C1 and C2 vertebrae and the lower and middle clivus which are often the limits of posterior excision of the tumors. However, the C1-C2 vertebrae were not consensual after adding the opinions of radiation oncologists. Probably, this is linked to the fact that these structures are easily recognizable in images from poRT CT simulation. The Eustachian tube was considered more relevant among surgeons because it represents the lateral limit of excision when the nasopharyngeal walls are involved, as well as a potential dissemination way towards the lateral skull base [22]. Another reason may be that Eustachian tube resection or irradiation is often the source of otitis media with effusion [23]. The relevance of the anatomical structure of the nasopharynx for the radiation oncologist may be linked to a greater familiarity with this structure, as it is the site of the primary tumor of the nasopharynx. Additionally, the anatomical complexity [24,25] associated with the presence of nerves, whose irradiation can lead to severe late toxicity, further emphasizes its significance [26-28]. The intracranial structures (medial orbital gyrus, gyrus rectus, crista galli), which are easily identifiable structures that can be removed according to tumor extension, were more frequently retained by surgeons. The opinions of radiation oncologists led to a lack of final consensus concerning the medial orbital gyrus. The reason for this finding may be attributed to the radiation oncologist's infrequent involvement with this structure. Specifically, since the medial orbital gyrus is separated from the gyrus rectus by the olfactory sulcus, this anatomical part may be involved mainly for olfactory neuroblastoma and adenocarcinoma. The frontal process of maxilla was also more relevant in surgeons' opinion because it can easily be individualized and because its involvement often requires a skin sacrifice [29]. The superior turbinate was more frequently retained by radiation oncologists, and it is easily individualized on imaging. This structure did not achieve a strong consensus because it requires to be grouped with the posterior ethmoid given their dissemination pathways [30]. The atlas was designed for nasoethmoid-centered tumors, which are the most common location and are less suitable for tumors of the infratemporal fossa or chordomas. We also believe that the proposed atlas may serve as a guide for a systematic analysis and standardization of sinonasal tumors extension patterns description. This atlas could then be used for imaging, surgical and pathology reports and offers a framework for detailed communication between the multidisciplinary team with the aim to allow for more precise delivery of radiation to areas of intraoperative concern or sites of historical risk for recurrence based on tumor pathology.

However, the literature lacks prospective studies concerning the reduction in morbidity made possible by better dose painting of sinonasal tumors and therapeutic de-escalation. Ongoing trials in sinonasal tumors using modern radiotherapy modalities include the French GORTEC 2016-02 phase III SANTAL trial, and the randomized phase II "SinocaRT" trial which explores de-escalation strategies in high-dose volumes, including IMRT and PT. Results from two Italian phase II trials on poor-prognosis sinonasal cancers, encompassing diverse epithelial histological subtypes, and incorporating proton and carbon ion therapy within a multidisciplinary approach, have recently been reported. While in-depth data analysis on toxicity is ongoing, the observed survival rates were similar to those reported in other series, underscoring the necessity for additional research efforts in this rare disease [26,27].

The complexity of dose distribution in poRT for sinonasal

<footnote>*: structures proposed by Bastier et al.</footnote>
<figure><img src="image_3.png" /><figcaption>Fig. 2. Captions of the atlas centered on the ethmoid.</figcaption></figure>

malignancies, with small and geometrically complex resected tumor in endoscopic techniques and surrounding structures, requires rigorous quality assurance processes [31]. In a first step, this segmentation atlas will be made automatic (ongoing process) [32]; given the number of structures, the manual delineation task would not be feasible in the busy routine clinic. Van Dijk et al. highlight the significant advancements in automatic delineation of head and neck organs at risk through deep learning contouring techniques. Their findings demonstrate that deep learning not only improves the accuracy of delineations but also reduces interobserver variability, a critical factor in complex anatomical regions like the sinonasal and skull base areas. By combining deep learning contouring with the standardized anatomical definitions of our atlas, future implementations could further refine dose-painting strategies and reduce the burden on clinicians during the delineation process [33].

However, to date, it remains difficult to train deep learning algorithms on sinonasal CT scans, as automatic segmentation and deep learning are less robust in the case of small structures. Other automatic segmentation method using less resources may be interesting to study, particularly using deformable medical image registration methods[34]. This automatic atlas will need to be adapted to the modified patient anatomy (tumor, surgery). Such adaptation is most relevantly done in tight partnership between the surgeon and the radiation oncologist. In a second step, it will serve to address the patterns of relapse more accurately than ever done. Finally, it will be necessary to group close anatomic proximity structures for which dose modulation will not be feasible in routine practice (for example, preserving the optic canal if the inferior orbital fissure is invaded by the tumor). Following such documentation, this atlas could serve to refine and likely deescalate/
<figure><img src="image_4.png" /><figcaption>Fig. 3. Caption of the atlas centered on the maxillary sinus.</figcaption></figure>

customize the clinical target volumes and to perform dose-painting in poRT for sinonasal malignancies. This entire process relies on contin-
uous interdisciplinary communication, serving as a vital prerequisite to optimize radiotherapy. The goal is to reduce irradiation volumes while maintaining or even increasing local control, as avoiding local failure becomes imperative when tailoring treatments to minimize radiation-induced morbidity.

Advancements in in-room imaging through surgical navigation sys-
tems offer intraoperative support for surgeons, potentially leading to
improved rates of safe margins and enhanced oncologic outcomes
[35,36]. The precision of the latest generation navigation systems has
reached less than 1 mm [37]. Given the intricate proximity of critical
structures such as the optic nerves, orbits, optic chiasm, pituitary gland,
internal carotid artery, cranial nerves, and the brain to complex
anatomical structures, this tool proves instrumental in minimizing sur-
gical morbidity, in a more helpful way if bony structures are involved.
Surgical navigation enables the integration of a macroscopic view with
precise CT/MRI location, providing a better understanding of the tumor
implantation area. Looking ahead, data obtained during intraoperative
navigation could be integrated with pre- and postoperative imaging to
augment accuracy. Surgeons could use a navigated pointer to delineate

the tumor implantation area during surgery, and this delineation could
be automatically transferred to postoperative imaging. This integration
facilitates the radiation oncologist's understanding of volumes at risk,
streamlining the communication of critical information between surgi-
cal and radiotherapeutic approaches and allow better dose-painting of
the tumor.

The main limitation of this study is that a modified Delphi method is
by essence an expert opinion consensus. This study design is required
when no data exists in the literature regarding the research question.
Despite the scarcity of solid evidence, this study achieved a multidisci-
plinary consensus aiming to pave the way for a better plan of treatment
for sinonasal malignancy by optimizing the poRT dose distribution.

Conclusion

This accurate atlas of structures identified during EESBS could serve for the poRT planning in patients with sinonasal tumors. It might allow, through careful planning of areas at risk of recurrence and adjacent organs to be preserved, to limit the morbidity of poRT while maintaining good local control. This precision-medicine approach would align with the limitation of morbidity allowed by EESBS in comparison with
craniofacial resection. Prospective studies are necessary to rigorously assess the morbidity and outcomes implications of this approach.

Funding

The authors did not receive any external funding.

## CRediT authorship contribution statement

**Florent Carsuzaa:** Writing – review & editing, Writing – original draft, Visualization, Validation, Resources, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.
**Valentin Favier:** Writing – review & editing, Writing – original draft, Validation, Formal analysis, Data curation.
**Lise Seguin:** Writing – original draft, Resources, Formal analysis, Data curation.
**Mario Turri-Zanoni:** Writing – review & editing, Validation, Investigation, Data curation.
**Anna-Maria Camarda:** Writing – review & editing, Validation, Formal analysis, Data curation.
**Benjamin Verillaud:** Writing – review & editing, Validation, Investigation, Data curation.
**Philippe Herman:** Writing – review & editing, Validation, Formal analysis, Data curation.
**Daniele Borsetto:** Writing – review & editing, Investigation, Data curation.
**Alberto Schreiber:** Writing – review & editing, Investigation, Data curation.
**Stefano Taboni:** Writing – review & editing, Investigation, Data curation.
**Vittorio Rampinelli:** Writing – original draft, Investigation, Formal analysis.
**Alessandro Vinciguerra:** Writing – review & editing, Investigation, Data curation.
**Alperen Vural:** Writing – review & editing, Investigation, Data curation.
**Xavier Liem:** Writing – review & editing, Investigation, Data curation.
**Fabio Busato:** Writing – review & editing, Investigation, Formal analysis.
**Sophie Renard:** Writing – review & editing, Investigation, Data curation.
**Charles Dupin:** Writing – review & editing, Investigation, Formal analysis.
**Mélanie Doré:** Writing – review & editing, Investigation, Data curation.
**Pierre Graff:** Writing – review & editing, Investigation, Data curation.
**Yungan Tao:** Writing – review & editing, Investigation, Data curation.
**Séverine Racadot:** Writing – review & editing, Investigation, Data curation.
**Antoine Moya Plana:** Writing – review & editing, Investigation, Formal analysis, Data curation.
**Basile N. Landis:** Writing – review & editing, Validation, Formal analysis.
**Pierre-Yves Marcy:** Writing – review & editing, Investigation, Data curation.
**Vincent Patron:** Writing – review & editing, Investigation, Data curation.
**Ludovic de Gabory:** Writing – review & editing, Validation, Formal analysis.
**Ester Orlandi:** Writing – original draft, Validation, Supervision, Methodology, Investigation, Data curation.
**Marco Ferrari:** Writing – original draft, Validation, Methodology, Investigation, Formal analysis, Data curation.
**Juliette Thariat:** Writing – review & editing, Writing – original draft, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.radonc.2025.110784.

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