Abstract P1-21-02: Scalp sparing whole-brain radiotherapy using IMRT technique. Do we need it?
Authors: Barsoum Mohsen Samy , Barsoum Emad Mohsen , Kamaleldin Maha , Mahmoud Niven , Abdelgeleel Shaimaa , Ashour May Gamal 
Published: March 2022

Introduction: The prognosis of metastatic breast cancer patients is improving due to advances in systemic therapy, which led to better control of the disease. Brain metastasis that requires whole-brain radiotherapy (WBRT) is mandatory for some patients.Acute alopecia is a common side effect, and total hair loss occurs in 100% of patients receiving parallel opposed direct laterals fields.Because of the recognized reduction in quality of life associated with clinically apparent and clinically undetectable hair loss, efforts are made to minimize hair loss resulting from WBRT.It is theorized that intensity-modulated radiotherapy (IMRT) may reduce hair loss. It will be less patchy because IMRT enables dose modulation, minimizing the radiation dose received by the hair follicles in the scalp.This dosimetric study assessed the dose received to the whole scalp and its subvolumes by three radiotherapy techniques. Methods: A total of 30 treatment plans for ten patients receiving WBRT were evaluated retrospectively. All patients were simulated in a supine position with a thermoplastic mask. The scalp was contoured as 5 mm between the skin and the outer table of the skull. Then we subdivided the scalp volume into superior, anterior, lateral, and posterior subvolumes. The dose prescribed was 30 Gy in 10 fractions. We compared three different radiotherapy techniques using the standard WBRT procedure that involves applying two lateral opposing fields (OF-WBRT) with a margin surrounding the brain, which includes the hair follicles situated about 5 mm. below the scalp, the field in field (FiF), and IMRT techniques without introducing the scalp in the optimization process using 6 MV photon energy. Results: All techniques showed comparable PTV coverage. The homogeneity index with opposed lateral was 0.057±.09, 0.057±.0111 for FiF, and 058±.0114 for IMRT with no statistically significant difference (p = 0.407).IMRT resulted in a marked decrease in all scalp parameters with a statistically significant difference, with a little difference in the dose delivered to lateral subvolumes. (table 1)

Conclusion: Scalp sparing IMRT for WBRT reduces the scalp dose compared to conventional WBRT, especially in the superior, anterior and posterior axis. Further randomized prospective trials are needed to confirm this benefit. 2

Table. PTV coverage and dose to the scalp and its subvolumes.characteristicsOPPOSED LATERALFIFIMRTP-ValueMean ± SDMean ± SDMean ± SDAll groupsOpposes lateral/FIFOpposes lateral/IMRTIMRT/FIFPTV D 98%96.9±0.796.9±0.797.1±0.71.000Scalp mean dose (cGy)2165.7±270.52120.5±242.81385.9±306.7&lt;0.0010.076&lt;0.0010.076Scalp V 20 (%)68.4±12.567.1±11.237.6±11.2&lt;0.0010.221&lt;0.0010.042Superior mean dose (cGy)2396.8±138.92326.1±1211419.0± 372.4&lt;0.0010.076&lt;0.0010.076Anterior mean dose (cGy)2180.9±237.82209.7±205.01267.4±462.2&lt;0.0010.221&lt;0.0010.042Lateral mean dose (cGy)2127.7±252.62136.9±249.12071.4±257.10.0020.2210.2210.001Posterior meanDose (cGy)2317.8±205.62273.3±207.81467.2±209.7&lt;0.0010.0760.076&lt;0.001

Citation Format: Mohsen Samy Barsoum, Emad Mohsen Barsoum, Maha Kamaleldin, Niven Mahmoud, Shaimaa Abdelgeleel, May Gamal Ashour. Scalp sparing whole-brain radiotherapy using IMRT technique. Do we need it? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-21-02.