Abstract 03: Imaging characteristics of head and neck tumors according to human papillomavirus (HPV) status in Bogotá, Colombia
Authors: Useche Nicolás , Torres Oscar , Rojas Maria M. , Palau-Lázaro Mauricio , Mejía-Arango Marcela , Baldión Ana Margarita , Hakim José A. , Campos Johanna , Escallon Alberto , Ospina Aylen Vanessa , Perdomo Sandra , Rodríguez-Urrego Paula A. 
Published: December 2017

Abstract
Background: HPV-positive head and neck tumors (HNT) correspond to a unique entity given their clinical behavior and molecular characteristics. These tumors can show distinct features on pretreatment imaging, such as well-defined borders and cystic nodal metastases; therefore, the aim of our study was to evaluate the imaging characteristics and determine if there are differences between HPV-positive and HPV-negative HNT tumors in patients studied at our institution.
Design: A retrospective pretreatment imaging review from 35 HNT cases recruited under INTERCHANGE- IARC project in Latin America between 11-2014 and 12-2016 was performed. Imaging evaluation included primary lesion and nodal metastases. Initial evaluation by radiologists was blinded for patients' histological findings and HPV status. Radiology was evaluated for: location, tumor size, tumor border morphology, contrast enhancement, nodal metastases, size of metastasis and morphology of nodal metastasis. Radiological findings were correlated with histology and p16 INK4a inmunohistochemistry using clone E6H4 (HPV surrogate marker).
Results: Pretreatment images were available for review only in 17 of 35 cases (48,5%). 10 cases had computerized tomography (CT) examination, 1 case magnetic resonance (MR) and 6 cases had 18F-FDG PET-CT. 6/17 cases (35.3%) were excluded due to no visualization of the primary tumor or due to limitation artifacts (amalgam). From the 11 cases available for review, 7 were from the oropharynx (OP), 2 from the oral cavity (OC) and 1 from the larynx (LA). All OP tumors were positive for p16 and all the rest tumors were p16 negative. Tumor size ranged from 7 to 51 mm in greatest dimension. Well-defined borders were present in 4/7 p16 positive tumors vs 2/4 p16 negative tumors. Tumor enhancement with contrast was present and able to evaluate only in 5 out of 11 tumors (3 p16 + and 2 p16 -). All the OP p16 positive tumors presented with nodal metastasis greater than 10 mm in dimension. 6/7 had nodal cystic change and these p16 positive cases were more likely to have large cystic nodal metastases with a cystic component larger than 50% of the nodal size (6/7) than p16/HPV negative tumors (1 out of 4 cases had smaller nodal metastasis with cystic component &lt;50%).
Conclusion: Large nodal metastasis (&gt;10 mm) with cystic component larger than 50% of the node size is an important finding seen in p16 HNT. One should consider these findings when examining neck images in patients with unknown primary in order to exclude malignancy given that usually cystic nodes could be misdiagnosed as benign. Our nondiagnostic imaging rate pretreatment was 35%; in order to improve the use of diagnostic tools we recommend the use of MR especially in patients with amalgams and/or tumor located at the oral cavity and oropharynx. Further studies are granted with a larger sample size in order to validate and confirm imaging characteristics in p16/HPV positive HNT.
Citation Format: Nicolás Useche, Oscar Torres, Maria M. Rojas, Mauricio Palau-Lázaro, Marcela Mejía-Arango, Ana Margarita Baldión, José A. Hakim, Johanna Campos, Alberto Escallon, Aylen Vanessa Ospina, Sandra Perdomo, Paula A. Rodríguez-Urrego. Imaging characteristics of head and neck tumors according to human papillomavirus (HPV) status in Bogotá, Colombia [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; April 23-25, 2017; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(23_Suppl):Abstract nr 03.