SSTR2 use and molecular profile in EBV-positive nasopharyngeal carcinoma: A single institution experience

Abstract Background: Nasopharyngeal carcinoma (NPC) is a rare malignancy endemic in Southeast Asia. EBV infection is recognized as a major risk factor playing important roles in oncogenic pathways. Somatostatin receptor 2 (SSTR2) is a marker used in neuroendocrine tumors and appears to demonstrate high prevalence in EBV+ NPCs. Methods: We identified a total of 16 patients with biopsy-proven WHO type 3 EBV+ (via EBER) NPC in which SSTR2 expression via immunohistochemistry (IHC) was analyzed in either primary or metastatic lesions. Additionally, risk factors (smoking or alcohol), P16 via IHC, PD-L1 via IHC, tumor mutation burden (TMB), microsatellite instability (MSI), genomic alterations via Next Generation Sequencing (NGS), and time to progression (TTP) in months were reported. Results: Mean age of diagnosis was 60 years old, 14 were male, 13 were locally advanced and 37.5% former or heavy smokers. Ten patients were Asian with the rest being Latino (4), European (1) and unknown (1). Fourteen out of sixteen patients (87.5%) had SSTR2 expression either in primary lesions or metastatic lesions. P16 was measured in seven cases, all of them being negative. PDL1 was measured in 11 cases, 9 had high expression (≥ 20 CPS), 2 had expression (1-19 CPS) and 5 was not measured. In 10 cases TMB was evaluated, seven had low TMB and three intermediate TMB. From the TMB intermediate cases, all of them were MSI stable and two high PDL1 expression. From the 10 patients with MSI status all of them were stable. Out of the 16 patients, 11 patients had NGS performed from which 9 patients had clinically significant alterations. 4 out of 9 patients (44.4%) had an 11q13.2-13.3 amplification followed by 33.3% having a 9p21 loss and 22.2% TP53 mutation. Survival, median survival was not reached and median TTP was 23 months with the most common site being the liver. Conclusions: Given the high prevalence of SSTR2 in EBV+ NPCs (87.5%) in our cohort, SSTR2 via IHC may be a good screening tool for EBV + NPCs with potential diagnostic and therapeutic implications. 11q amplifications being present in 44.4% of our cohort might also be of diagnostic significance in NPC. Prognostic and clinical implications warrant further investigation. Citation Format: Juan J. Juarez-Vignon Whaley, Michelle Afkhami, Mykola Onyshchenko, Thomas Gernon, Robert Kang, Ellie Maghami, Sagus Sampath, Arya Amini, Diana Bell, Victoria M. Villaflor. SSTR2 use and molecular profile in EBV-positive nasopharyngeal carcinoma: A single institution experience [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-016.