Abstract 3852: Comprehensive genomic profiling of recurrent or metastatic head and neck cancer presenting with combined positive score 90 or more

Abstract Background. Biomarkers that predict response to immune checkpoint inhibitor (ICI) in recurrent metastatic squamous cell carcinoma of the head and neck (RMHNSCC) are not well known. Previously, we have found that Combined positive score (CPS) ≥90 and albumin >3.5 respond well to ICI treatment in patients with RMHNSCC treated with ICI irrespective of addition of chemotherapy. In the present study, we investigated whether RMHNSCC with CPS ≥90 has a characteristic genomic mutational profile. Methods. CPS measurements were performed on a single tumor specimen at the time of diagnosis of RMHNSCC, as approved by Japanese health insurance. Tumor specimens were obtained from the primary tumor as much as possible, and sections that best reflected anti-tumor immunity were decided by a pathologist. We retrospectively reviewed the results obtained from comprehensive genomic profiling (CGP) testing of RMHNSCC cases with CPS ≥90 who were treated by ICI experienced at our institution. Results. There were 117 eligible RMHNSCC cases. The number of primary lesions were oral cavity in 28 cases (23.9%), nasopharynx in 10 cases (8.5%), oropharynx in 21 cases (17.9%), hypopharynx in 33 cases (28.2%), and others in 18 cases (15.4%). Of 117 patients, 28 patients (23.9%) had a CPS ≥90. Of the 28 cases, the number of primary lesions were oral cavity in 12 cases (42.9%), nasopharynx in 4 cases (14.3%), oropharynx in 0 cases (0%), hypopharynx in 8 cases (28.6%), and others in 3 cases (10.7%). When ICI was administered, CPS ≥90 had a statistically significantly better prognosis than CPS <90 for OS and PFS. Of the 28 cases with CPS ≥90, CGP test was performed in 6 cases. The primary lesions in the 6 cases consisted of 3 oral cavity, 2 nasopharynx, 1 hypopharynx, and 1 maxillary sinus. All three oral primary cases had co-mutations in the TERT promoter and HRAS. Two of the nasopharyngeal primary cases had mutations in JAK3 and STAT, respectively. One of the hypopharyngeal primary cases had mutations in FGFR3. Conclusion. RMHNSCC with CPS ≥90 had unique mutations that could account the enhanced PD-L1 expression, such as TERT/HRAS co-mutation, JAK-STAT pathway mutation, and FGFR pathway mutation. The above findings may be useful for predicting the efficacy of ICI for RMHNSCC. Citation Format: Yuki Saito, Kage Hidenori, Kenya Kobayashi, Osamu Fukuoka, Koji Yamamura, Aya Shinozaki-Ushiku, Katsutoshi Oda, Kenji Kondo. Comprehensive genomic profiling of recurrent or metastatic head and neck cancer presenting with combined positive score 90 or more [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3852.