(626) Immunotherapy for Advanced Salivary Gland Cancers: A National Cohort Analysis

Introduction: Management of metastatic salivary gland cancers (M-SGC) present a clinical challenge with limited efficacy of standard therapeutic modalities. Although recent clinical trials show that immunotherapy may improve control of M-SGC, survival outcomes in patients receiving immunotherapy outside of trials remain underexplored. This study aimed to assess the clinical outcomes of non-palliative immunotherapy for M-SGC patients using the National Cancer Database (NCDB).

Methods: A cohort study was conducted using data from the NCDB; M-SGC patients (N=891) who received immunotherapy from 2013 to 2020 were identified. The primary endpoint was overall survival (OS) following diagnosis stratified by immunotherapy use and secondary endpoint was evaluating effects of treatment, insurance, treatment facility, and demographics on OS. Kaplan-Meier and multivariable Cox regression were used for analysis.

Results: Among 891 M-SGC patients (average age, 67.4 years (±13.71)), there were 104 adenoid cystic carcinoma, 51 mucoepidermoid carcinoma, 21 carcinoma in pleomorphic adenoma; 618 male [69.3%], 110 (12.3%) received immunotherapy and 781 (87.7%) who did not. Immunotherapy use increased from 2013-2014 compared to 2019-2020 (7.65% vs 21.05%; R2=0.056). M-SGC patients receiving chemotherapy and immunotherapy had the highest 5-year OS (22.1%; 95% CI, 11.6-41.8%) compared to patients receiving only chemotherapy (16.3%; 95% CI, 12.1-22.0%). Multivariable Cox analysis revealed M-SGC patients treated with chemotherapy and immunotherapy had improved OS compared to patients treated with chemotherapy alone (HR, 0.55; 95% CI, 0.39-0.78).

Conclusions: This study demonstrates increased immunotherapy use from 2013 to 2020 and a significant survival benefit to adding immunotherapy to chemotherapy for M-SGC patients.