Emily Guazzo1, Caroline Cooper2, Lisa Wilkinson3, Sophie Feng4, Brigid King5, Fiona Simpson5, Sandro Porceddu4,6, Benedict Panizza1,4,6, Jermaine I G Coward4,6,7. 1. Department of Otolaryngology, Head and Neck Surgery, Princess Alexandra Hospital, Brisbane, Australia. 2. Pathology Queensland, Princess Alexandra Hospital, Brisbane, Australia. 3. Sullivan and Nicolaides Pathology, Brisbane, Australia. 4. Division of Cancer Services, Princess Alexandra Hospital, Brisbane, Australia. 5. The University of Queensland Diamantina Institute, Princess Alexandra Hospital University of Queensland, Brisbane, Australia. 6. Faculty of Medicine, University of Queensland, Brisbane, Australia. 7. ICON Cancer Centre, Level 5, Mater Medical Centre, Brisbane, Australia.
Abstract
BACKGROUND: Data relating to the efficacy of immune checkpoint inhibitors (ICI) for salivary gland carcinomas (SGC) is gradually evolving with responses varying among different histotypes. To address these disparities, this retrospective analysis examined the prevalence of recognized biomarkers of response to ICI; namely programmed death-1 (PD-1), programmed death-ligand 1 (PD-L1), combined positive score (CPS), epidermal growth factor receptor (EGFR), and microsatellite instability (MSI) in patients with SGC with an aim to determine any prognostic or survival benefits and stratify the use of ICI in this disease. PATIENTS AND METHODS: Of 52 patients with primary SGC eligible for this study, the most common histological types were adenoid cystic carcinoma (n = 17, 33%), salivary duct carcinoma (n = 14, 27%), mucoepidermoid carcinoma (n = 11, 21%), and acinic cell carcinoma (n = 6, 11%). Immunohistochemistry (IHC) was performed using the Ventana Discovery Ultra auto-staining platform for EGFR, PD-1, PD-L1, and mismatch repair (MMR) proteins. CPS ≥1 defined PD-L1 positive cases and log-rank testing was performed to examine the relationship between PD-L1 expression status and disease-free survival (DFS) and overall survival (OS). RESULTS: CPS positivity was seen in 9 (17.3%) patients, none of which were adenoid cystic carcinoma. All 52 (100%) cases expressed retained MMR proteins inferring microsatellite stability (MSS) and EGFR expression was identified in 45 of 52 (86.5%) patients. CPS positivity (score ≥1) was significantly associated with advanced pathological T status (P = .021), advanced pathological N status (P = .006), high histological tumor grade (P = .045), and positive histological margin (P = .023). Patients with PD-L1 positivity in tumor cells did not have an inferior 3-year OS (P = .93). CONCLUSION: The data from this retrospective study highlighting the uniform microsatellite stability alongside the low prevalence of CPS positivity suggests that only a minority of SGC patients may benefit from ICI therapy alone. The high rates of EGFR expression in SGC may be a target to augment immune checkpoint therapy response.
BACKGROUND: Data relating to the efficacy of immune checkpoint inhibitors (ICI) for salivary gland carcinomas (SGC) is gradually evolving with responses varying among different histotypes. To address these disparities, this retrospective analysis examined the prevalence of recognized biomarkers of response to ICI; namely programmed death-1 (PD-1), programmed death-ligand 1 (PD-L1), combined positive score (CPS), epidermal growth factor receptor (EGFR), and microsatellite instability (MSI) in patients with SGC with an aim to determine any prognostic or survival benefits and stratify the use of ICI in this disease. PATIENTS AND METHODS: Of 52 patients with primary SGC eligible for this study, the most common histological types were adenoid cystic carcinoma (n = 17, 33%), salivary duct carcinoma (n = 14, 27%), mucoepidermoid carcinoma (n = 11, 21%), and acinic cell carcinoma (n = 6, 11%). Immunohistochemistry (IHC) was performed using the Ventana Discovery Ultra auto-staining platform for EGFR, PD-1, PD-L1, and mismatch repair (MMR) proteins. CPS ≥1 defined PD-L1 positive cases and log-rank testing was performed to examine the relationship between PD-L1 expression status and disease-free survival (DFS) and overall survival (OS). RESULTS:CPS positivity was seen in 9 (17.3%) patients, none of which were adenoid cystic carcinoma. All 52 (100%) cases expressed retained MMR proteins inferring microsatellite stability (MSS) and EGFR expression was identified in 45 of 52 (86.5%) patients. CPS positivity (score ≥1) was significantly associated with advanced pathological T status (P = .021), advanced pathological N status (P = .006), high histological tumor grade (P = .045), and positive histological margin (P = .023). Patients with PD-L1 positivity in tumor cells did not have an inferior 3-year OS (P = .93). CONCLUSION: The data from this retrospective study highlighting the uniform microsatellite stability alongside the low prevalence of CPS positivity suggests that only a minority of SGC patients may benefit from ICI therapy alone. The high rates of EGFR expression in SGC may be a target to augment immune checkpoint therapy response.