Survival Outcomes and Prognostic Factors of Primary Salivary Gland Malignancy: A 24-Year Retrospective Cohort Study.
BACKGROUND Salivary gland malignancy (SGM) is a rare and heterogeneous head and neck neoplasm. Curative treatment often mandates upfront surgery. Patients with high-risk features receive adjuvant radiotherapy. This study aims to investigate the clinicopathological characteristics, survival outcomes and prognostic factors for primary SGM in an Australian population. METHODS A retrospective cohort study of adult patients with primary SGM diagnosed between January 2001 and December 2024 at our institution was conducted. Clinicopathological and treatment characteristics were collected. Overall survival (OS), recurrence-free survival (RFS) and disease-free survival (DFS) were calculated. Log-rank univariate analysis and multivariate Cox regression analysis were conducted to determine prognostic factors for OS and DFS. RESULTS A total of 149 patients were included. The median follow-up time was 59 months (IQR 22.75-96 months). Patients were mostly male (57.7%) with a median age of 59 years (IQR 48-71 years). Tumours were most commonly located in the parotid gland (81.2%). The most common histological subtype was mucoepidermoid carcinoma (26.2%). The 5- and 10-year OS, RFS and DFS were 81.9% and 77.9%, 78.5% and 71.8% and 84.6% and 82.6%, respectively. Independent prognostic factors for OS were ECOG 2/3 (HR 19.059, 95% CI [3.061-118.664]), T3/4 (HR 6.925 [2.871-16.703]) and intermediate/high grade (HR 3.310 [1.122-9.761]). Independent prognostic factors for DFS were ECOG 2/3 (HR 64.267 [7.758-532.400]), T3/4 (HR 8.085 [3.008-21.729]) and intermediate/high grade (HR 8.065 [1.774-36.660]). CONCLUSIONS Survival outcomes for primary SGM significantly differ between subtypes. Independent prognostic factors for OS and DFS are ECOG 2/3, T3/4 and intermediate/high grade.