Clinicopathologic Factors and Their Association with Outcomes of Salivary Duct Carcinoma: A Multicenter Experience

Abstract

This series reports long-term clinical outcomes of patients with salivary duct carcinoma (SDC), which is associated with a poor prognosis. Eighty-nine patients with SDC were treated with curative intent from February 5, 1971, through September 15, 2018. Kaplan-Meier and competing risk analyses were used to estimate locoregional control, distant metastasis-free survival (DMFS), progression-free survival, and overall survival (OS). Cox regression analyses of disease and treatment characteristics were performed to discover predictors of locoregional control, DMFS, and OS. Median follow-up was 44.1 months (range, 0.23-356.67). The median age at diagnosis was 66 years (interquartile range, 57-75). Curative surgery followed by adjuvant radiation therapy was performed in 73 patients (82%). Chemotherapy was delivered in 26 patients (29.2%). The 5-year local recurrence and distant metastasis rates were 27% and 44%, respectively, with death as a competing risk. Distant metastasis was associated with lymph node-positive disease (hazard ratio [HR], 3.16; 95% confidence interval [CI], 1.38-7.23; P=.006), stage IV disease (HR, 4.78; 95% CI, 1.14-20.11; P=.033), perineural invasion (HR, 4.56; 95% CI, 1.74-11.97; P=.002), and positive margins (HR, 9.06; 95% CI, 3.88-21.14; P < .001). Median OS was 4.84 years (95% CI, 3.54-7.02). The 5-year OS was 42%. Reduced OS was associated with lymphovascular space invasion (HR, 3.49; 95% CI, 1.2-10.1; P=.022), perineural invasion (HR, 2.05; 95% CI, 1.06-3.97; P=.033), positive margins (HR, 2.7; 95% CI, 1.3-5.6; P=.011), N2 disease (HR, 1.88; 95% CI, 1.03-3.43; P=.04), and N3 disease (HR, 11.76; 95% CI, 3.19-43.3; P < .001). In this single-institution, multicenter retrospective study, the 5-year survival was 42% in patients with SDC. Lymphovascular space invasion, lymph node involvement, and higher staging at diagnosis were associated with lower DMFS and OS.