Impact of Anatomic Site of Distant Metastasis on Survival in Salivary Gland Cancers

BACKGROUND: As exemplified in patients with adenoid cystic carcinoma (ACC), metastatic salivary gland cancers display heterogenous behavior. Although anatomic site of metastasis has been suggested to be prognostic for survival in this population, this is not adequately characterized in the current literature. METHODS: Using the National Cancer Database (NCDB), patients with newly diagnosed metastatic salivary gland cancers with distant metastasis to a single organ were identified. RESULTS: Eight hundred and fifty-eight patients (n = 284 bone-only, n = 322 lung-only, n = 252 other-site-only) were identified. Anatomic site of distant metastasis was not associated with survival in the cohort as a whole; however, on pre-planned subgroup analysis, lung-only metastasis, relative to bone-only metastasis, was the only factor associated with improved survival in patients with ACC (HR: 0.52, 95%CI: 0.30-0.93, p = 0.029). CONCLUSIONS: Anatomic site of metastasis is strongly associated with survival in patients with metastatic ACC and should be considered in future studies aiming to optimize therapy in this population.