Survival outcomes of pulmonary metastasis-directed local therapy in adenoid cystic carcinoma.

Abstract

Adenoid cystic carcinoma (ACC) frequently has pulmonary metastasis (PM). Given limited systemic therapy options, these metastases are often treated with pulmonary metastasis-directed local therapy (PM-LT), although with unknown impact on overall survival (OS). This single institution, retrospective cohort study investigated the survival outcomes of PM-LT versus no PM-LT in ACC. ACC patients with at least one PM (≥5 mm) were included. PM-LT was metastasectomy or radiotherapy. Clinicopathologic characteristics were compared between patients with and without PM-LT. Primary end point was OS from PM diagnosis, with landmark analysis at 6 months, 1 year, 2 years, and 3 years after metastasis diagnosis, with Cox proportional hazards model multivariate analysis and propensity score matching analysis. Subgroup analysis by ACC histology (solid/nonsolid) was performed. Of 219 included ACC, 119 (54%) had no PM-LT and 100 (46%) did. PM-LT patients had more nonsolid histology (p = .0008), oligometastases (p < .0001), exclusively PM (p = .02), and longer time to metastasis from diagnosis (p < .0001). On univariate analysis, PM-LT by 6 months, 1 year, and 2 years, but not by 3 years, increased OS. On multivariate analysis, PM-LT by 6 months (p = .12), 1 year (p = .08), or 3 years (p = .08) did not significantly increase OS, but PM-LT by 2-years had a borderline statistically significant association (p = .045). Of the 104 nonsolid ACC, 50 underwent PM-LT and 54 did not. On univariate and multivariate analysis, PM-LT did not increase OS at any time point for nonsolid ACC. This is the largest study of survival outcomes of PM-LT in metastatic ACC. Findings suggest PM-LT does not increase OS in unselected ACC.