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

Background

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.

Methods

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.

Results

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.

Conclusion

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.