Long-term outcomes and clinicogenomic correlates in recurrent, metastatic adenoid cystic carcinoma

Background: Little is known about the long-term impact of local and systemic therapies for recurrent/metastatic (R/M) adenoid cystic carcinoma (ACC), or the clinical significance of molecular alterations. Methods: We identified 72 R/M cases among 123 ACC patients from our institution. We report long-term outcomes, predictors of recurrence and survival, and the impact of sequential cancer-directed therapy among R/M patients. We integrate genomic data for 36 sequenced ACC patients. Results: Median overall survival (OS) from initial diagnosis was 35.1 ys (95%CI: 25.8-37.3) for R/M ACC patients. 10-y OS among R/M patients was 84.7%, worse for patients with extra-pulmonary metastatic disease (p = 0.02). Only initial disease stage predicted recurrence (OR 1.69, p = 0.03). Longer time to first R/M treatment predicted improved survival (p < 0.01); those treated <= 3 years from their R/M diagnosis had poor outcomes (p = 0.01). R/M patients who received systemic therapy vs. active surveillance had similar survival (p = 0.35). Molecular findings predicted outcomes: 10-y OS: 100% MYB, 53.3% PI3K, 32.1% NOTCH1 and others, p = 0.03. PI3K mutations predicted a longer disease-free interval (p = 0.04). Conclusions: Underlying disease biology remains the strongest predictor of outcomes in R/M ACC. Shorter time to R/M therapy predicts poor outcomes. Molecular alterations are prognostic, and PI3K mutations identify an intermediate-risk ACC subgroup.