Identification of oncological characteristics associated with improved overall survival in patients with adrenocortical carcinoma treated with adjuvant radiation therapy: Insights from the National Cancer Database

•aRT is recommended for patients with localized ACC at risk for recurrence.•In the NCDB, aRT is underutilized in indicated patients (18%).•aRT is associated with improved OS in aptients with PSM, large tumors, or high-grade disease•Limitations include registry data and missing data. To test for an association between oncological risk factors and overall survival in patients with non-metastatic adrenocortical carcinoma treated with adjuvant radiation therapy at high-risk for recurrence per NCCN guidelines. We analyzed data from patients undergoing surgical resection with or without aRT in the NCDB from 2004 to 2017. A multivariable Cox proportional hazards model was fit to assess for an association of aRT and OS. To determine whether aRT was associated with improved OS in patients with specific NCCN risk factors, we fit three multivariable Cox proportional hazard models with an interaction term between NCCN risk factors and the use of aRT. We identified 1,433 patients treated surgically for adrenocortical carcinoma with at least one risk factor. 259 patients received adjuvant radiation therapy (18%) while 1,174 (82%) patients did not. After adjustment, we noted a significant association between adjuvant radiation therapy and overall survival in the entire cohort in the multivariable Cox proportional hazards model (HR 0.68, 95% CI 0.55–0.85, P = 0.001). Adjuvant radiation therapy was associated with increased overall survival in patients with positive surgical margins (HR 0.47, 95% CI 0.35–0.65, P < 0.001), large tumor size ≥6 cm (HR 0.69, 95% CI 0.55–0.87, P = 0.002), and high-grade disease (HR 0.61, 95% CI 0.37–0.99, P = 0.046). Patients with ACC at high-risk for recurrence were associated with improved overall survival when treated with adjuvant radiation therapy. These data may help identify which patients should consider aRT after resection of clinically localized ACC.