Adjuvant radiotherapy after primary surgical resection in patients with adrenocortical carcinoma: Retrospective cohort analysis.

Abstract

4641 Background: Adrenocortical carcinoma (ACC) is a rare malignancy with high recurrence and mortality rates. The role of adjuvant radiotherapy (RT) to improve outcome remains unclear. Considering the rarity of ACC, we conducted a historical cohort study to ascertain the effect of adjuvant RT on overall survival and recurrence rates. Methods: Patients were selected from the MD Anderson Cancer Center (MDACC) ACC registry (1998- 2011) who had primary tumor resection with no evidence of distant metastasis at the time of initial diagnosis and a minimum follow-up of 6-months. The adjuvant RT group included patients who received adjuvant RT within 3 months of diagnosis. Control group included patients who did not receive RT and matched based on resection margin status and stage at diagnosis. Results: There were no significant differences between the adjuvant RT group (n=15) and comparison group (n =45) in gender distribution, age, tumor size, functional status, and use of adjuvant mitotane therapy. On multivariate Cox proportional hazard model for overall survival, the adjuvant RT group had hazard ratio of 1.981(95% confidence interval [CI] 0.894-4.391, p=0.0922) compared to the control group. The differences in median time to local recurrence, distant recurrence and of recurrence free survival were not significant between the two groups. In subgroup analysis including only the patients whose initial treatments were from outside of MDACC, RT group (n=15) had hazard ratio of overall survival of 1.604 (95% CI 0.712- 3.613, p=0.2543) compared to group without adjuvant RT (n= 32). Median times to local recurrence, distant recurrence, or of recurrence free survival were also not significantly different between the two groups. Conclusions: To our knowledge, this is the largest single institution report about adjuvant RT use in ACC. In our study, RT did not appear to cause a significant difference in overall survival, recurrence rate, or time to recurrence. However, it is still possible that patients offered adjuvant RT and control groups may have been inherently different. Hence, a prospective study is needed to clarify the role of adjuvant RT in patients with resectable ACC.