Short course radiation as a component of definitive multidisciplinary treatment for select patients with metastatic rectal adenocarcinoma

Background: Select patients with rectal adenocarcinoma with metastatic disease at presentation can be cured with multimodality management. However, the optimal components and sequencing of therapy is unknown. The aim of this study is to evaluate outcomes for patients treated with chemotherapy, short course radiation therapy (SCRT) and surgical resection. Methods: Patients with newly diagnosed metastatic rectal adenocarcinoma who received SCRT from 2010-2016 were identified. All patients were evaluated by a multidisciplinary team and deemed candidates for treatment with curative intent. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method. Patient, tumor and treatment characteristics were evaluated as prognostic factors using a Cox proportional hazards model. Results: Thirty-four patients were included with a median [interquartile range (IQR)] follow-up of 25 (14.75-42.25) months; 26 patients (76.5%) received definitive surgery for their rectal tumor, and 24 patients (70.6%) received definitive local management of metastatic disease. One-, 2- and 3-year OS were 97%, 86.2% and 76.0%, respectively, and 1-, 2-, and 3-year PFS were 52.1%, 22.7% and 17%, respectively. On multivariate analysis, definitive management of metastases was associated with improved OS [hazard ratio (HR) 0.03, 95% confidence interval (CI): 0.01-0.33]; P=0.003, and =≤ months of neoadjuvant chemotherapy was associated with decreased OS (HR 11.7, 95% CI: 2.11-106; P=0.004). Conclusions: These findings suggest that SCRT can be successfully integrated into a definitive, multidisciplinary approach to metastatic rectal adenocarcinoma. Benefits to this approach include decreased time off systemic therapy as compared to standard course RT. Further study is needed to determine the optimum interval between SCRT and surgery.