Long term control stereotactic body radiotherapy (SBRT) for oligometastatic colorectal cancer: a single center study.

Background: To evaluate survival after stereotactic body radiotherapy (SBRT) as radical treatment for metastases of colorectal cancer (CRC) and to identify prognostic factors after treatment.

Methods: Patients with metastatic CRC treated with SBRT on metastatic lesions were retrospectively analyzed between February 2012 and August 2016 at the General University Hospital of Valencia. The follow-up was carried out until July 15, 2018. The data have been collected in a database. Patients may have received prior systemic therapy and/or resection of metastatic disease. Endpoints were timed from end of SBRT and included overall survival (OS) and progression-free survival (PFS). Univariate and multivariate analysis using Cox proportional hazard modeling was used to identify prognostic factors.

Results: A total of 49 patients were identified. Before SBRT, 77.5% of the patients have received systemic therapy and 65.2% surgery for metastatic disease. Of metastatic lesions treated with SBRT 53.1% were located in the lung, 30.6% in the liver and 16.3% in other locations. Median survival were: PFS after treatment with SBRT was 9.9 months (95% CI: 4.64-15.1) and the median OS was 28.9 months (95% CI: 19.0-38.7). No relapses were observed in 20% of the patients after SBRT. The treatment was well tolerated and no patient had grade 3 or 4 adverse effects. Right colon [HR 16.53 (95% CI: 3.11-87.87), P value 0.001] and higher tumor stage (III-IV) [HR 12.30 (95% CI: 2.10-71.92), P value 0.005] showed a lower OS in a multivariate analysis.

Conclusions: SBRT for oligometastatic disease is an effective option for patients with advanced CRC, with encorauging survival outcomes. However, a definitive validation in large randomized studies is required.