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

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

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.

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.

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.