Predicting the benefit of stereotactic body radiotherapy of colorectal cancer metastases

Abstract

AimTo evaluate Stereotactic body radiotherapy (SBRT) in metastatic colorectal cancer (mCRC) and identify the benefit of the treatment by using a predictive algorithm. Methods85 patients treated with SBRT for mCRC were retrospectively analyzed. The CLInical Categorical Algorithm (CLICAL©) was used to predict probability of relapse after SBRT. Variables pre-SBRT were tested for significance for time to relapse (TTR). The patients’ CLICAL© score was the mean of sub-scores of each significant variable’s effect on the endpoint. Patients with similar scores were grouped into four signatures dependent on level of benefit after SBRT. ResultsMedian age was 69 years (42–88), 63 % had a performance status 0 and 47 % were treated for a single metastasis. At the time of the analysis, 90 % had relapsed (95 % out-of-field). Median TTR was 7.3 months (4.6–8.5), and the 2-year relapse-free rate was 15 % (95 %CI = 7–22). The CLICAL© signature III-IV predicted a low risk of relapse if receiving high dose SBRT to all metastases or to lung metastases only. Signature I-II had a short TTR, why SBRT for these patients was judged non-beneficial. ConclusionThe benefit from SBRT varies among mCRC patients. CLICAL© may serve as a screening tool for SBRT referrals but needs to be validated.