Local failure common in metastases from right-sided primary CRC treated with SABR

Local failure (LF) is more likely to occur in colorectal cancer (CRC) metastases treated with stereotactic ablative radiotherapy (SABR) if originating from right-sided primary CRC compared with left-sided, a study has found. In addition, LF rates are highest with liver metastases than other metastatic sites.

A team of investigators performed a retrospective review of patients with CRC metastases to the brain, liver, spine, or lung treated with SABR between 2001 and 2016. In addition, they summarized time to LF using the cumulative incidence of LF curves with death as a competing risk.

Overall, 130 patients and 256 lesions were included in the analysis. Of the metastases treated, 129 (50 percent) were brain, 50 (20 percent) liver, 49 (19 percent) spine, and 28 (11 percent) lung. Median gross tumour volumes were 24, 2, 4, and 1 mL for liver, brain, spine, and lung metastases, respectively.

The overall cumulative incidence of LF rates was 21.5 percent at 1 year, 28.2 percent at 2 years, and 31.5 percent at 3 years. LF was highest among metastases of the liver (1 year: 26.0 percent; 2 years: 38.5 percent), followed by spine (1 year: 25.1 percent; 2 years: 31.1 percent), brain (1 year: 20 percent; 2 years: 25.2 percent), and lung (1 year: 13.7 percent; 2 years: insufficient data).

LF was significantly more likely to occur in metastases from right-sided primary CRC (hazard ratio, 2.23; p=0.0146). Other significant predictors of LF were biologically effective dose >70 Gy (defined using a standard linear quadratic model using α/β ratio of 10 on the individual lesion level; p=0.0009) and pre-SABR chemotherapy (p=0.018).

“CRC liver metastases and metastases from right-sided CRC may benefit from more aggressive radiotherapy,” the investigators said.