Top Line: What factors are associated with better local control of colorectal cancer lung oligometastases treated with SBRT?
The Study: We recently saw in the phase 2 SAFRON II trial that single fraction SBRT to 1-3 lung oligometastases was comparable to multifraction SBRT at least a 1 year. However, a post-hoc analysis found that many of the recurrences in the single fraction arm were colorectal primaries. Other studies have also demonstrated lower control rates of colorectal cancer oligometastases. LaIT-SABR was a large, multicenter retrospective study from Italy of > 500 patients treated with SBRT for >1000 colorectal cancer lung oligometastases. Most (57%) had colon primaries and 43% had rectal primaries. Median BED10 was 105 Gy with 31% receiving < 100 Gy, 56% 100-124 Gy, and 13% > 124 Gy. Overall, freedom from local progression (FLP) was 86% at 1 year and 75% at 2 years. FLP at 2 years was 94% for lesions that received 125+ Gy BED compared to 76% for lesions that received < 100 Gy BED and 71% for 100-124 Gy BED. On multivariable analysis, BED > 124 Gy and tumor diameter < 2 cm were associated with better FLP. In addition, the risk of poly-metastatic progression was higher for lesions > 2 cm, patients with 4-5 metachronous lesions, and those who received < 125 Gy BED.
TBL: Higher BED, smaller lesion size, and a smaller burden of disease are associated with better local control for colorectal cancer lung oligometastases treated with SBRT. | Nicosia, Radiother Oncol 2021