Top Line: Is single-fraction SBRT a safe and effective option for treating uncomplicated lung oligometastases?
The Study: In the phase 2 TROG SAFRON II trial, 90 patients with 1-3 non-central lung metastases that were ≤ 5 cm were randomized to SBRT with 48 Gy in 4 fractions or 28 Gy in 1 fraction. As a reminder, similar comparisons have been made for definitive SBRT but with a higher single fraction dose of 34 Gy x 1. The purpose was to determine if there was increased toxicity with single fraction SBRT. At 1 year, there was no difference in the rate of grade 3+ toxicity with single fraction (5%) compared to multi-fraction SBRT (3%). The only grade 5 event (radiation pneumonitis) occurred in a multi-fraction patient treated for 3 metastases who had unrecognized interstitial lung disease. Freedom from local failure at 1 year was 93% for single fraction SBRT and 95% for multi-fraction SBRT. At 2 years, FFLF split to 73% vs 83%, and at 3 years it was 64% for single-fraction and 80% for multi-fraction SBRT. A post-hoc analysis found that many of the local failures in the single-fraction arm were colorectal cancer primaries. One question is whether a higher single-fraction dose, which is safe in definitive lung cancer trials, might improve control beyond 1 year.
TBL: Single-fraction SBRT to up to 3 non-central pulmonary targets appears as safe as multi-fraction SBRT with comparable efficacy out to 1 year. | Siva, JAMA Oncol 2021