The Study: It’s a great treatment with a great rationale, in terms of both biologically-effective dose and patient convenience. The problem is there is a serious lack of phase 3 data. Or there was. The Aussie phase 3 CHISEL trial successfully enrolled over 100 patients with peripheral early-stage (aka ≤cT2aN0, aka ≤4 cm) NSCLC who were not offered (n=89) or who declined (n=12) surgery. They were then randomized 1:2 to  conventional radiation to 2.5 Gy x 20 (n=10) or 2 Gy x 33 (n=23) per institutional preference versus  SBRT to 18 Gy x 3 (n=8) or 12 Gy x 4 (n=56) with four fractions prefered if the target was within 2 cm of chest wall. Based on single-arm series, the authors boldly estimated the primary endpoint of local control at 2 years to be quite different between the two arms at 70% with conventional radiation versus 90% with SBRT. Well, they were pretty spot-on as those rates were, in fact, 65% versus 89%. Grade 3-4 toxicities occurred in 3 patients receiving conventional radiation versus 8 receiving SBRT, though the authors note the latter had 2.3x the cumulative follow-up time. That’s because median overall survival was 3 versus 5 years. This distinction in survival with SBRT is a first. Perhaps because enrollees, with mandatory upfront negative PET staging and ECOG status ≤1, lived long enough to see it.
Bottom Line: SBRT has chiseled out a role in peripheral early-stage NSCLC by improving local control when compared to conventional radiation, translating to longer survival when the treated cancer is a patient’s biggest problem. | Ball, Lancet Oncol 2019