FLARE-RT PET/SPECT-guided risk-adaptive RT boosts durability of locoregional control in unresectable NSCLC

FLARE-RT (Phase II; NCT02773238) tested biological image-guided chemoradiation for AJCCv7 stage IIB–IIIB unresectable NSCLC (n=49), combining functional lung avoidance (SPECT/CT) with mid-treatment FDG-PET response adaptation: week-3 PET responders received 60Gy/30 fx, while non-responders received a concomitant PET-guided boost to 74–90Gy total. With 52.3 months median follow-up, 1- and 2-year OS were 81.6% and 54.2%, and 1- and 2-year PFS were 53.1% and 40.5%; 2-year cumulative incidence of locoregional progression (LRP) was 18.5% while distant metastasis (DM) remained the dominant failure mode at 43.1% (2-year). These survival results look broadly in-family with historical concurrent CRT benchmarks like RTOG 0617 (60Gy arm mOS 28.7 months; 5-year OS 32.1%), while the key signal here is durable LRP control despite selective escalation (and without the uniform 74Gy strategy that performed worse in RTOG 0617); durvalumab use (25/49) was associated with lower 1-year DM (20.0% vs 54.2%, p=0.04), aligning directionally with the PACIFIC-era standard where consolidation durvalumab improves OS and long-term PFS versus placebo after CRT. Take Home: If this PET-response-adaptive strategy can be validated in larger, multi-center testing, it’s a rational way to “spend dose where it matters” to sustain local control—while the still-high DM rates (and the non-randomized durvalumab split) reinforce that systemic therapy optimization remains the main lever for further gains in unresectable stage III disease.