Long-term Follow-up on NRG Oncology RTOG 0915 (NCCTG N0927): A Randomized Phase 2 Study Comparing 2 Stereotactic Body Radiation Therapy Schedules for Medically Inoperable Patients With Stage I Peripheral Non-Small Cell Lung Cancer.

Purpose: To present long-term results of RTOG 0915/NCCTG N0927, a randomized lung stereotactic body radiation therapy trial of 34 Gy in 1 fraction versus 48 Gy in 4 fractions.

Methods And Materials: This was a phase 2 multicenter study of patients with medically inoperable non-small cell lung cancer with biopsy-proven peripheral T1 or T2 N0M0 tumors, with 1-year toxicity rates as the primary endpoint and selected failure and survival outcomes as secondary endpoints. The study opened in September 2009 and closed in March 2011. Final data were analyzed through May 17, 2018.

Results: Eighty-four of 94 patients accrued were eligible for analysis: 39 in arm 1 and 45 in arm 2. Median follow-up time was 4.0 years for all patients and 6.0 years for those alive at analysis. Rates of grade 3 and higher toxicity were 2.6% in arm 1 and 11.1% in arm 2. Median survival times (in years) for 34 Gy and 48 Gy were 4.1 versus 4.6, respectively. Five-year outcomes (95% confidence interval) for 34 Gy and 48 Gy were a primary tumor failure rate of 10.6% (3.3%-23.1%) versus 6.8% (1.7%-16.9%); overall survival of 29.6% (16.2%-44.4%) versus 41.1% (26.6%-55.1%); and progression-free survival of 19.1% (8.5%-33.0%) versus 33.3% (20.2%-47.0%). Distant failure as the sole failure or a component of first failure occurred in 6 patients (37.5%) in the 34 Gy arm and in 7 (41.2%) in the 48 Gy arm.

Conclusions: No excess in late-appearing toxicity was seen in either arm. Primary tumor control rates at 5 years were similar by arm. A median survival time of 4 years for each arm suggests similar efficacy, pending any larger studies appropriately powered to detect survival differences.