Mature Outcomes of 61.2 Gy Concomitant Boost Thoracic Radiation Therapy in Limited-Stage Small Cell Lung Cancer: CALGB 30610 (Alliance)/RTOG 0538

Purpose: We report mature outcomes of patients with limited-stage small cell lung cancer randomly assigned to the 61.2 Gy concomitant boost (CB) thoracic radiation therapy (TRT) arm of Cancer and Leukemia Group B (CALGB) 30610/Radiation Therapy Oncology Group (RTOG) 0538. The CB arm was discontinued after planned interim analysis; however, the study provides the largest prospective data set using 61.2 Gy CB TRT. Methods and Materials: Eligible patients had limited-stage small cell lung cancer with regional lymph node involvement and Eastern Cooperative Oncology Group performance status 0 to 2. TRT began with either the first or second (of 4 total) cycle of cisplatin-based chemotherapy. Three-dimensional conformal radiation therapy or intensity modulated radiation therapy planning was required. In the initial phase of the trial, patients were randomly assigned with a 1:1:1 allocation to 45 Gy twice daily, 70 Gy once daily, and 61.2 Gy CB TRT. Results: Ninety-three patients were assigned to receive 61.2 Gy CB TRT. After a median follow-up of 115 months for surviving patients, median overall survival and progression-free survival were 32.3 months (95% CI, 20.4-44.8 months) and 15.4 months (95% CI, 10.0-24.0 months), respectively. Five-year overall survival was 28.5% (95% CI, 20.6-39.6). Rates of grade 3 and 4 nonhematologic adverse events were 40.9% and 25%, including 16% dysphagia and 7% severe pulmonary toxicity. Conclusions: CB TRT outcomes appear similar to contemporaneous trials using 45 Gy twice-daily or high-dose once-daily TRT and compare favorably with prior phase 2 data. Improved outcomes highlight the impact of advances in staging and radiation therapy techniques, although additional factors may have contributed.