Brief Report: Mature Outcomes of 61.2 Gy Concomitant Boost Thoracic Radiotherapy in Limited Stage Small Cell Lung Cancer: CALGB 30610 (Alliance) / RTOG 0538.

Abstract

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