Impact of overall treatment time during concurrent chemoradiotherapy for locally advanced NSCLC: An RTOG secondary analysis

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7061 Background/Purpose: To determine if overall treatment time is associated with outcomes after definitive concurrent chemoradiotherapy for locally advanced non-small cell lung carcinoma (NSCLC). Methods: Data were analyzed from three prospective Radiation Therapy Oncology Group (RTOG) trials (RTOG 91–06, 92–04, and 94–10) in which immediate concurrent chemoradiation (cisplatin-based) was the primary therapy for good-performance status Stage III (and selected inoperable Stage II) NSCLC. Protocol-specified radiotherapy was 63–69.6 Gy over approximately 6.5 weeks. Treatment time was analyzed as a continuous variable (in days) in a multivariate model that also incorporated histology, performance status, gender, age, stage, radiotherapy fractionation, and radiotherapy dose. Endpoints studied were overall survival, progression free survival (PFS), local-regional control and toxicity. Results: A total of 474 patients were analyzed. Median followup for surviving patients was 6.1 years. The multivariate model showed that prolonged treatment time was highly significantly associated with worsening overall survival (p=0.01) and PFS (p=0.02). The hazard ratio was 1.02 (95% confidence interval 1.00–1.03), reflecting an estimated 2% increase in the risk of death for each day of prolonged treatment. Histology and performance status were also significant prognosticators in this model (p=0.02 and p=0.03 for survival, respectively). A total of 87 patients (18%) had a treatment time that was prolonged ≥ 5 days beyond protocol specification; these patients had a median survival of 14.8 months, versus 19.5 months for other patients (p=0.15 by log rank). Although detailed data on the causes of treatment interruptions were not available, prolonged treatment time was strongly associated with high grade acute esophagitis (p<0.0001). Conclusions: This retrospective analysis demonstrates a negative association between prolonged overall treatment time and survival in patients treated with concurrent chemoradiation, supporting radiobiologic models. Further study of novel radiation-chemotherapy dose/fractionation regimens is warranted. No significant financial relationships to disclose.