19503 Background: This study was performed to assess the value of combined modality therapy in elderly patients by comparing the differences in outcome of those who received radiotherapy (RT) alone or RT plus chemotherapy for stage III NSCLC. Methods: North Central Cancer Treatment Group (NCCTG) performed 2 recent phase III trials for stage III NSCLC. The first trial, 90–24–51, included 3 arms: once-daily radiotherapy (QDRT) alone, twice daily RT (BIDRT) alone, and concurrent chemotherapy plus BIDRT. The second trial, 94–24- 52 included 2 arms and compared concurrent chemotherapy with either QDRT or BIDRT. The chemotherapy arms of both trials included etoposide and cisplatin administered concurrently with RT. Only the patients ≥65 years of age (elderly) who participated in these trials were included in this analysis. Results: Of the 166 elderly patients included in this analysis, 37 received RT alone and 129 received concurrent chemotherapy plus RT. The median and 5-year survival rates were 10.5 months and 5.4% for the RT alone group compared to 13.7 months and 14.7% for the RT plus chemotherapy group (log-rank p=0.05). Patients who received RT plus chemotherapy experienced significantly greater severe (grade ≥3) toxicity than those who received RT alone (89.9% versus 32.4%, p < 0.01). Conclusions: Elderly patients who participated in these trials appear to gain a survival advantage from RT and chemotherapy compared to RT alone. As is the case with younger patients, this benefit comes at the cost of additional toxicity. No significant financial relationships to disclose.