Background Radiotherapy (RT) is an effective treatment for elderly patients with locally advanced non-small-cell lung cancer (NSCLC); however, no clinical trials have investigated combination RT with pemetrexed (PEM) in chemotherapy-naive patients ≥71 years old. We conducted a phase I/II study to evaluate the appropriate PEM dose, efficacy, and safety of PEM plus RT in elderly patients. Methods Patients ≥71 years with performance status (PS) scores of 0-2 who had pathologically confirmed stage IIIA/IIIB NSCLC received PEM (500 mg/m2 on day 1 of a 28-day cycle, 4 courses) and RT (a single 2 Gy daily fraction on 5 consecutive days weekly from day 1; 60 Gy total). The primary endpoint was the objective response rate (ORR); the secondary endpoints were progression-free survival (PFS), overall survival (OS), and adverse events (AEs). Results Forty-one patients with a median age of 79 years were enrolled; 31 were men. Eighteen patients had squamous cell carcinoma, 27 had stage IIIA disease, and 38 had PS scores 0-1. The ORR was 80.5%, while the median OS and PFS rates were 24.9 and 6.9 months, respectively. Two treatment-related deaths occurred owing to RT-related pneumonitis and severe infection, respectively. Common hematological AEs were leucopenia and neutropenia; common non-hematological AEs were anorexia and constipation. Three patients developed PEM-induced interstitial lung disease; however, most AEs were RT-related. Conclusions Combination PEM and RT shows promising efficacy but relatively severe RT-related toxicities. Therefore, this treatment should be prescribed to elderly patients with caution. Trial registration UMIN 000005036 .
Keywords: Geriatric patients; Pemetrexed; Pneumonitis; Radiotherapy.