Results of Proton Beam Therapy without Concurrent Chemotherapy for Patients with Unresectable Stage III Non-small Cell Lung Cancer

Introduction: This study was performed retrospectively to evaluate the outcome of patients with stage III non-small cell lung cancer (NSCLC) after proton beam therapy (PBT) alone. Methods: The subjects were 57 patients with histologically confirmed NSCLC (stage IIIA/IIIB: 24/33) who received PBT without concurrent chemotherapy. The cohort included 32 cases of squamous cell carcinoma, 18 adenocarcinoma, and 7 non-small cell carcinoma. Lymph node metastases were N0 7, N1 5, N2 30, and N3 15. Planned total doses ranged from 50 to 84.5 GyE (median, 74 GyE). Results: Planned treatment was completed in 51 patients (89%). At the time of analysis, 20 patients were alive, and the median follow-up periods were 16.2 months for all patients and 22.2 months for survivors. The median overall survival period was 21.3 months (95% confidence interval: 14.2-28.4 months), and the 1- and 2-year overall survival rates were 65.5% (52.9-78.0%) and 39.4% (25.353.5%), respectively. Disease progression occurred in 38 patients, and the 1- and 2-year progression-free survival rates were 36.2% (23.1-49.4%) and 24.9% (12.7-37.2%), respectively. Local recurrence was observed in 13 patients, and the 1- and 2-year local control rates were 79.1% (66.8-91.3%) and 64.1% (47.5-80.7%), respectively. Grade >= 3 lung toxicity was seen in six patients, esophageal toxicity occurred at grade <= 2, and there was no cardiac toxicity. Conclusion: The prognosis of patients with unresectable stage III NSCLC is poor without chemotherapy. Our data suggest that highdose PBT is beneficial and tolerable for these patients.