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

Abstract

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. 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). 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% (25.3-53.5%), 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. The prognosis of patients with unresectable stage III NSCLC is poor without chemotherapy. Our data suggest that high-dose PBT is beneficial and tolerable for these patients.