Hypofractionated Proton Beam Radiotherapy for Stage I Lung Cancer

Abstract

To determine the efficacy and toxicity of high-dose hypofractionated proton beam radiotherapy for patients with clinical stage I lung cancer. A prospective phase 2 clinical trial. Loma Linda University Medical Center. Subjects with clinical stage I non-small cell lung cancer who were medically inoperable or refused surgery. All patients were treated with proton beam radiotherapy. The target included the gross tumor volume as seen on CT scan, with additional margin to allow for respiratory motion. A multibeam treatment plan was generated. Delivered treatment was 51 cobalt Gray equivalent (CGE) in 10 fractions over 2 weeks to the initial 22 patients; the subsequent 46 patients received 60 CGE in 10 fractions over 2 weeks. Sixty-eight patients were analyzed for this report, with a median follow-up time of 30 months. No cases of symptomatic radiation pneumonitis or late esophageal or cardiac toxicity were seen. The 3-year local control and disease-specific survival rates were 74%, and 72%, respectively. There was significant improvement in local tumor control in T1 vs T2 tumors (87% vs 49%), with a trend toward improved survival. Cox regression analysis revealed that patients with higher performance status, female gender, and smaller tumor sizes had significantly improved survival. High-dose hypofractionated proton beam radiotherapy can be administered safely, with minimal toxicity, to patients with stage I lung cancer. Local tumor control appears to be improved when compared to historical results utilizing conventional radiotherapy, with a good expectation of disease-specific survival 3 years following treatment.