Purpose: To evaluate retrospectively the safety and efficacy of high-dose proton beam therapy (PBT) for Stage I non-small-cell lung cancer (NSCLC).
Methods and materials: Between 1999 and 2003, 37 patients were treated in our institution. The indications for PBT were pathologically proven NSCLC, clinical Stage I, tumor size < or =5 cm, medically inoperable or refusal of surgery, and written informed consent. A total dose of 70-94 Gy(E) was delivered in 20 fractions (3.5-4.9 Gy(E) per fraction).
Results: Patient characteristics (number of patients) were as follows: Stage IA/IB, 17 of 20; medically inoperable/refusal of surgery, 23/14; total dose 70/80/88/94 Gy(E), 3/17/16/1. With a median follow-up period of 24 months, the 2-year local progression-free and overall survival rates were 80% and 84%, respectively. The 2-year locoregional relapse-free survival rates in Stage IA and Stage IB were 79% and 60%, respectively. No serious acute toxicity was observed. Late Grades 2 and 3 pulmonary toxicities were observed in 3 patients each. Of these 6 patients, 5 had Stage IB disease.
Conclusions: Proton beam therapy is a promising treatment modality for Stage I NSCLC, though locoregional relapse and late pulmonary toxicities in Stage IB patients were substantial. Further investigation of PBT for Stage I NSCLC is warranted.