High dose proton beam therapy (PBT) for stage I non-small cell lung cancer (NSCLC)

Abstract

7226 Background: Proton beam has a distinctive depth-dose curve that enables us to deliver higher doses to the tumor without increasing doses to the surrounding normal tissues. We retrospectively evaluated the safety and efficacy of high dose PBT in patients with stage I NSCLC. Methods: Between December 1999 and December 2003, 37 patients with stage I NSCLC were treated by PBT in our institution. The indication of PBT were 1) clinical stage I NSCLC, 2) PaO2 ≥ 60 torr, 3) medically inoperable, or refusal of surgery, 4) performance status 0–2, 5) written informed consent. The target volume was defined as the gross tumor volume plus appropriate margins for subclinical tumor extension, set-up error and respiratory motion. Treatment was performed using respiratory gating. A total dose of 70 - 94 GyE was delivered in 20 fractions over 4 to 5 weeks. Kaplan-Meier method and CTC version 2.0 were used to assess survival and toxicity. Results: Patients characteristics were as follows: median age 75 years (range, 63 to 87); male/female, 30/7; Stage IA/IB, 17/20; squamous/ adenocarcinoma/ others, 15/15/7; medically inoperable/refusal of surgery, 23/14; total dose 70/80/88/94 GyE, 3/17/16/1. The response rate was 86% (95% confidence interval (CI), 71 to 96%). With a median follow-up period of 24 months (range, 3 to 57 months), the 2-year local progression-free and overall survivals were 94% (95%CI, 86 to 100%) and 82% (95% CI, 68 to 97%), respectively. No acute grade ≥ 2 toxicity was observed. Late grade 2 and grade 3 pulmonary toxicities were observed in 3 and 3 patients, respectively. The 2-year loco-regional progression-free survivals in stage IA and IB patients were 94% and 62%, respectively. Five of 6 patients who suffered late grade ≥ 2 pulmonary toxicity had stage IB disease. Conclusions: PBT is a promising treatment modality for stage I NSCLC, although loco-regional recurrences and late pulmonary toxicities in stage IB patients were substantial. Further investigation of PBT for stage I NSCLC is warranted. No significant financial relationships to disclose.