Proton Beam Therapy for Histologically or Clinically Diagnosed Stage I Non-small Cell Lung Cancer (NSCLC): The First Nationwide Retrospective Study in Japan

Abstract Purpose To investigate the efficacy and safety of proton beam therapy (PBT) for the treatment of Stage I non-small cell lung cancer (NSCLC). Methods and Materials Six hundred sixty-nine patients with 682 tumors with histologically or clinically diagnosed Stage I NSCLC according to the 7th edition of UICC who received passive-scattering PBT from April 2004 and December 2013 in Japan were retrospectively reviewed to analyze survivals, local control, and toxicities. Results Four hundred eighty-six (72.6%) of 669 patients were men, with the median age of 76 years (range, 42–94 years). NSCLC was histologically confirmed in 440 patients (65.7%). Clinical T stages included T1a (n = 265; 38.9%), T1b (n = 216; 31.7%), and T2a (n = 201; 29.4%). The total irradiation doses of PBT ranged from 74.4 to 131.3 biological effective dose (BED) GyE (median, 109.6 BED GyE). The median follow-up period was 38.2 months (range, 0.6–154.5 months) for all patients. The 3-year overall survival (OS) and progression-free survival (PFS) rates for all patients were 79.5% and 64.1%, respectively. For patients with Stage IA tumors, the 3-year OS and PFS rates were 82.8% and 70.6%, respectively, and the corresponding rates for patients with Stage IB tumors were 70.8% and 47.3%, respectively. The 3-year local progression-free rates for all, Stage IA, and Stage IB patients were 89.8%, 93.5%, and 79.4%, respectively. The incidence of Grade 2, 3, 4, and 5 pneumonitis was 9.8%, 1.0%, 0%, and 0.7%, respectively. The incidence of Grade ≥3 dermatitis was 0.4%. No Grade 4 or severe adverse events, other than pneumonitis, were observed. Conclusions PBT appears to yield acceptable survival rates, with a low rate of toxicities.