Clinical outcomes of proton beam therapy for inoperable stage I-IIA non-small cell lung cancer: Japanese nationwide registry study.

PURPOSE: Radiotherapy is the standard treatment for unresectable stage I-IIA non-small cell lung cancer (NSCLC). One treatment option within radiotherapy is proton beam therapy (PBT). Currently, a prospective observational study is being conducted at all proton therapy centers in Japan as part of a proton beam all-case registry. This study aimed to evaluate the outcomes of PBT for inoperable stage I-IIA NSCLC.

METHODS

We included patients with stage I-IIA (UICC 8th) NSCLC who had started PBT between May 2016 and June 2020. Overall survival (OS), progression-free survival (PFS), cumulative incidence of local failure (LF), and adverse events were evaluated. Prognostic factors were compared using log-rank test and Cox proportional hazards model. The cumulative incidence curves were compared using Gray's test.

RESULTS

A total of 309 patients were evaluated. The median follow-up period was 47 months, calculated using the reverse Kaplan-Meier method. The 3/5-year OS was 62.7 %/47.7 %, PFS was 52.9 %/40.0 %, and LF was 14.4 %/22.1 %. According to the stage, 3-year OS, PFS, and LF were 69.6 %, 58.7 %, 13.3 %, respectively, for stage IA; 55.3 %, 41.6 %, 15.6 %, respectively, for stage IB; 33.9 %, 41.5 %, 25.6 %, respectively, for stage IIA. Female sex and good performance status, absence of interstitial pneumonia, absence of double cancer, and T1 stage were favorable prognostic factors for OS in a multivariate analysis. Grade ≥ 4 adverse events were not observed.

CONCLUSION

This study provided real-world treatment outcomes of PBT for inoperable stage I-IIA NSCLC in Japan.