Published by the NCC group, Korea, this study reported clinical outcomes and dosimetry comparison of 289 patients with stage I NSCLC treated with protons (n=112) and photons (n=177). The median total radiation dose was 60 (range, 48–70) Gy, fraction 4 (range, 4–22). With a median follow-up duration of 27 months, the 2-year local PFS and OS rates were 94.0% and 83.0%, respectively. BED ≥125 Gy was significantly associated with improved PFS and OS. Propensity score matching created two groups of 93 patients, who each underwent photon or proton RT, showed that the local PFS and OS did not differ between these two groups. However, PBT showed significantly lower lung and heart radiation exposure in the mean dose, V5, and V10 than photon radiotherapy. The authors suggested that proton therapy could be an effective treatment to reduce long-term toxicities of the lung and heart.