In the early-stage NSCLC setting, all of the studies had a small sample size and were single-arm without direct comparison. Proton therapy was promising for locally advanced NSCLC with improved clinical outcomes and reduced toxicity when compared with historical photon therapy data, with lower rates of severe (grade 3) toxicities, although the only RCT reported grade ≥ 3 radiation pneumonitis rate of IMRT, 6.5% versus PSPT, 10.5%. Further study of PBS is ongoing and direct comparison is warranted.