This study from Japan estimated the incremental cost-effectiveness ratio (ICER) of PBT as a replacement for three-dimensional conformal RT (3DCRT). The effectiveness of PBT and 3DCRT was 1.67610615 and 0.97181271 QALY, respectively. The ICER was estimated to be ¥5,376,915 (US$46,756) per QALY. With the threshold for anti-cancer therapy by the Japanese authority of ¥7,500,000 (US$65,217) per QALY gain, PBT replacing 3DCRT is cost-effective and justifiable as an efficient use of finite healthcare resources.