Cost-effectiveness analysis of intensity modulated radiation therapy versus robot-assisted radical prostatectomy for patients with low-risk prostate cancer in Japan

This study evaluated the cost-effectiveness of hypofractionated intensity-modulated radiation therapy delivered in 20 fractions (IMRT-20) compared with robot-assisted radical prostatectomy (RARP) for patients with localized low-risk prostate cancer in Japan. A state-transition Markov model was developed from the Japanese healthcare system, using Japanese-specific cost data. Clinical probabilities, adverse event rates and health utility values were primarily derived from international sources, including the ProtecT trial, with extensive sensitivity and scenario analyses to address parameter uncertainty. The base-case analysis compared IMRT-20 and RARP. Scenario analyses included conventional fractionated IMRT (IMRT-38) versus RARP, as well as IMRT-20 versus RARP excluding the utility decrement associated with sexual dysfunction to explore preference-sensitive outcomes. Model outputs included quality-adjusted life-years (QALYs), incremental cost-effectiveness ratios (ICERs) and incremental net monetary benefit (INMB). In the base-case analysis, IMRT-20 yielded a modest QALY gain (0.1164) at slightly higher costs compared with RARP, resulting in an ICER of JPY 143 685 per QALY, well below the Japanese willingness-to-pay threshold of JPY 5 000 000 per QALY. Probabilistic sensitivity analysis showed that IMRT-20 was cost effective in 78.1% of simulations. IMRT-38 was less cost effective because of longer treatment duration and higher resource utilization (ICER JPY 3 317 380 per QALY), although it remained below the threshold. When the disutility of sexual dysfunction was excluded, IMRT-20 was dominated by RARP; however, INMB analysis indicated that IMRT-20 became economically favorable when the disutility exceeded 20%. Overall, IMRT-20 represents a clinically and economically efficient definitive treatment strategy for localized low-risk prostate cancer in Japan, supporting value-based cancer care.