KLK3 and lung cancer: In Japan, the incidence of prostate cancer increased from 30.4 per 100,000 in 2012 to 51.8 per 100,000 in 2020 and was even higher than that of lung cancer, with approximately 106,139 new cases in 2020.1,2 On the one hand, this increasing trend was related to the widespread use of prostate-specific antigen (PSA) screening as prostate cancer diagnosis.3 However, it is worth noting that population-based PSA screening was not recommended in recent years because of the problem of overdiagnosis.4