KLK3 and Epstein-Barr virus infection: While genetic factors, Epstein-Barr virus (EBV) infection and environmental factors are thought to be significant contributors to the development of nasopharynx cancer, more research is required to establish exact aetiological roles of early-onset nasopharynx cancer.20 Prostate-specific antigen (PSA) screening, which began in developed countries in the 1990s, contributed to the incidence of early-onset prostate cancer.20 However, it would be incorrect to solely attribute the entire increase in early-onset prostate cancer since 1986 to PSA screening.