Based on recent recommendations from the PCWG, PSA responses to drug treatment that affect tumor cell kill can be categorized into three distinct patterns: 1) significant and sustained PSA decline after drug treatment for “responders”, 2) initial decline followed by a slow PSA increase for “partial responders”, and 3) a transient decrease followed by a rapid PSA increase observed in “non-responders” [49]. The gene discussed is KLK3; the disease is neoplasm.