KLK3 and pachyonychia congenita: Some of PSA metrics (e.g., PSA velocity greater than 1.5 ng/ml/yr and PSA doubling time <6 months) are surrogate for PC mortality or overall survival (OS) (D’Amico et al., 2003) but others (e.g., PSA decline ≥30% and PSA doubling time >12 months) are not surrogate endpoint (Collette, Buyse & Burzykowski, 2007; Halabi et al., 2013; Valicenti et al., 2006).