KLK3 and cancer: The original hypothesis proposed by Oesterling was that age-specific reference ranges for serum PSA would potentially detect earlier organ-confined prostate cancer in younger men at a time when the tumours are potentially more susceptible to cure (increased sensitivity), while at the same time detect less cancers in older men who might have clinically insignificant tumours or have a less than 10-year life expectancy (increased specificity).