Where it has been used, the data may be conflicting as they are for prostate-specific antigen velocity in prostate cancer2–4 or limited as they are for ovarian cancer.1,5,6 Modeling studies5,6 that use data from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial7 suggest that up to a third of the ovarian cancer cases could have been detected earlier if cancer antigen 125 (CA-125) velocity had been used instead of a fixed cutoff. The gene discussed is KLK3; the disease is ovarian carcinoma.