Prostate-specific antigen (PSA) kinetics in untreated, localized prostate cancer: PSA velocity vs PSA doubling time

To compare the accuracy of prostate-specific antigen (PSA) velocity (PSAV) vs PSA doubling time (DT) for predicting the repeat biopsy results in men with localized prostate cancer on active surveillance (AS), as the utility of PSAV vs PSADT in untreated prostate cancer has not been well studied. Eligible patients had favourable-risk localized prostate cancer (T1/2a, PSA level <= 15 ng/mL, Gleason score <= 3 + 4, and percentage positive biopsy cores <= 50%), and consented to AS between 2002 and 2005. Repeat biopsies were taken after 18-24 months, with adverse histology defined as any of: primary Gleason grade >= 4, > 50% cores positive, or initial Gleason score 3 + 3 upgraded to >= 3 + 4. Using all PSA values for the 2 years preceding repeat biopsy, the PSAV and PSADT were calculated using linear regression and the log-slope method (DT = ln2/slope), respectively. In all, 199 patients were assessable; the median PSAV and PSADT were 0.71 ng/mL/year and 5.29 years, respectively. Fifty-three patients (27%) had adverse histology on repeat biopsy. On univariate analyses, PSAV (P < 0.001) and PSADT (P = 0.019) were associated with adverse histology. The area under the receiver operating characteristic curve for predicting adverse histology was 0.70 and 0.63 for PSAV and PSADT, respectively. The mean difference was 0.07 (95% confidence interval 0.03-0.12; P < 0.001). PSAV is more accurate than PSADT for predicting adverse histology on repeat biopsies. These data suggest that PSAV should be used in preference to PSADT to describe PSA kinetics in untreated, localized prostate cancer.