Zhang L et al. (2006) Modeling prostate specific antigen kinetics in patients on active surveillance. J Urol 176: 1392–1398

The majority of diagnosed prostate cancers will never progress to the point of needing treatment. Physicians face the challenge of identifying which patients will progress and require active treatment, and which patients can be safely managed by observation alone. Zhang et al. have now proposed guidelines based on the results of their new, prospective, cohort study.

Between 1995 and 2005, 231 men with prostate cancer at low risk of progression (stage T1b–T2b N0M0 disease, Gleason score ≤7, and PSA level <15 ng/ml) were managed with observation. Over the course of the study, 93 patients were reclassified as being at high risk of disease progression and were given appropriate active treatment; data from after reclassification was not included in the analysis. Before any active treatment was given, Zhang et al. used a computer model to predict the evolution of serial PSA levels, which were later compared with actual group and individual PSA doubling times.

Two average prediction lines were produced—one for the high-risk group and one for the low-risk group. The actual average PSA doubling time was 2.97 years in the high-risk group and 6.54 years in the low-risk group. Zhang et al. suggest that active treatment should be initiated if >40% of the patient's measurements lie above the predicted high-risk line, and that observation can be relaxed if >35% of the patient's measurements lie below the predicted low-risk line.