Association of [-2]proPSA with biopsy reclassification during active surveillance for prostate cancer

Previous studies have suggested an association between [-2]proPSA expression and prostate cancer detection. Less is known about the usefulness of this marker in following patients with prostate cancer on active surveillance. Thus, we examined the relationship between [-2]proPSA and biopsy results in men enrolled in an active surveillance program.

In 167 men from our institutional active surveillance program we used Cox proportional hazards models to examine the relationship between [-2]proPSA and annual surveillance biopsy results. The outcome of interest was biopsy reclassification (Gleason score 7 or greater, more than 2 positive biopsy cores or more than 50% involvement of any core with cancer). We also examined the association of biopsy results with total prostate specific antigen, %fPSA, [-2]proPSA/%fPSA and the Beckman Coulter Prostate Health Index phi ([-2]proPSA/free prostate specific antigen) × (total prostate specific antigen)(½)).

While on active surveillance (median time from diagnosis 4.3 years), 63 (37.7%) men demonstrated biopsy reclassification based on the previously mentioned criteria, including 28 (16.7%) of whom had reclassification based on Gleason score upgrading (Gleason score 7 or greater). Baseline and longitudinal %fPSA, %[-2]proPSA, [-2]proPSA/%fPSA and phi measurements were significantly associated with biopsy reclassification, and %[-2]proPSA and phi provided the greatest predictive accuracy for high grade cancer.

In men on active surveillance, measures based on [-2]proPSA such as phi appear to provide improved prediction of biopsy reclassification during followup. Additional validation is warranted to determine whether clinically useful thresholds can be defined, and to better characterize the role of %[-2]proPSA and phi in conjunction with other markers in monitoring patients enrolled in active surveillance.