PSA bounce predicts early success in patients with permanent iodine-125 prostate implant

To determine the clinical and dosimetric factors that predict prostate-specific antigen (PSA) bounce after iodine-125 prostate brachytherapy and to determine the predictive value of PSA bounce relative to biochemical relapse-free survival (bRFS).

A multivariate analysis of factors thought to predict for PSA bounce was performed in 295 consecutive patients with T1-T2 prostate cancer treated by prostate brachytherapy as the sole radiotherapeutic modality and a minimum follow-up of 2 years. The variables examined included age, initial PSA level, biopsy Gleason score, use of androgen deprivation, occurrence of PSA bounce, dose received by 90% of the prostate gland, and volume of gland receiving 100% of the prescribed dose. A PSA bounce was defined as a rise of at least 0.2 ng/mL greater than a previous PSA level with a subsequent decline equal to, or less than, the initial nadir. A second analysis investigating the same factors and adding PSA bounce as a predictor of bRFS was also performed.

The median follow-up was 38 months. A PSA bounce was noted in 82 (28%) of 295 patients. On multivariate analysis, only younger age (younger than 65 years) significantly predicted for a PSA bounce. Patients who experienced a PSA bounce were less likely to have biochemical failure (P = 0.037). Overall, the bRFS rate at 5 years in those experiencing a PSA bounce was 100% versus 92% in those with no bounce.

Immediate salvage therapy in patients with a rising PSA level after permanent prostate brachytherapy should not be initiated provided the PSA increase does not exceed the pretreatment PSA value. A PSA bounce may be associated with improved bRFS but was not associated with any of the pretreatment clinical and dosimetric factors examined.