Early PSA level decline is an independent predictor of biochemical and clinical control for salvage postprostatectomy radiotherapy.

BACKGROUND

To improve the early detection of responders to salvage external beam radiotherapy (RT) after radical prostatectomy (RP).

METHODS

Between 2002 and 2007, in a single institution, 136 consecutive patients received salvage RT to a dose of 66 Gy without androgen-deprivation therapy after RP for a rising prostate-specific antigen (PSA) level. PSA measurements were systematically performed before RT (PSART), at the fifth week of RT (PSA5), and in the follow-up at least twice a year (every 6 mo). The PSA level decline during RT was expressed as PSA ratio (PSA5/PSART). Two different definitions of biochemical failure after salvage RT were considered: PSA level>0.4 ng/ml and PSA>PSA nadir post-RT +0.4 ng/ml. Statistical analyses included univariate and multivariate Cox regression models.

RESULTS

The median follow-up was 60 months. The 5-year freedom from biochemical and clinical failure rates were 57% (95% CI: 48%-66%) and 92% (95% CI: 87%-97%), respectively. The mean PSA5 was 0.61 ng/ml (range: 0-7) and the mean PSA ratio was 0.67 (0-1.7). A PSA ratio<1 was a significant prognostic factor in multivariate analysis for both definitions of biochemical failure (P = 0.01 for both) and for clinical failure (P = 0.005).

CONCLUSIONS

For patients undergoing salvage RT after RP for a rising PSA level, the absence of PSA level decline during RT is predictive of biochemical and clinical failure and may be used to rapidly identify poor responders.