Effect of early salvage radiotherapy at PSA < 0.5 ng/ml and impact of post-SRT PSA nadir in post-prostatectomy recurrent prostate cancer.

BACKGROUND

For patients with recurrent prostate cancer after radical prostatectomy (RP), salvage radiotherapy (SRT) offers a second chance of cure. European guidelines (EAU) recommend SRT at a PSA < 0.5 ng/ml. We analyze the efficacy of SRT given according to this recommendation and investigate the predictive power of the post-SRT PSA nadir.

METHODS

Between 1998 and 2013, 301 patients of two university hospitals received SRT at a PSA < 0.5 ng/ml (median 0.192 ng/ml, IQR 0.110-0.300). Patients, who previously received androgen deprivation therapy, were excluded. All patients had 3D-conformal RT or intensity-modulated radiotherapy (IMRT, n = 59) (median 66.6 Gy). The median follow-up was 5.9 years. Progression and overall survival were the endpoints.

RESULTS

After SRT, 252 patients re-achieved an undetectable PSA. In univariate analysis, pre-RP PSA ≥ 10 ng/ml, pT3-4, Gleason score (GS) 7-10 or 8-10, negative surgical margins, post-RP PSA ≥ 0.1 ng/ml, pre-SRT PSA ≥ 0.2 ng/ml and post-SRT PSA nadir ≥ 0.1 ng/ml correlated unfavorably with post-SRT progression. In a multivariable Cox model, pT3-4, GS 7-10, negative margins and a pre-SRT PSA ≥ 0.2 ng/ml were significant risk factors. If the post-SRT PSA was added to the analysis, it dominated the outcome (HR = 9.00). Of the patients with a pre-SRT PSA < 0.2 ng/ml, only 9% failed re-achieving an undetectable PSA. Overall survival in these patients was 98% after 5.9 years compared to 91% in patients with higher pre-SRT PSA (Logrank p = 0.004).

CONCLUSIONS

SRT at a PSA < 0.2 ng/ml correlates significantly with achieving a post-SRT undetectable PSA (<0.1 ng/ml) and subsequently with improved freedom from progression. Given these overall favorable outcomes, whether additional androgen deprivation therapy is required for these men requires further study.