Salvage radiotherapy after prostatectomy - what is the best time to treat?

PURPOSE Salvage radiotherapy (SRT) is applied routinely in patients with biochemical relapse after radical prostatectomy (RP). However, only ∼30% of these patients achieve a durable response after 10 years. As a standard, 66 Gy are given, ideally with a PSA below 0.5 ng/ml. We tried to determine more precisely the optimal PSA for starting SRT. MATERIAL AND METHODS In 301 prostate cancer patients without hormonal treatment, we analysed the impact on the biochemical response (bNED) to SRT of two pre-SRT PSA levels, namely below or above the median of 0.28 ng/ml. RESULTS The median follow-up time for the entire group was 30 months. In 151 patients, SRT commenced at a PSA ≤ 0.28 ng/ml, in 150 at > 0.28 ng/ml. Eighty-two patients (27%) developed biochemical progression during follow up. The calculated two-year bNED was 74% for the entire group, 78% versus 61% for a PSA ≤ or > 0.28 ng/ml, respectively. In multivariate analysis, pT(3b), resection status, pre-SRT PSA dichotomized at median, PSA post-SRT undetectable, and PSA doubling time were statistically significant independent predictors of progression after SRT. CONCLUSIONS Our findings suggest that a PSA of ≤ 0.28 ng/ml improves bNED compared with a PSA before SRT of > 0.28 ng/ml.