Dose escalation for patients with decreasing PSA during radiotherapy for elevated PSA after radical prostatectomy improves biochemical progression-free survival: results of a retrospective study.

Purpose: The optimal dose for salvage radiotherapy (SRT) after radical prostatectomy (RP) is still not defined. It should be at least 66 Gy. In the present study, the suitability of PSA regression as a selection criterion for an SRT dose escalation to 70.2 Gy was examined.
Patients and Methods: Between 1997 and 2007, 301 prostate cancer patients received SRT after RP at the Charité - University Medicine Berlin, Campus Benjamin Franklin. None of the patients had antihormone therapy prior to SRT. A total of 234 patients received 66.6 Gy. From 2002 on, 67 patients with a PSA decrease during SRT were irradiated with 70.2 Gy. The influence of this selection and dose escalation on freedom from biochemical progression (bNED) was analyzed.
Results: The median follow-up of the whole group was 30 months, the median pre-SRT PSA was 0.28 ng/ml. Of the patients, 27% (82/301) developed biochemical progression, 31% from the 66.6 Gy cohort (73/292) and 13% from the 70.2 Gy cohort (9/67) (p = 0.01). The calculated 2-years bNED was 74% for the whole group, 88% vs. 71% after 70.2 Gy and 66.6 Gy, respectively (p = 0.01). In a multivariate analysis, the total dose (p = 0.017), the re-achievement of an undetectable PSA after SRT (p = 0.005), and the infiltration of the seminal vesicles (p = 0.049) were independent parameters of bNED.
Conclusion: Our analysis suggests that patient selection during SRT for a dose escalation to 70.2 Gy can improve the freedom from biochemical progression in patients with SRT after RP.