Efficacy and limitations of delayed/salvage radiation therapy after radical prostatectomy

To assess the kinetics of prostate specific antigen (PSA) and the degree of PSA suppression, to better understand the efficacy and limitations of delayed/salvage radiation therapy after radical prostatectomy.

The PSA doubling time was calculated in patients with biochemical failure after radical prostatectomy and in those who underwent delayed/salvage radiation therapy. Patients in whom PSA was undetectable by conventional assay after irradiation were followed using a hypersensitive PSA assay.

Of 125 patients who underwent radical prostatectomy for clinically resectable prostate cancer, 47 developed biochemical failure at a mean of 11.8 months after surgery; 38 of these patients underwent radiotherapy (36 for isolated biochemical failure and two for local progression with elevated PSA levels). The mean (sd) PSA doubling time after surgery was 14.6 (16.2) months (n=44) and after radiation therapy it was 13.3 (23.9) months (n=32). Eleven of 30 evaluable patients (37%) had a sustained PSA suppression lasting at least 12 months after radiotherapy. Only the time to biochemical failure after surgery approached statistical significance for predicting a durable response to radiotherapy (P=0.08). The mean nadir value of PSA in the 11 patients with at least 12 months of sustained PSA suppression was 0.032 ng/mL at 26.9 months.

The rapidity with which PSA levels double after surgery may provide a clinically significant indication of the nature of these recurrent tumours, which deserve the best possible attempt at cure. Slow-growing tumours with longer PSA doubling times may be better candidates for delayed/salvage radiation therapy. Larger studies involving more patients are needed to determine whether the PSA doubling time can define subgroups for which specific treatment strategies should be developed.