Continuous prostate-specific antigen rise despite salvage radiotherapy following radical prostatectomy: Pattern of clinical relapse and predictive factors.

Salvage radiotherapy for post-prostatectomy biochemical recurrence does not always control the disease. It would be useful to identify patients who would not benefit from radiotherapy to the prostate bed prior to making treatment recommendations. One such group of patients is those who experience continuously rising prostate-specific antigen (PSA) despite radiotherapy. The purpose of this study was to identify risk factors for continuous PSA increase and the pattern of radiological relapse during follow-up. We performed a retrospective comparison of two patient groups with PSA decline or continuous increase following salvage radiotherapy to the prostate bed. All patients received 3-D conformal radiotherapy (35 fractions of 2 Gy). Patients with continuous PSA increase were more likely to have had complete surgical resection (negative margins) and a shorter interval to radiotherapy (<24 months). However, the only statistically significant risk factor was Gleason score. Sixty-four percent of patients with a Gleason score of 9 developed continuously increasing PSA, indicating that residual subclinical cancer was not located in the prostate bed. The median time to radiological recurrence was 43 months. Isolated pelvic nodal recurrence was uncommon. Almost all patients with radiological recurrence had high-risk disease, in particular stage pT3. In conclusion, the majority of patients with biologically aggressive tumors with Gleason score 9 were not adequately treated with prostate bed radiotherapy alone. The predominant pattern of radiological recurrence was outside of the pelvis. Therefore, the problem of distant micrometastases has to be addressed.