The value of PSA measurements at 30 Gy, 50 Gy and 60 Gy for dose limitation in patients with radiotherapy for PSA increase after radical prostatectomy.

Abstract

Radiation therapy is a treatment option for patients with rising PSA after radical prostatectomy without histological evidence of local relapse and no signs of distant metastases. Prior to radiotherapy there is no certainty whether a patient is going to respond to the treatment or not. When total doses of more than 60 Gy are given there is an exponential rise in treatment-related late toxicity. Therefore those patients in whom radiotherapy later appears to be ineffective may benefit from a dose restriction to 50-60 Gy. The aim of this study was to examine the prognostic value of PSA levels evaluated during radiotherapy. 41 patients with rising PSA level following prostatectomy received radiotherapy to the prostatic bed and were treated up to a median dose of 66.6 Gy. We evaluated serum PSA levels during radiotherapy at 30 Gy, 50 Gy, and 60 Gy and compared them to the pre-radiotherapy PSA level and the outcome of radiotherapy. After radiotherapy, 31 patients (76%) had either undetectable (n = 15), or decreasing but still detectable PSA levels (n = 16) and ten patients (24%) had rising PSA levels and did not respond. PSA evaluation at 30 Gy showed that 26% (8/31) of those patients who would respond to radiotherapy still had a rising PSA when compared to pretreatment PSA. At 50 Gy and 60 Gy 93% (27/29) of these patients had decreasing PSA levels. In contrast, 75% (6/8) and 88% (7/8) of those patients in whom radiotherapy was not effective had rising PSA levels at 50 Gy and 60 Gy (p < 0.05). PSA measurements at 30 Gy, 50 Gy and 60 Gy for radiotherapy of PSA increase following radical prostatectomy without histologically proven local recurrence gives valuable information about the later tumor response. Therefore it possibly gives the opportunity to finish radiotherapy between 50 and 60 Gy, as almost all patients with continued PSA increase at 60 Gy do not stand to profit from radiotherapy. In these patients dose limitation would significantly decrease the risk of late side effects, especially for the bladder and the rectum. PSA evaluations at 30 Gy and 50 Gy or 60 Gy are recommendable.