Consider Radiotherapy After Prostatectomy When PSA Is Undetectable

CHICAGO—Although radiotherapy has been administered after prostatectomy for decades to improve disease-free survival in men who have pathologic risk factors, its use in high-risk men who have undetectable PSA levels after prostatectomy is controversial.

Based on results of their study of adjuvant radiotherapy in men with positive surgical margins but PSA levels below 0.3 ng/mL, investigators from Baylor College of Medicine, Houston, believe that irradiation of the prostatic bed and periprostatic tissue should be considered after prostatectomy even if the PSA is not elevated.

The median disease-free interval for men receiving adjuvant radiotherapy was more than two times longer than it was for men who were observed after surgery. "Adjuvant radiotherapy can provide excellent long-term BNED [biochemical no evidence of disease] for men with positive surgical margins," said Michael D. Bastasch, MD, resident in radiation oncology in the Department of Radiology. He reported the results at the 87th Scientific Assembly and Annual Meeting of the Radiological Society of North America (abstract 34).

The researchers reviewed outcomes in 44 men who had been referred to their institution for treatment for prostate cancer between 1989 and 1995. All had undetectable PSA levels after surgery, negative lymph nodes, and no prior hormone therapy. All received adjuvant radiotherapy because of positive pathologic findings at the surgical margins.

Patients received radiotherapy over a period of 1.5 to 11 months after prostatectomy. Radiotherapy was delivered to the prostatic bed and surrounding prostatic tissues at a total median dose of 60 Gy (range, 59.4 to 66 Gy) given in fractions of 1.8 to 2.0 Gy.

Biochemical no evidence of disease (bNED) results in this group of patients were compared with findings from an observational group of 189 men from the same time period from the Specialized Program for Research Excellence (SPORE) database who had positive surgical margins and undetectable PSA levels after prostatectomy. Both groups were similar in terms of age, preoperative PSA, Gleason score, extracapsular extension, and seminal vesicle involvement.

The primary endpoint of the study was detection of PSA. The entire group was followed for a median of 60.4 months after surgery; the median follow-up in the adjuvant radiotherapy group was 89.8 months, and in the observational group, 59 months.

Four men (9%) in the adjuvant radiotherapy group failed treatment, as defined by an elevated PSA level, compared with 54 men (28.6%) in the observational group (P = .001). The difference in median disease-free interval between the two groups was highly statistically significant. The group receiving radiotherapy had an interval of 88.6 months vs 43.5 months for the observational group (P < .001).

A statistical analysis among all men in the study showed that extracapsular extension, a Gleason score of 7 to 10, and absence of radiotherapy were statistically significant risk factors for PSA failure.

The researchers concluded that "adjuvant radiotherapy should be considered for patients with high-risk pathologic factors after prostatectomy despite an undetectable PSA. Initiating postprostatectomy radiotherapy when the tumor burden is at a minimum may elicit the maximum benefits."