Long recognized as standard treatment of gynecologic cancer and some other malignancies, brachytherapy may also play a role in the treatment of prostate cancer, said Dr. John C. Blasko of the University of Washington in Seattle.
A group of 231 consecutive patients with prostate cancer were treated and followed prospectively with prostate-specific antigen (PSA), biopsy and clinical outcome between 1987 and 1994. The average age of patients was 69 years, and the mean follow-up was 62 months. Approximately 150 patients (65%) had stage T2B and higher disease and 11 patients (5%) had stage T3 disease. The remaining 30% had T1C-T2A disease. Prior to biopsy, 17% of patients presented with a normal PSA level of between 0 and 4 ng/mL, and 21% of patients had an initial PSA level of higher than 20 ng/mL. Mean PSA was 15.6.
Initially, patients were treated with external beam radiation; subsequently, 2 to 4 weeks later, a permanent brachytherapy implant boost (with either iodine-125 or palladium-103) was employed on an outpatient basis. Although 125 patients with well-differentiated tumors were treated with iodine-125 and 120 patients with high-grade lesions were treated with palladium-103, no difference in outcome was detected between the two groups.
In this series, histologic grade seemed to be the most significant factor for biochemical failure. Patients with well-differentiated tumors did best. Cause-specific survival was 96%, disease-free survival was 74%, and overall survival was 70% at 8 years.
When the morbidity associated with a permanent-source brachytherapy boost was compared with that of conventional external beam radiation, rectal complications appeared to be the same. Also, for patients who did not undergo transurethral resection of the prostate, there was no increase in genitourinary complications (including incontinence) in the group that underwent brachytherapy. However, an unacceptable increase in incontinence was noted in patients who underwent brachytherapy after transurethral resection of the prostate. For such patients, lowering the urethral dose by peripheral source distribution is necessary, although a definite safe dose has not yet been established.
The 8 year PSA less than 1.0 control rate was 65% at 8 years. Thus, the importance of this trial, according to Dr. Blasko, is that, in this group of patients with moderately advanced disease, the results using brachytherapy are superior to those in patients treated with external beam radiation.