External Beam Radiation and Brachytherapy for Prostate Cancer: Worthwhile Long-Term Outcomes

Long recognized as standard treatment of gynecologic cancer and someother malignancies, brachytherapy may also play a role in the treatmentof prostate cancer, said Dr. John C. Blasko of the University of Washingtonin Seattle.

A group of 231 consecutive patients with prostate cancer were treatedand followed prospectively with prostate-specific antigen (PSA), biopsyand clinical outcome between 1987 and 1994. The average age of patientswas 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 T3disease. The remaining 30% had T1C-T2A disease. Prior to biopsy, 17% ofpatients presented with a normal PSA level of between 0 and 4 ng/mL, and21% of patients had an initial PSA level of higher than 20 ng/mL. MeanPSA was 15.6.

Initially, patients were treated with external beam radiation; subsequently,2 to 4 weeks later, a permanent brachytherapy implant boost (with eitheriodine-125 or palladium-103) was employed on an outpatient basis. Although125 patients with well-differentiated tumors were treated with iodine-125and 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 factorfor biochemical failure. Patients with well-differentiated tumors did best.Cause-specific survival was 96%, disease-free survival was 74%, and overallsurvival was 70% at 8 years.

When the morbidity associated with a permanent-source brachytherapyboost was compared with that of conventional external beam radiation, rectalcomplications appeared to be the same. Also, for patients who did not undergotransurethral resection of the prostate, there was no increase in genitourinarycomplications (including incontinence) in the group that underwent brachytherapy.However, an unacceptable increase in incontinence was noted in patientswho underwent brachytherapy after transurethral resection of the prostate.For such patients, lowering the urethral dose by peripheral source distributionis 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 thisgroup of patients with moderately advanced disease, the results using brachytherapyare superior to those in patients treated with external beam radiation.