Interstitial iodine-125 radiation without adjuvant therapy in the treatment of clinically localized prostate carcinoma.

Abstract

This study was designed to evaluate the efficacy of iodine-125 interstitial radiation in the treatment of prostate carcinoma classified as T1 or T2. One hundred twenty-six consecutive patients with adenocarcinoma of the prostate (T1, 23%; T2, 77%) were treated with iodine-125 radionuclides between January 1, 1988, and December 31, 1990. Four patients died of intercurrent illness within 1 year postimplant, leaving 122 men in the study. The prescribed minimum radiation dose was 160 gray. Median follow-up was 69.3 months. Prebiopsy prostate specific antigen (PSA) values (median, 5.0 ng/mL) were available for all patients. Posttherapy evaluation included clinical, biochemical (PSA), and pathologic (repeat needle biopsy) studies. No patient was surgically staged, and none received androgen deprivation therapy. Morbidity was graded according to the Radiation Therapy Oncology Group grading scale. Statistical appraisal was performed by the Kaplan-Meier method. PSA failure was defined in two ways: (1) PSA progression, i.e., 2 consecutive increases from a nadir value; and (2) failure to attain an arbitrary serum PSA value of 1.0 or 0.5 ng/mL at last follow-up. The overall 7-year survival was 77%; there were no deaths from prostate carcinoma in this cohort. The 7-year actuarial PSA progression free outcome was 89%, and the PSA < or = 1.0 ng/mL outcome was 87%. When PSA < or = 0.5 ng/mL was selected as an outcome end point, and PSA values in this series of radiation-treated patients were compared with PSA values proposed to indicate disease free survival after radical prostatectomy (PSA < or = 0.3-< or = 0.6 ng/mL), the 7-year actuarial disease free survival was 79%. Morbidity was minimal except in patients who had preimplant or postimplant transurethral prostate resection. Outpatient-based iodine-125 prostate brachytherapy for prostate carcinoma classified as T1 or T2 resulted in biochemical outcomes comparable to end points resulting from radical prostatectomy and external beam radiation.