NEW ORLEANSIn the treatment of localized prostate cancer, biochemical failure rates are similar among permanent radioactive seed implantation, high-dose external beam radiation therapy, combination seeds/external radiation, and radical prostatectomy, according to a very large series of patients followed at the Cleveland Clinic Foundation and Memorial Sloan-Kettering Cancer Center.
Patrick A. Kupelian, MD, who is currently at M.D. Anderson Medical Center Orlando, an affiliate of the Houston center, reported the results at the American Society for Therapeutic Radiology and Oncology meeting (ASTRO abstract 61).
The study reviewed the biochemical- relapse-free survival rates after each treatment modality in 2,991 patients with stage T1-T2 localized prostate cancer who had available pretreatment PSA levels and biopsy Gleason scores. The patients were treated between 1990 and 1998, and followed for a minimum of 1 year, with median follow-up of almost 5 years.
Treatment was as follows: radical prostatectomy in 1,034 (35%); external beam radiation therapy less than 72 Gy in 484 (16%) (median dose, 68.4 Gy); external beam radiation therapy 72 Gy or higher in 301 (10%) (median dose, 78 Gy); seed implantation in 950 (32%); and combined seeds and external radiation in 222 (7%). Biochemical relapse was defined as PSA level greater than 0.2 ng/mL for radical prostatectomy cases and as three consecutive rising PSA levels for all others.
For all patients, the biochemical-relapse-free survival was 76% at 5 years and 72% at 7 years. The outcomes for external beam radiotherapy less than 72 Gy were significantly worse than for the other four modalities (P < .001) (see Table). "For all but low-dose external beam, all the curves essentially overlapped at around 75% to 83%," Dr. Kupelian said.
In the multivariate analysis, treatment modality was a significant predictor of outcome in all cases, he said, "but if we drop patients who received less than 72 Gy radiation, there are no significant differences in outcomes according to treatment. I think we can clearly say that outcomes are significantly worse for low-dose external beam radiation."
When external beam radiation less than 72 Gy was excluded from the multivariate analysis, independent predictors of relapse included initial PSA, Gleason score, and year of therapy, he said.