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Seeds, External Beam RT Equally Effective in Early-Stage Disease

Seeds, External Beam RT Equally Effective in Early-Stage Disease

PHOENIX—For many men with early-stage prostate cancer, the choice between external beam radiotherapy and brachytherapy (seed implantation) can be made based solely on lifestyle issues and personal preference, according to results of a study reported at the 40th Annual Meeting of the American Society for Therapeutic Radiology and Oncology.

A review of 2,222 men with prostate cancer in the Phoenix metropolitan area showed that both methods of delivering radiotherapy are equally efficacious, in terms of survival, for most patients with stage T1/T2 disease.

“The purpose of this study was to define the outcome for these early-stage patients with either external beam alone or brachytherapy alone, and to further define the indications for either treatment,” said David G. Brachman, MD, of Arizona Oncology Services, a multiphysician radiation oncology practice in the Phoenix metropolitan area.

Patients were not randomized, Dr Brachman said, but received treatment based upon the preference of the patient or of the treating or referring physician. A total of 695 patients received implants and 1,527 underwent external beam radiation. The median age in both groups was 74 years. Median follow-up was 51 months for the brachytherapy group and 41 months for patients who had received external beam radiotherapy.

Patients who had previously received or were concurrently treated with hormones were excluded, as were men who had received both external beam radiotherapy and seed implantation.

The majority of men had T2 lesions, including 83% of those with seed implants and 81% who underwent external beam therapy. Of the brachytherapy patients, 31% had PSA levels greater than 10 ng/mL, as did 54% of the external beam patients. The treatment groups were well balanced for Gleason scores.

Survival Results Similar

Final analysis showed that overall survival for both treatment groups was remarkably similar. “If you compare just external beam vs brachytherapy with the Kaplan-Meier curves,” Dr. Brachman said, “they are virtually indistinguishable.” Of the brachy-therapy patients, 75% were failure free at 5 years, as were 69% of men who received external beam radiotherapy. The difference was not statistically significant.

Dr. Brachman also noted that no significant differences were observed when the groups were analyzed according to stage. “The failure-free survival rates at 5 years for T1s were 83% for brachytherapy and 78% for external beam therapy,” he reported, “and 67% for both treatments in the T2 categories.”

PSA, Gleason Scores Predictive

Failure-free survival was influenced to a certain degree by Gleason scores and PSA levels, Dr. Brachman said. Patients with Gleason scores ranging from 2 to 7 experienced equivalent outcomes in this study, but for those with Gleason 8 to 10, failure-free survival did differ by treatment, with 52% of the external beam patients failure free at 5 years but only 28% of the brachytherapy patients. The difference in favor of external beam radiotherapy for men with Gleason scores of 8 or more was significant at P = .04.

Dr. Brachman noted that “things get a little more interesting” when one looks at PSA levels. Survival rates for men whose PSA levels ranged from 0 to 10 ng/mL or were greater than 20 ng/mL were identical for both types of radiotherapy. A difference in survival was observed, however, in men whose PSA levels ranged from 10 to 20 ng/mL. At 5 years, survival was 70% for external beam patients and 53% for those with seed implants.

For the majority of early-stage prostate cancer patients in Dr. Brachman’s sample, failure-free survival was the same with either brachytherapy or external beam radiotherapy. Thus, he said, patients with a Gleason score of 7 or less and PSA level of 10 ng/mL or less can safely choose either treatment.

However, patients with PSA concentration between 10 and 20 ng/mL or a Gleason score of 8 to 10 “are probably better off with external beam,” Dr. Brachman advised.

Patients with PSAs greater than 20 ng/mL fare equally poorly with either treatment, he said, “and even with a low Gleason score, and by that we mean 2 to 4, we no longer use seed implants alone if the PSA concentration is greater than 10 to 20 ng/mL.”

Dr. Brachman pointed out that this large-scale investigation was unique in that it compared brachytherapy and external beam radiotherapy as employed by a single, community-based practice. “When we compared our results to those of other centers of urologic excellence, we didn’t do too badly. We think that the radiotherapy community ought to be happy with that because this was a community-based outcomes study.”

 
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