High Doses of Radiation Found to be Effective, With Few Side Effects

"This is the first study that is looking at 10-year results of dose escalation with 3D-CRT and demonstrating improved outcomes in all subgroups of patients treated with high doses of radiation compared to lower conventional dose levels," said the study's lead author Michael Zelefsky, MD, Chief of MSKCC's Brachytherapy Service. "We observed that the radiation dose was one of the critical ingredients, or predictors, for achieving improved outcome and enhanced disease control rates in each of the patient groups we evaluated."

Researchers analyzed data from 828 MSKCC patients treated between 1988 and 1997. The patients were categorized into prognostic risk groups based on pre-treatment PSA levels, Gleason score, and clinical stage. At 10 years, the PRFS outcomes for favorable, intermediate, and unfavorable risk patients were 70 percent, 49 percent, and 35 percent respectively. Higher radiation dose levels (the doses in the study ranged from 64.8 Gy up to 75.6 Gy) were associated with an improved PRFS at 10 years for each prognostic group.

The other significant finding of the study is that patients had minimal side effects, despite the fact that higher doses of radiation were delivered. The long-term risk of serious rectal or bladder injuries at 10 years was 2 ½ percent and 1 ½ percent, respectively. "This dispels the notion that as time goes on the side effects become more noticeable and patients are more at risk for developing long-term damage years out from treatment," said Dr. Zelefsky.

"Radiation dose has a significant impact on the outcome of patients with localized prostate cancer treated with radiation therapy. We continue to observe that even higher doses have further improved cure rates for patients with localized prostate cancer," said Steven Leibel, MD, Chairman of MSKCC's Department of Radiation Oncology and the study's senior author. "These mature data show that even 10 years from the therapy, despite the application of high radiation doses, the tolerance was excellent."