For men with intermediate risk prostate cancer, radiation treatment with brachytherapy alone can result in similar cancer control with fewer long-term side effects, according to research presented at the 58th Annual Meeting the American Society for Radiation Oncology (ASTRO).

The study is conducted at 68 cancer centers throughout the U.S. and Canada from 2003 to 2012 to assess whether brachytherapy conveyed an additional benefit or control of the cancer growth at five years following treatment.

Brachytherapy is a type of radiation therapy where radioactive seed implants are inserted directly into a patient’s tissue to deliver treatment to the tumor while limiting radiation exposure for surrounding tissue.

Participants in the study included 588 men diagnosed with intermediate risk prostate cancer and enrolled in the trial between 2003 and 2012.

Prostate cancer risk groups are assigned based on the prostate biopsy results and the prostate specific antigen (PSA) level in the patient’s blood at the time of diagnosis.

Patients were randomized to one of two treatment arms, where 292 patients received brachytherapy alone and 287 patients received external beam therapy in addition to brachytherapy (the EBT+B group).

Researchers compared the two treatment arms with two-sample binomial testing. Short-term/acute and long-term/late side effects also were measured.

At five years, survival rates for men who received brachytherapy alone were comparable to those who underwent more aggressive radiation treatment.

The rate at five years post-treatment was 85% for EBT+B patients and 86% for B patients.

Although rates were comparable between treatment groups, differences emerged in the rates of more serious side effects.

Overall toxicity levels were similar across groups only for acute side effects (i.e., those that occur closely following treatment), with eight percent of patients in each cohort reporting acute grade 3+ side effects.

Late severe toxicities were more common for EBT+B patients (12 percent) than for B patients (7 percent), as were severe GU side effects GU (7 vs. 3 percent) and severe GI toxicities (3 vs. 2 percent).

“These findings suggest that many men with intermediate risk prostate cancer can be well managed with seed implant alone and do not require the addition of external beam radiation,” said Bradley Prestidge, MD, lead author of the study.

“Contrary to expectations, the more aggressive, combined treatment did not result in superior cancer control rates at five years follow-up, indicating that men can achieve a similar survival benefit with fewer late side effects through brachytherapy alone.”