Brachytherapy alone causes less side-effects in mid-risk prostate cancer

30 Sep 2016

Brachytherapy, without external bream therapy, offers similar results against mid-risk prostate cancer, with fewer side effects.

This finding emerges from a study suggesting that brachytherapy alone can be used to manage patients with intermediate risk prostate cancer rather than the more conventional technique of combining brachytherapy with external beam therapy (EBT).

The results of the study were delivered at the annual meeting of the American Society for Radiation Oncology.
This study came out of NRG Oncology/RTOG 0232, a phase 3, multi-institutional trial conducted at 68 cancer centers throughout the U.S. and Canada from 2003 to 2012. That trial was designed to assess whether combining EBT with brachytherapy added benefit in terms of progression-free survival or control of cancer growth at 5 years following treatment.


The study: Brachytherapy and EBT

This study enrolled 588 men diagnosed with intermediate risk prostate cancer. To be eligible for the study patients had to have at least a Gleason 7 cancer score and a prostate-specific antigen (PSA) below 10, or alternatively, a patient could have a PSA as high as 20 with a Gleason score of 6 or lower. "So these men were not terribly high risk, but a more favorable intermediate risk," said Prestidge.

Patients were randomized into two treatment arms, with 292 receiving brachytherapy alone and 287 patients receiving 45 Gy (=unit of absorbed radiation) partial EBT to the pelvic area in addition to brachytherapy (EBT+B group).

For the study, EBT could be delivered either by intensity-modulated radiation therapy or 3D conformal radiation. Brachytherapy included radioactive iodine-125 or palladium-103, prescribed to 110 Gy or 100 GY for patients in the EBT+B group, and 145 Gy or 125 GY respective dose for patients in the brachytherapy-alone group.

Trial results

Prestidge and his colleagues determined that, at 5 years follow-up, survival rates for men in the brachytherapy group were comparable to those in the EBT+B group. The 5-year progression-free survival rate was 86% for the brachytherapy group compared to 85% for the EBT+B group.

Overall rates of side effects were similar across the groups only for acute side effects (those occurring closely after treatment), with 8% of patients in each group reporting acute grade 3+ toxicity.

However, the more aggressive therapy given to the EBT+B group resulted in more late severe effects for that group, with overall grade 3+ late toxicity rates of 12% for EBT+B compared to just 7% for brachytherapy. Grade 3 or higher genitourinary toxicity rates for the EBT+B and brachytherapy groups were 7% and 3%, respectively, while gastrointestinal toxicity rates were 3% and 2%, respectively.

Prestidge noted that, going into the study, he and his colleagues were working under the assumption that patients with intermediate risk prostate cancer who received the combination would have better outcomes by 10% (in terms of freedom from cancer progression at 5 years) compared to patients who had brachytherapy alone.

"What this means in terms of clinical practice is that men with intermediate risk prostate cancer may be quite well managed with brachytherapy alone," said Prestidge.

"Contrary to expectations, the more aggressive, combined treatment did not result in superior cancer control rates at 5 years follow-up, indicating that men can achieve a similar survival with fewer late side effects through brachytherapy alone," he said.

That represents "a bit of a paradigm shift," Prestidge noted, considering that the conventional treatment for intermediate risk prostate cancer has been the combination of EBT and brachytherapy.

He said that future work will include looking at subsets within the study cohort to compare more favorable to less favorable intermediate risk prostate cancer patients.


Source: MedPage Today

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