High-dose radiotherapy doesn’t improve survival in men with intermediate-risk prostate cancer, but it can improve biochemical control and rates of tumor metastasis, researchers reported of the first large-scale study to examine whether hiked radiation doses are linked to improved survival.

A team led by Jeff M. Michalski, MD, of the Washington University School of Medicine in St. Louis, analyzed 1,499 prostate cancer patients, according to the study, half of whom were randomized to experimentally high radiation dose therapy at 79.2 Gy in 44 sessions and half of whom underwent standard radiotherapy at 70.2 Gy in 39 fractions.

At follow-up eight years later, overall survival rates were almost identical between cohorts, Michalski and colleagues wrote in JAMA Oncology—but the patients saw other crucial differences in their treatment. While survival for escalated radiotherapy and standard radiotherapy was 76 percent and 75 percent, respectively, the former group underwent fewer salvage therapies to control tumors that had grown or spread. They did, however, experience worse side effects.

“This randomized clinical trial showed that the overall survival of men treated for localized intermediate-risk prostate cancer was not improved with radiation dose escalation,” Michalski et al. wrote. “This is despite the fact that dose escalation significantly reduced the rates of biochemical failure, local progression and distant metastasis. Unlike previous randomized clinical trials evaluating dose escalation, this trial, the largest thus far, was powered to detect an overall survival difference in this patient population.” 

External-beam radiation therapy is an established treatment option for men with localized prostate cancer, the authors wrote, but in radiology’s nascent stages it’s been difficult to safely deliver high doses of radiation to the prostate without too much toxicity. This approach could be a more harmless way to improve biochemical and clinical cancer control, they said, even if it doesn’t improve survival.

“If we can safely deliver the higher dose of radiotherapy, my opinion is to do that,” Michalski said in a release from NRG Oncology. “It does show lower risk of recurrence, which results in better quality of life. But if we can’t achieve those ‘safe’ radiotherapy dose goals, we shouldn’t put the patient at risk of serious side effects down the line by giving the higher dose.”