A Phase III study presented at ASCO's 46th Annual Meeting reports that adding radiation therapy to androgen deprivation therapy (ADT; also known as hormone therapy) reduces the risk of dying from prostate cancer by 43 percent in men with locally advanced or high-risk prostate cancer compared to ADT alone.

"This study will challenge the prevailing dogma of only using hormone therapy for locally advanced prostate cancer," said Padraig Warde, MBChB, deputy head of the radiation medicine program at the University of Toronto's Princess Margaret Hospital. "We found that men who received the combination lived longer, and were less likely to die of their prostate cancer than those who had only hormone therapy. These results suggest that adding radiation therapy to the treatment plan for these patients could become part of standard therapy and should be considered."

Some physicians and clinical guidelines recommend radiation with ADT as a treatment option for locally advanced prostate cancer. But it has been unclear whether ADT alone was sufficient therapy for these patients, and whether the side effects of radiation could be avoided. ADT reduces the level of cancer-fueling male hormones in the body, and is standard therapy for men whose disease persists despite local treatment (radiation therapy or surgery).

In this study, men with locally advanced or high-risk prostate cancer were randomly assigned to receive ADT alone (602 men) or ADT plus radiation (603 men). After 7 years, 66 percent of men who had ADT alone were still alive, compared with 74 percent of those who had received ADT plus radiation. Among those in the ADT-only group, 26 percent died from their prostate cancer, versus 10 percent of those who received ADT plus radiation. Patients who received ADT plus radiation lived 6 months longer on average than those who received ADT alone. There was no increase in significant, long-term GI toxicity between treatment groups.

The researchers projected that fewer men (15 percent) who received ADT plus radiation would die from their prostate cancer over 10 years (10-year cumulative disease specific death rate) compared to 23 percent with ADT alone.