CHICAGO—Androgen deprivation therapy (ADT) plus external beam radiation should be the standard treatment approach for men with locally advanced prostate cancer, according to a large, randomized international trial.

New data presented at the American Society of Clinical Oncology annual meeting showed that this combination therapy reduced the risk of dying from prostate cancer by 43% in men with locally advanced or high-risk prostate cancer compared with ADT alone.

“This study will challenge the prevailing dogma of only using hormone therapy for locally advanced prostate cancer,” said Padraig Warde, MB, MRCPI, 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.”

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Some physicians and clinical guidelines recommend radiation with ADT as a treatment option for locally advanced prostate cancer. It has been unclear, however, whether ADT alone was sufficient therapy for these patients and whether the side effects of radiation could be avoided.

In the new study, the seven-year overall survival (OS) rate was 74% among the 603 patients treated with both radiation and androgen deprivation compared with 66% among the 602 men treated with hormone therapy alone, for a risk reduction of 23%. The seven-year disease-specific survival (DSS) rate was 90% for the combination treatment compared with 79% for ADT alone, for a risk reduction of 43%. In this trial, radiotherapy consisted of 45 Gy in 25 fractions over five weeks to the pelvis plus 20 to 24 Gy in 10 to 12 fractions over 2.0 to 2.5 weeks to the prostate.

A total of 320 deaths occurred in the total population of 1,205 patients, 175 of them in the ADT only arm and 145 among men receiving the combination therapy. Eighty-nine patients in the ADT-only group (26%) died compared with only 51 (10%) in the dual-therapy arm.

Patients who received ADT plus radiation lived six months longer on average than those who received ADT alone. The two treatment groups were similar with respect to significant, long-term GI toxicities.

An analysis of adverse events revealed that late severe toxicities were rare. Those affecting the genitourinary system were observed in 2.3% on men in each trial arm. Low-grade diarrhea and rectal bleeding were more common among patient who received radiation.

In recent years, ADT has been the primary treatment for men with locally advanced prostate cancer. According to the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) database, this was the first-choice option for the period 2004-2007.

In a separate phase 3 trial involving 875 men with locally advanced prostate cancer, researchers found that the 10-year disease-specific mortality rate was 23.9% for those treated with ADT alone and 11.9% for those treated with ADT plus radiation, according to a report in the Lancet (2009;373:301-308).