Adding Radiation to Antiandrogen Hormone Therapy Extends Survival in Patients with High-Risk Prostate Cancer

Phoebe Starr

February 2014, Vol 5, No 1 - Genitourinary Cancers Symposium


San Francisco, CA—Radiation added to hormone therapy with antiandrogens extended cancer-specific survival, as well as overall survival, when used as the primary treatment of patients with locally advanced or high-risk prostate cancer. In the Scandinavian Prostate Cancer Group VII study, 10- and 15-year survival improved by more than 50% in patients who received radiation plus hormone therapy versus hormone therapy alone, according to an updated analysis presented at the 2014 Genitourinary Cancers Symposium.

Over time, the survival difference between the 2 arms grew larger. A 2009 analysis of this study showed that at 8 years, prostate cancer–specific mortality was reduced by 12% in the group receiving radiation plus hormonal therapy versus hormonal therapy alone.

Lead investigator Sophie D. Fosså, MD, PhD, Professor and Senior Researcher, Department of Oncology, Oslo University Hospital, Norway, explained that the study was initiated in 1996, when the standard therapy for locally advanced or high-risk prostate cancer was lifelong hormonal therapy alone; it is still standard in Scandinavia. “Lifelong therapy with antiandrogens improves survival,” Dr Fosså said.

At the time the study was initiated in 1996, prostate cancer that extended through the prostatic capsule was considered inoperable, she continued, and although surgical techniques have improved since then, surgery is not typically used in Scandinavia for these patients.

“The combination of radiotherapy and hormone therapy more than doubled the 10-year and 15-year survival rate and confirms that this approach should be a standard curative option for men with this type of prostate cancer who have at least another 10-year life expectancy,” Dr Fosså told listeners at a press cast.

Updated, Long-Term Results
The updated analysis was based on 11 years of observation of mortality data from the Norwegian and Swedish death registries. The 875 patients enrolled in the trial (aged <75 years) had locally advanced or high-risk prostate cancer, and a prostate-specific antigen level ≤70 mg/L. Patients were all in relatively good health, Dr Fosså said.

Both arms received medical castration alone for 3 months, and patients were then randomized to standard treatment with lifelong antiandrogens or to the same hormonal treatment plus radiation, consisting of 70 Gy to 74 Gy, to the prostate. That dose is considered high compared with doses used in the United States.

The 10-year prostate cancer–specific mortality was reduced by more than 50% when radiation was added—19% for antiandrogens alone versus 8% for antiandrogens plus radiation. The difference between the 2 arms was even greater at 15 years—31% mortality rate with antiandrogens alone versus 12% with the combination of radiation plus antiandrogens.

Looking at overall mortality, hormones plus radiation achieved superior results, but the gap between the 2 arms was narrower than for prostate cancer–specific mortality, because many patients died from other diseases, Dr Fosså added. The 10-year overall mortality rates were 35% for antiandrogens and 26% for the combination; the 15-year overall mortality rates were 57% and 43%, respectively.

Safety
Both treatment arms were associated with the adverse events that would be expected with these therapies, including impaired sexual function and bowel problems.

Press cast moderator Charles J. Ryan, MD, Associate Clinical Pro­fessor, Department of Medicine (He­matol­ogy/Oncology), University of California, San Francisco, said that this study was interesting, because the outcomes continued to improve over time, which is different from many other randomized trials. Dr Ryan emphasized that the men in this study received antiandrogens—not lifelong medical castration.