Short-term hormone therapy added to radiation increases survival for medium-risk, but not low-risk, prostate cancer patients

Short-term hormone therapy given prior to and during radiation treatment to medium-risk prostate cancer patients increases their chance of living longer, compared to those who receive radiation alone, however there is no significant benefit for low-risk patients, according to the largest randomized study of its kind presented at the plenary session November 2, 2009, at the 51st Annual Meeting of the American Society for Radiation Oncology (ASTRO).

This phase III study is one of the largest clinical trials of prostate cancer therapy ever completed, with 2,000 low- and intermediate-risk patients enrolled in the trial from October 1994 to April 2001. Researchers from the Radiation Therapy Oncology Group (RTOG) followed men with early-stage prostate cancer for a period in most cases of more than nine years. This timeframe was sufficient to show improved survival benefits of short-term hormone therapy added to what was then the standard radiation treatment for prostate cancer, which involved slightly lower doses of radiation than are currently used today with newer techniques, such as intensity modulated radiation therapy (IMRT).

"The study provides strong scientific evidence that shows us when to deliver hormone therapy with radiation in patients with localized prostate cancer," Christopher U. Jones, M.D., an author of the study and a radiation oncologist at Radiological Associates of Sacramento in Sacramento, Calif., said. "Our findings show that men with low-risk disease, which is the vast majority of prostate cancer patients, have little to gain from adding hormone therapy to radiation. However, men with intermediate-risk disease, which is a significant minority of patients, gain a benefit in overall survival from the addition of only four months of hormone therapy. Prior to this trial, it was unclear whether or not combining hormone therapy with radiation for medium-risk prostate cancer patients improves survival."

Androgen deprivation therapy is hormone therapy used to treat prostate cancer by stopping or lowering the level of male hormones, or androgens, thereby removing the strongest growth factor for prostate cancer cells.

In the study, a total of 1,979 eligible men who had cancer confined to the prostate and a PSA less than or equal to 20 were randomized to receive total androgen deprivation therapy two months prior to and two months during radiation treatment, or radiation alone.

Findings show that short-term hormone therapy given to early-stage prostate cancer patients prior to and during radiation treatment significantly increases their chance of living longer (51 percent), compared to those who receive radiation alone (46 percent). Nearly all of the survival benefit was in the intermediate-risk group. Secondary endpoints of disease-free survial, freedom from biochemical failure, and positive two year re-biopsy rates were also better in the group who received short-term hormone therapy and radiation treatment.

The study was supported by grants from the National Cancer Institute.

For more information on radiation therapy for prostate cancer, visit www.rtanswers.org.