A shorter course of androgen suppression therapy prior to radiation therapy, when compared to an extended course of androgen suppression therapy, yields comparable outcomes and fewer adverse effects for intermediate-risk prostate cancer patients, according to research presented recently at the 55th Annual Meeting of the American Society for Radiation Oncology (ASTRO).1 The study confirmed a disease-specific survival rate of 95% when patients received fewer weeks of neoadjuvant total androgen suppression.
The multi-institutional phase III trial, Radiation Therapy Oncology Group (RTOG) 9910, evaluated 1,490 patients with intermediate-risk prostate cancer from 152 institutions in the United States and Canada. Patients were accrued from 2000 to 2004 and followed for an average of 9 years. The average age of the men was 71 at the time of accrual. The patients were stratified and randomly assigned into two groups.
Group 1 consisted of 752 patients who received 8 weeks of neoadjuvant total androgen suppression, and group 2 consisted of 738 patients who received 28 weeks of neoadjuvant total androgen suppression. Both groups then received 8 weeks of external-beam radiation therapy and concurrent total androgen suppression.
Cumulative incidence was used to estimate and test efficacy for disease-specific survival, prostate-specific antigen (PSA) failure, locoregional tumor progression, and distant metastasis. Overall survival rates were estimated via the Kaplan-Meier method and efficacy tested with log rank.
There was no statistical difference in disease-specific survival between the two arms; there were 30 prostate cancer deaths in group 1, for a 10-year disease-specific survival rate of 95%, and 24 prostate cancer deaths in group 2, for a 10-year disease-specific survival rate of 96%. There were 200 additional deaths not attributable to prostate cancer in group 1 for a 10-year overall survival rate of 66%, and 196 such deaths in group 2, for a 10-year overall survival rate of 67%. By 10 years, 27% of patients had a PSA failure (using the newer RTOG-ASTRO definition of nadir plus 2 ng/dL), 5% had locoregional recurrence, and 6% had distant metastasis. Hot flashes and erectile dysfunction were more common in group 2.
“Sometimes, preliminary research leads us to assume that more treatment is better, but this study serves as a strong cautionary note to put the promising treatment to the test,” said Thomas Pisansky, MD, lead author of the study and Professor of Radiation Oncology at the Mayo Clinic in Rochester, Minnesota. “Overall, both groups had very, very good outcomes, but patients assigned to group 2 had more side effects from androgen suppression than [patients in] group 1, who received only 8 weeks of neoadjuvant total androgen suppression. Now, investigators know the upper boundary of how much androgen suppression is needed in this group of patients. The results have substantial importance because they can alter the research strategy to one in which investigation can now concentrate on ways to simplify the treatment and further reduce side effects.” ■
Disclosure: Dr. Pisansky reported no potential conflicts of interest.
1. Pisansky TM, Hunt D, Gomella LG, et al: Radiation Therapy Oncology Group 9910: Phase III trial to evaluate the duration of neoadjuvant total androgen suppression and radiation therapy in intermediate-risk prostate cancer. American Society for Radiation Oncology 55th Annual Meeting. Abstract 1. Presented September 23, 2013.