In men with early-stage prostate cancer and a prostate specific antigen (PSA) level of 20 ng/mL or less, the use of androgen-deprivation therapy (ADT) for 2 months before and 2 months during radiation therapy was associated with significantly decreased disease-specific mortality and increased overall survival in a large, long-term study conducted by the Radiation Therapy Oncology Group (RTOG).
The trial involved 1,979 men, all with early-stage prostate adenocarcinoma (stage T1b, T1c, T2a, or T2b), who were treated at 212 facilities in the United States and Canada. After following the patients from October 1994 to April 2001 (median follow-up 9.1 years), Christopher U. Jones, MD, of Radiological Associates of Sacramento in Sacramento, California, and fellow RTOG investigators found that the 10-year rate of overall survival was 62% among men receiving radiotherapy plus short-term ADT, compared with 57% for those undergoing radiotherapy only (N Engl J Med. 2011;365:107-118). The addition of short-term ADT was linked with a reduction in 10-year disease-specific mortality from 8% to 4% (hazard ratio for radiotherapy alone was 1.87).
Further analysis of study data identified men as low-risk (Gleason score less than 6, PSA level less than 10 ng/mL, clinical stage less than T2a) or intermediate-risk (Gleason score of 7, or Gleason score of less than 6 with either PSA level of 10 ng/mL to less than 20 ng/mL or clinical stage T2b). Disease-specific mortality reduction was seen mostly in the intermediate-risk group (10% for the combination therapy patients vs 3% for radiation-only patients), whereas no reduction in deaths was seen among the low-risk participants at the 10-year mark.
The researchers noted that biochemical failure, distant metastases, and the rate of positive findings on repeat prostate biopsy at 2 years were significantly improved with radiotherapy plus short-term ADT. The incidence rate of hormone-related toxic effects of grade 3 or higher was 5%. Radiation-induced toxic effects were similar between the two groups.