Men who continued on hormonal therapy for at least five years after treatment with pelvic radiotherapy for locally advanced prostate cancer lived longer than men who discontinued their therapy sooner, according to a study from the Radiation Therapy Oncology Group (RTOG) published online prior to print in the Journal of Clinical Oncology.
RTOG investigators and other researchers have previously shown that adding androgen deprivation therapy (ADT) to pelvic radiotherapy improves survival for men with locally advanced prostate cancer, however the optimal duration of the hormonal therapy has not yet been established.
In a secondary analysis of a large randomized trial (RTOG 8531) that compared radiotherapy alone versus radiotherapy plus adjuvant ADT until disease progression, the authors identified a cohort of 189 patients who discontinued their assigned ADT despite no evidence of disease recurrence. The analysis found that men who continued ADT for five or more years had five- and 11-year overall survival rates of 100 and 63.9 percent, compared to 66.7 and 33.1 percent for those with more than one year and less than five years of ADT and 71.9 and 41.7 percent for men with less than one year of ADT.
The authors also reported improved disease-free survival and decreases in local failure and distant metastasis with ADT greater than five years. The results held even after adjusting for known prognostic variables such as age, prostate surgery, nodal status, stage and central review of Gleason scores, they wrote.
"Although our analysis gives strong support to the hypothesis that long-term hormonal therapy leads to better outcome than the standard two to three year regimen, it is clear that a well-designed randomized trial is needed to definitively answer this question," said the study's lead author Louis Souhami, MD, a professor in the department of radiation oncology at McGill University in Montreal.