In an analysis of the NRG Oncology clinical trial NRG-RTOG 9202 it was shown that the interval of time to biochemical reoccurrence (PSA only or BCR), or the time it takes for previously treated prostate cancer to return as indicated by a prostate-specific antigen (PSA) rise, could be used as a surrogate endpoint for survival for men with locally advanced prostate cancer.
Traditionally, surrogate endpoints were only based on PSA, which could determine the effectiveness of the primary treatment earlier than traditional clinical endpoints. However, surrogate endpoints for long-term success using androgen deprivation (ADT), a proven therapy in high-risk, localized cancers, has not been investigated.
According to James Dignam, Ph.D., of the Department of Public Health Sciences at University of Chicago and the NRG Oncology Statistics and Data Management Center, a member of the Cancer Prevention and Control research program at the University of Chicago Medicine Comprehensive Cancer Center, and the lead author of the NRG-RTOG 9202 analysis, it was demonstrated that the time interval between treatment and a biochemical failure could stand as a surrogate endpoint for the effect of long-term androgen deprivation (ADT) on two clinical endpoints: prostate cancer-specific survival and overall survival.
NRG-RTOG 9202 randomly assigned 1,520 men to one of two treatment arms.
Treatment Arm 1 received short-term androgen deprivation (ADT) therapy for four months, and Treatment Arm 2 received long-term AD for approximately 28 months.
According to Dr. Dignam, "Men who remained free of biochemical failure for three years had significantly more favorable overall survival and prostate cancer-specific survival. Additionally, data showed that 50% of the men who experienced biochemical failure by three years died of prostate cancer within15 years, as opposed to 19% among the men who were still free of biochemical failure at three years."
James J. Dignam et al. Time Interval to Biochemical Failure as a Surrogate End Point in Locally Advanced Prostate Cancer: Analysis of Randomized Trial NRG/RTOG 9202, Journal of Clinical Oncology(2018). DOI: 10.1200/JCO.18.00154
