2F-2 COMPARATIVE SURVIVAL BENEFITS FROM INTERMITTENT VERSUS CONTINUOUS ANDROGEN DEPRIVATION THERAPY IN ADVANCED PROSTATE CANCER PATIENTS: A POPULATION-BASED STUDY

Monday, October 24, 2016: 4:15 PM
Bayshore Ballroom Salon F, Lobby Level (Westin Bayshore Vancouver)

Huei-Ting Tsai, PhD1, George Philips, MD, MPH2, Ruth Pfeiffer, PhD3, David Penson, M.D.4, Alex Fu, PhD1, Yingjun Zhou, MS1 and Arnold Potosky, PhD1, (1)Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC, (2)Department of Medicine, Georgetown University Medical Center, Georgetown University, Washington D.C., USA, Washington, DC, (3)National Cancer Institute, Rockville, MD, (4)Vanderbilt University, Nashville, TN
Purpose: To provide population-based data for a long-standing debate on comparative survival benefit of intermittent and continuous androgen deprivation therapy (IADT versus CADT) among patients with advanced prostate cancer (PCa).

Methods: Using the linked SEER-Medicare data, we conducted a retrospective cohort study of 5,377 advanced PCa patients aged 66 or older diagnosed between 2002-2011 receiving ADT as primary treatment. The study cohort included two patient subgroups: 3,513 men with incident metastatic PCa at diagnosis and 1,864 men with salvage ADT after initial curative-intent therapy for localized disease (non-metastatic group). We obtained 5-year mortality outcomes, including all-cause and PCa death for the metastatic group and non-PCa and cardiovascular death for the non-metastatic group, via state death certificate data obtained by the SEER program. The CADT group included men who continued receiving ADT without any treatment gaps longer 3 months. IADT group included men who had a gap of more than 3 months between two subsequent ADT injections with the first gap within 18 months after ADT initiation and at least one PSA measurement or physician visit between the two ADT injections. We used Cox-proportional hazard models to estimate hazard ratios and 95% confidence intervals of each survival outcome between IADT versus CADT group. We also conducted matched propensity score analysis to address potential bias in patient selection for treatment in an observational setting. 

Results: Compared with the CADT group, men in IADT group had similar 5-year risk of all-cause death (HR=0.90, 95%C.I. = 0.82, 1.00, p=0.05) but a lower risk of PCa death (HR= 0.80, 95%C.I. = 0.70, 0.92, p=0.002). Among non-metastatic patients, we found a lower risk of non-prostate cancer (HR=0.59, 95%C.I. = 0.34, 1.01, p=0.06) and cardiovascular death (HR=0.77, 95%C.I. = 0.51, 1.17, p=0.22) in IADT group than in CADT group although the difference did not reach statistical significance. We obtained similar estimates in our sensitivity analysis. 

Conclusions: IADT for elderly men with advanced PCa provides similar overall survival benefit as CADT and may potentially reduce PCa death in men newly diagnosed with metastatic PCa. Among men receiving salvage ADT for managing localized disease progression, IADT and CADT may have similar risk of cardiovascular and non-prostate cancer death. This information may facilitate decision-making regarding use of IADT or CADT for treating advanced PCa.

See more of: ORAL ABSTRACTS: POPULATION HEALTH RESEARCH

See more of: 38th Annual North American Meeting of the Society for Medical Decision Making