Nearly 200,000 non-metastatic prostate cancer patients on androgen deprivation therapy

Key Points

Chicago-Nearly 190,000 men in the U.S. with non-metastatic prostate cancer were receiving continuous androgen deprivation therapy (ADT) at the end of 2008, according to the findings of a prevalence study reported at the American Society of Clinical Oncology annual meeting here.

The research used data from two large population-based databases, which were selected to represent important segments of the U.S. adult population and to cover a broad age range, along with population data from the U.S. Census. To provide a point-prevalence estimate of use in this setting at the end of 2008, men without evidence of metastatic disease (except to lymph nodes) were identified as actively receiving continuous ADT if they had been on a gonadotropin-releasing hormone (GnRH) agonist for at least the last 6 months of 2008 or had undergone bilateral orchiectomy prior to July 1, 2008 (thereby being continuously exposed to ADT for at least 6 months), explained first author Karynsa Cetin, MPH, senior manager at the Center for Observational Research at Amgen, Thousand Oaks, CA.

"There is a lot of information about incident use and trends of ADT use among men with localized prostate cancer in the Medicare population because of the changes in Medicare reimbursement that took place in 2004 and 2005. However, to our knowledge, this is the first comprehensive assessment of the prevalence of continuous ADT use in the non-metastatic setting at the national level. We were interested in addressing this gap in epidemiological information in order to understand how many non-metastatic patients might be at risk for the adverse effects of hormone therapy, and our data indicate that the number of recipients is not insignificant," said Cetin, who worked on the study with Thomas J. Arneson, MD, of the Chronic Disease Research Group in Minneapolis, and co-authors.

The data sources for the study included two large claims databases-the MarketScan Commercial Claims and Encounters Database (to represent men aged 18 to 64 years enrolled in fee-for-service [FFS] commercial health plans) and the Medicare 5% sample (to represent men aged ≥65 years enrolled in FFS Medicare). Although the analyses were performed to capture men receiving continuous ADT (treatment for ≥6 months), allowances were made for gaps in calendar time during treatment to account for real-world use of GnRH agonist regimens, which may not adhere to strictly regular schedules (eg, testosterone recovery may be used as a trigger to treat), Cetin explained.

Based on the observed prevalence in the two data sources and by applying person-level weights, prevalence of ADT use in the entire national commercially insured and FFS Medicare populations was estimated. Then, to account for men not represented in those two databases, the investigators made another extrapolation to the entire U.S. male population by applying the measured age-specific prevalence estimates to the U.S. Census population on Dec. 31, 2008.

"The strength of our study is that it used two very large population-based claims databases. However, as a limitation, it assumes the age-specific prevalence of ADT seen in these two databases holds true for men who are not captured in these cohorts, including those with private insurance or in the military, men who are uninsured, Medicaid beneficiaries without Medicare, or those enrolled in Medicare Advantage," Cetin said.

Prevalence increases with age

Based on the calculations, the point prevalence of continuous ADT use in men with non-metastatic prostate cancer on Dec. 31, 2008, was 11,935 (0.045%) in the U.S. commercially insured male population aged 45 to 64 years and 115,468 (1.055%) in the U.S. FFS male Medicare population aged 65 years or older. Prevalence of ADT use increased with increasing age, reaching 2.962% for the Medicare FFS male population aged 85 years and older. In the final estimates extrapolated to the U.S., 91% of the 188,916 ADT users were men aged 65 years and older, and men aged 75 years and older accounted for two-thirds.

Cetin and her co-authors have employment/leadership positions with, own stock, and/or have received research funding from Amgen.