Background: Use of androgen suppression therapy (AST) in prostate cancer increased more than threefold from 1991 to 1999. The 2003 Medicare Modernization Act reduced reimbursements for AST by 64% between 2004 and 2005, but the effect of this large reduction on use of AST is unknown.
Methods: A cohort of 72,818 men diagnosed with prostate cancer in 1992-2005 was identified from the Surveillance, Epidemiology, and End Results database. From Medicare claims data, indicated AST was defined as 3 months or more of AST in the first year in men with metastatic disease (n = 8030). Non-indicated AST was defined as AST given without other therapies such as radical prostatectomy or radiation in men with low-risk disease (n = 64,788). The unadjusted annual proportion of men receiving AST was plotted against the median Medicare AST reimbursement. A multivariable model was used to estimate the odds of AST use in men with low-risk and metastatic disease, with the predictor of interest being the calendar year of the payment change. Covariates in the model included age in 5-year categories, clinical tumor stage (T1-T4), World Health Organization grade (1-3, unknown), Charlson comorbidity (0, 1, 2, ≥ 3), race, education, income, and tumor registry site, all as categorical variables. The models included variations in the definition of AST use (≥ 1, ≥ 3, and ≥ 6 months of AST). All statistical tests were two-sided.
Results: AST use in the low-risk group peaked at 10.2% in 2003, then declined to 7.1% in 2004 and 6.1% in 2005. After adjusting for tumor and demographic covariates, the odds of receiving non-indicated primary AST decreased statistically significantly in 2004 (odds ratio [OR] = 0.70, 95% confidence interval = 0.61 to 0.80) and 2005 (OR = 0.61, 95% confidence interval = 0.53 to 0.71) compared with 2003. AST use in the metastatic disease group was stable at 60% during the payment change, and the adjusted odds ratio of receiving AST in this group was unchanged in 2004-2005.
Conclusions: In this example of hormone therapy for prostate cancer, decreased physician reimbursement was associated with a reduction in overtreatment without a reduction in needed services.