Patient costs of breast cancer endocrine therapy agents under Medicare Part D vs with generic formulations

The high expense of newer, more effective adjuvant endocrine therapy agents (aromatase inhibitors [AIs]) for postmenopausal breast cancer contributes to socioeconomic disparities in breast cancer outcomes. This study compares endocrine therapy costs for breast cancer patients during the first five years of Medicare Part D implementation, and when generic alternatives became available.

The out of pocket patient costs for AIs and tamoxifen under Medicare Part D drug plans were determined for 2006-2011 from the CMS Website for the 50 US states and District of Columbia.

Between 2006 and 2010, the mean annual patient drug cost under Medicare Part D in the median state rose 19% for tamoxifen, 113% for anastrozole, 89% for exemestane, and 129% for letrozole, resulting in median annual out of pocket costs in 2010 of $701, $3050, $2804, and $3664 respectively. However, the 2011 availability of generic AI preparations led to median annual costs in 2011 of $804, $872, $1837, and $2217 respectively. Not included in the reported patient costs, the mean monthly drug premiums in the median state increased 58% in 2011 compared to 2007.

The more effective AI agents became considerably more expensive during the first several years of the Medicare Part D program. Cost decreased with the introduction of generic agents, an intervention that was independent of the Part D program. It is unlikely that the Part D program ameliorated existing socioeconomic disparities in survival among breast cancer patients, but the availability of generic agents may do so.