We conducted a national claims—based study of Medicare beneficiaries age ≥ 66 years. We assessed trends in assay use (using multivariable regression), adjuvant chemotherapy use, and associated expenditures, for all patients and for two age strata: age 66–74 years and 75–94 years. Geographic variations in assay adoption and regional-level correlation between assay and chemotherapy use were measured.
We identified 132,222 women who underwent breast surgery from 2008–2011. Assay use increased from 9.0% to 17.2% from 2008–2011 (p < .001), but chemotherapy use remained stable at 12.5% (p = .49). In younger patients, assay use increased from 14.3% to 23.7% (p < .001), while chemotherapy use decreased from 18.2% to 16.2% (p < .001). In older patients, assay use increased from 4.1% to 9.9% (p < .001), while chemotherapy use remained stable at 6.8% (p = .67). Mean per-beneficiary expenditures for testing and chemotherapy increased from $2030 to $2430 (p < .001). Regions with increased assay adoption were not more likely to reduce chemotherapy.
Despite increased RS testing for both younger and older Medicare patients, there has only been a modest decrease in chemotherapy use for younger patients and no change for older patients, resulting in an overall increase in costs associated with gene expression profiling.