Background
Four practice guidelines incorporate the use of gene expression profiling (GEP) tests for early-stage, hormone-receptor positive, HER2 negative breast tumors. Few studies describe factors associated with GEP testing in US oncology practice. We assessed the relationship between clinical, demographic, and group-level socioeconomic variables and test use in women under age 65.
Patients and Methods
Data from five state cancer registries were linked with insurance claims data and GEP test results. We assessed rates of testing and variables associated with test use in an incident cohort of 9444 commercially-insured women under age 65, newly-diagnosed with Stage I or II hormone-receptor positive breast cancer from 2006–2012.
Results
Rates of testing for women with N0 disease increased from 20.4% in 2006 to 35.2% in 2011. Variables associated with higher rates of testing, beyond clinical factors such as nodal status (P < .001), included being diagnosed from 2008–2012 vs. 2006–2007 (adjusted odds ratio, 1.67; 95% CI, 1.47 to 1.90), having preexisting comorbidities (adjusted odds ratio, 1.35; 95% CI, 1.14 to 1.59), and higher out-of-pocket pharmacy costs (adjusted odds ratio, 1.66; 95% CI, 1.40 to 1.97). Women under age 50 were more likely to be tested if they had Stage I vs. Stage II disease (P < .0001).
Conclusions
In an insured population of women under age 65, GEP testing increased following its inclusion in guidelines and mounting evidence. Additional research is needed to better understand oncologists’ decision not to order GEP testing for their patients who are otherwise eligible.