Investigating racial disparities in use of NK1 receptor antagonists to prevent chemotherapy-induced nausea and vomiting among breast cancer patients.

292 Background: Chemotherapy-induced nausea and vomiting (CINV) is a major concern for cancer patients and, if uncontrolled, it can have serious implications for patients' treatment outcomes, including quality of life. Guidelines recommend the use of an NK1 receptor antagonist to prevent CINV among patients beginning chemotherapy with a high risk of causing the side effect. However, barriers to use of oral NK1s (i.e., aprepitant) exist. In many cases, patients are required to fill a prescription for aprepitant at their home pharmacy. As well, the drug is expensive, costing over $500 under Medicare Part D, and patients may be responsible for a large portion of that cost. These barriers may contribute to racial disparities as they disproportionately affect minority patients.

METHODS: We used 2006-2012 SEER-Medicare data to evaluate the use of NK1s among black and white women initiating adjuvant chemotherapy with an anthracylcline and cyclophosphamide for early-stage breast cancer. NK1 use during the first chemotherapy cycle was measured using Medicare Part D and Part B claims. We used modified Poisson regression to assess the relationship between race and (1) any NK1 use, (2) oral NK1 (aprepitant) use, and (3) intravenous NK1 (fosaprepitant) use. We report adjusted risk ratios (aRR) and 95% confidence intervals (CI).

RESULTS: Of 1,015 eligible women (911 white; 104 black), 38% of white and 28% of black women received any NK1 at the start of their chemotherapy regimen. In adjusted analyses, black women were 30% less likely than white women to receive any NK1 (aRR black vs. white: 0.70, 95% CI: 0.52-0.94). This disparity was driven by a 44% gap in orally administered NK1s (aprepitant) (aRR: 0.56 95% CI: 0.35-0.89). We did not observe disparities in intravenous fosaprepitant use (aRR: 0.77, 95% CI: 0.46-1.28, NS). After controlling for variables related to socioeconomic status, disparities in NK1 and aprepitant use were reduced but not eliminated.

CONCLUSIONS: Our study found racial disparities in women's use of oral NK1s for the prevention of CINV. These disparities may be partly explained by racial differences in women's ability to afford the medication.