Characterizing and assessing antiemetic underuse in patients initiating highly emetogenic chemotherapy

BACKGROUND: Patients initiating highly emetic chemotherapy (HEC) are at a 90% risk of chemotherapy-induced nausea and vomiting (CINV). Despite guideline-concordant antiemetic prescribing preventing CINV in up to 80% of patients, studies suggest that guideline-concordant antiemetic regimen use by patients initiating HEC is sub-optimal. However, these studies have been limited to single-site or single-cancer type with limited generalizability. The objective of this study was to describe antiemetic fill regimens and to assess predictors of underuse in the USA.

METHODS: Our study population was adult patients under the age of 65 with cancer initiating intravenous HEC between 2013 and 2015 with employer-sponsored insurance in the IBM Watson/Truven MarketScan Commercial Claims database (N = 31,923). Descriptive statistics were used to explain antiemetic prescribing patterns, including antiemetic underuse. Modified Poisson regression was used to identify factors associated with antiemetic underuse.

RESULTS: Among individuals initiating HEC, 49% underused guideline-concordant antiemetics. Most classified as under-using lacked an NK1 fill. While dexamethasone and 5HT3A uptake was over 80%, olanzapine use was minimal. Having lower generosity for prescription and medical benefits (paying more versus less than 20% out-of-pocket) increased the underuse risk by 3% and 4% (RR,1.03; 95% CI,1.01-1.05; P = 0.01 and RR,1.04; CI, 1.00-1.09; P = 0.03), respectively. Additionally, compared to receiving chemotherapy in the physician office setting, patients were at a 28% (RR, 1.28; 95% CI, 1.25-1.30; P < 0.0001) higher underuse risk in the outpatient hospital setting.

CONCLUSION: Antiemetic underuse is high in patients initiating HEC, potentially leading to avoidable CINV events. We found that insurance generosity has a minimal effect on antiemetic guideline concordance in this population, suggesting discordance may be the result of site of care as well as gaps in provider knowledge or accountability.