Characterizing and assessing antiemetic underuse in patients initiating highly emetogenic chemotherapy

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.

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.

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.

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.