3072 POSTER Impact of Adherence to Antiemetic Regimens on Outcome of Nausea and Vomiting Control Among Asian Breast Cancer Patients Receiving Anthracycline-based Chemotherapy

Abstract

Background: Non-adherence to oral anticancer agents has been identified as a prevalent behavior amongst breast cancer patients. However, the prevalence of non adherence to outpatient antiemetic regimens that are prescribed for delayed emesis prevention in breast cancer patients is limited in the literature. Hence, this study was conducted to evaluate the impact of adherence to delayed antiemetic regimens on chemotherapy induced nausea and vomiting (CINV) control in breast cancer patients, and to identify patient characteristics that may be associated with non-adherence to antiemetic regimens. Methods: This was a prospective, observational study conducted at the largest ambulatory cancer center in Singapore from December 2006 to January 2011. All breast cancer patients receiving anthracycline-based chemotherapy and standardized outpatient antiemetic regimens were recruited. On the day of chemotherapy, patients were given a standardized 5-day diary to document their emesis events and their demographics obtained via interview. Pearson Chi-square test and multiple logistic regression were performed to analyze the impact of adherence on CINV control. Results: A total of 361 eligible patients were included in the final analysis (mean = 50.0±8.9 years). Majority of the patients were Chinese (80.1%) and diagnosed with Stage 2 and above breast cancer (88.1%). Almost half of the patients (42.1%) were non-adherent to their prescribed delayed antiemetics regimens, with dexamethasone usage being the least adhered to (non adherence: 37.4%). After adjusting for potential confounders (ethnicity, education level and stage of disease), patients who were adherent to antiemetics were more likely to achieve complete CINV control (defined as no emetic episodes, no nausea, and no rescue therapy required) than patients who were non adherent (NNT=9.6; Adjusted OR=1.74, 95% CI: 1.01 3.01). In addition, young women aged between 21−40 years old, pursued higher education, and diagnosed with Stage 1 breast cancer were associated with non adherence to antiemetics (p < 0.05). Conclusion: This is the largest study to date to evaluate the prevalence of non-adherence to delayed antiemetics among breast cancer patients. Our findings indicate that a substantial amount of Asian breast cancer patients (42.1%) were not adherent to their antiemetic regimens, which may have resulted into poor control of CINV.