ASPO Abstracts
Association between concomitant hydrochlorothiazide use and neutropenia-related hospitalizations among older breast and colon cancer patients treated with chemotherapy
Category: Survivorship & Health Outcomes/Comparative Effectiveness Research, Survivorship & Health Outcomes/Comparative Effectiveness Research
Conference Year: 2018
Abstract Body:
Limited evidence suggests that use of hydrochlorothiazide (HCTZ), a blood pressure medication, concomitant with 5-fluorouracil (5FU) or cyclophosphamide increases myelosuppression. Using cancer registry and claims data, we investigated the association between concomitant HCTZ use and neutropenia-related hospitalizations among cyclophosphamide-treated breast and 5FU-treated colon cancer patients. Adults with a first primary stage I-III breast or II-III colon cancer over age 65 and initiating adjuvant chemotherapy with cyclophosphamide or 5FU were identified using the Surveillance, Epidemiology, and End Results-Medicare data. Concomitant HCTZ use was defined as any overlap between HCTZ days’ supply and initiation of chemotherapy. Neutropenia-related hospitalizations within 6-months were identified using primary and secondary diagnosis codes. Potential confounders included age, sex, race, stage, other chemotherapies (anthracyclines, taxanes, oxaliplatin), Charlson comorbidity score, predicted frailty, and polypharmacy. Cox proportional hazards models were used to estimate unadjusted and adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for HCTZ use and neutropenia-related hospitalization. We identified 2,045 breast and 2,079 colon cancer patients who initiated adjuvant chemotherapy containing cyclophosphamide or 5FU, respectively. In addition to cyclophosphamide, 40% and 60% of breast patients were treated with an anthracycline or taxane, respectively. In addition to 5FU, 56% of colon patients were treated with oxaliplatin. Overall, 27% of breast and 17% of colon cancer patients were exposed to HCTZ and 11% and 4% were hospitalized for neutropenia within 6 months. In the breast cohort, there was no association between HCTZ use and neutropenia-related hospitalization before (HR=0.98, 95% CI: 0.73, 1.31) or after adjustment (aHR=0.97, 95% CI: 0.73, 1.30). Results were similar in the colon cohort (HR=1.04, 95% CI: 0.61, 1.78; aHR=1.06, 95% CI: 0.61, 1.84). Neutropenia- related hospitalizations were more common among breast than colon cancer patients. Despite being listed as a potential drug-drug interaction in pharmacy reference databases, we found no evidence for an increased risk of neutropenia-related hospitalizations associated with HCTZ use.
Keywords: chemotherapy, drug interactions, Medicare beneficiaries