Background: To assess the risk of lymphedema associated with the use of calcium channel blockers (CCB) among breast cancer patients. Methods: A nested case–control study of adult female breast cancer patients receiving an antihypertensive agent was conducted using administrative claims data between 2007 and 2015. Cases were patients with lymphedema who were matched to 5 controls based on nest entry date (±180 days), age (±5 years), number of hypertensive drug classes, Charlson Comorbidity Index (CCI), thiazide exposure, and insurance type. Exposure to CCBs and covariates was identified in the 180-day period prior to event date. Conditional logistic regression was used to assess the impact of exposure among cases and controls. Results: A total of 717 cases and 1,681 matched controls were identified. After matching on baseline characteristics, mastectomy (7.8% vs. 4.8%; P ¼ 0.0039), exposure to radiotherapy (27.1% vs. 21.7%; P ¼ 0.0046), taxane-based chemotherapy (11.7% vs. 7.4%; P ¼ 0.0007), anthracycline-based chemotherapy (6.0% vs. 3.6%; P ¼ 0.0073), CCB use (28.3% vs. 23.3%; P ¼ 0.0087), and CCI 19.8%) vs. 12.7%; P < 0.0001; score of 4 or above) were all higher in cases during the 180 days prior to the event date. In the adjusted analysis, CCB exposure was significantly associated with increased risk of lymphedema (OR ¼ 1.320; 95% confidence interval, 1.003–1.737). Conclusions: CCB use was significantly associated with the development of lymphedema in breast cancer patients. Impact: CCBs should be avoided or used with caution in breast cancer patients to reduce the risk for developing lymphedema.
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