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Beta-blockers may reduce breast cancer progression, death
Barron TI. J Clin Oncol. 2011;doi:10.1200/JCO.2010.33.5422.
Ganz PA. J Clin Oncol. 2011;doi:10.1200/JCO.2011.35.8820.
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Women taking the beta-blocker propranolol within a year of diagnosis of breast cancer were less likely to present with T4 tumor and were less likely to die of the disease compared with nonusers, according to results from an analysis of linked national cancer registry and prescription dispensing data.
Women taking the beta-blocker atenolol did not see a similar beneficial effect compared with nonusers.
Researchers identified 5,801 Irish women aged at least 40 years diagnosed with any stage invasive breast cancer from 2001 to 2006. Women taking propranolol, a B1/B2 antagonist (n=70), or atenolol, a B1 antagonist (n=525), in the year before diagnosis were matched with 4,738 women not taking a beta-blocker.
Median duration of propranolol exposure in the year before diagnosis was 232 days, and the median daily dose of propranolol was 80 mg.
There were four (8.9%) breast cancer-specific deaths among propranolol users, for an incidence rate of 26.5 per 1,000 woman-years vs. 20 (22.2%) deaths among nonusers matched by age, tumor grade, tumor stage and comorbidity, for an incidence rate of 67.9 per 1,000 woman-years. Five years after breast cancer diagnosis, the risk for breast cancer-specific mortality was 81% lower for propranolol users compared with nonusers (HR=0.19; 95% CI, 0.06-0.60).
Compared with nonusers matched by age, comorbidity and propensity score, propranolol users were significantly less likely to present with a T4 tumor at diagnosis compared with matched nonusers (OR=0.24; 95% CI, 0.07-0.85). Moreover, women taking propranolol were significantly more likely to present with grade 1 or 2 tumors at diagnosis (OR=2.33; 95% CI, 1.19-4.56).
Researchers said women taking propranolol were also less likely to present with N2/N3 nodal involvement or metastatic disease compared with matched nonusers (OR=0.20; 95% CI, 0.04-0.88).
Writing in an accompanying editorial, Patricia A. Ganz, MD, and Steven W. Cole, PhD, both of the Jonsson Comprehensive Cancer Center at UCLA, said there were some limitations in the study, but that the findings show that “the microenvironment may be a critical target for future cancer treatment and prevention of recurrence.”
“These provocative findings suggest that the benefits of beta-blocker therapy accrued only in the nonselective formulation, implicating the B2 adrenergic pathway as the likely mediator of the therapeutic benefit observed,” they wrote. “Limitations of this study include its retrospective design, the exclusion of more than 6,000 women in the tumor registry from analysis due to the fact that they were not in the pharmacy database, which served primarily older and low-income individuals, and the confounding by indication for the beta-blocker medications.”
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