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Atrial Fibrillation in Breast Cancer Patients
Quick Takes
- This is a case-control study examining the incidence and predictors of atrial fibrillation (AF) in older women (>65 years) diagnosed with breast cancer identified in the SEER database and matched to Medicare enrollees.
- The annual incidence for AF in older women with breast cancer (>65 years) is 3.9%, with highest rate in the first 60 days after cancer diagnosis. Cancer stage and grade were risk factors for AF.
- Findings are in line with previous reports of a higher burden of AF in patients with various subtypes of cancer.
Study Questions:
What are the incidence, prevalence, risk factors, and impact on mortality of atrial fibrillation (AF) in a multi-ethnic cohort of breast cancer patients?
Methods:
The authors leveraged the Surveillance, Epidemiology, and End Results (SEER)-Medicare-linked database to identify women >65 years old with a new diagnosis of breast cancer from 2007–2014. These patients were individually matched 1:1 to Medicare enrollees without cancer by year of birth, race, geographic region, and Charlson comorbidity index (0 vs. ≥1). The index date for matching was selected as the pseudo-diagnosis date in noncancer controls. Identified pairs were followed for 1 year to identify a primary outcome of AF (defined using International Classification of Diseases [ICD] codes). Survival analysis was performed accounting for the competing risk of death. Subgroups stratified by cancer grade and treatment were examined.
Results:
This study included 85,423 breast cancer patients, of whom 9,425 (11.0%) had a diagnosis of AF. Prior to the breast cancer diagnosis, the median age of the cohort was 81 years. New-onset AF was diagnosed in 2,993 (3.9%) patients in a 1-year period after the breast cancer diagnosis (incidence 3.3%, 95% confidence interval [CI] 3.0–3.5%, at 1 year; higher rate in the first 60 days [0.6%/month]), compared to 1.8% (95% CI 1.6–2.0%) in controls.
Patients with new-onset or prior AF were older, were more likely to have received chemotherapy as the initially therapy, and to have advanced breast cancer. Cancer grade, stage, and treatments were independently associated with AF. New-onset AF after breast cancer diagnosis (adjusted hazard ratio, 3.00) is associated with increased 1-year cardiovascular mortality in those diagnosed within 30 days of breast cancer, but not in those with prior AF. There was no difference in breast cancer-specific mortality at 1 year between both groups.
Conclusions:
The incidence of AF is higher in women after a diagnosis of breast cancer compared to those without breast cancer.
Perspective:
This study follows several studies highlighting a higher incidence of AF in older women with breast cancer. This association however is not specific to breast cancer and has been observed across all subtypes of cancer. AF and cancer are linked through several shared pathophysiologic mechanisms and risk factors such as hypertension, obesity, and diabetes mellitus, which fall under the umbrella of chronic inflammatory processes. Cancer burden and therapy, notably systemic chemotherapy, are strong risk factors for AF, likely through exacerbation inflammation and direct damage to cardiovascular tissues.
Certain associations reported in this study however are difficult to explain. For example, cardiovascular medications were associated with a lower risk of developing AF, which is unusual given patients on these medications are likely to have a higher burden of cardiovascular risk factors and are perceived as higher risk than those not on therapy. Another unusual finding in this study is that despite having 3,000 patients with incident AF, only two underwent cardioversion, a rate much lower than one would expect based on current practice trends.
Overall, this study’s findings are in line with prior evidence of a higher burden of AF in patients with cancer. It remains an observational study that relies on case-control matching and ICD codes for diagnoses; major limitations for making any strong conclusions derived from secondary analyses.
Clinical Topics: Arrhythmias and Clinical EP, Cardio-Oncology, Geriatric Cardiology, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Hypertension
Keywords: Aged, 80 and over, Arrhythmias, Cardiac, Atrial Fibrillation, Breast Neoplasms, Cardiotoxicity, Diabetes Mellitus, Electric Countershock, Geriatrics, Hypertension, Inflammation, Obesity, Risk Factors, Secondary Prevention
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