Is Atrial Fibrillation a Risk Factor for Cancer?

Atrial fibrillation (AF) may raise cancer risk, according to a study published in JAMA Cardiology.¹

David Conen MD, MPH, of University Hospital in Basel, Switzerland, and colleagues conducted a 20-year prospective cohort study evaluating the associations between AF and cancer in 34 691 women 45 years of age or older, who were free of cardiovascular disease (CVD) and cancer at baseline.  Data on these patients were derived from the Women’s Health Study, a randomized trial of aspirin and vitamin E for the prevention of CVD and cancer. 

During the study period, new-onset AF and malignant cancer were confirmed among 1467 (4.2%) and 5130 (14.8%) patients respectively. The median baseline age of those with new-onset AF and new-onset cancer during follow-up was 58 years and 55 years, respectively.

In age-adjusted and multivariable-adjusted models, AF was a significant risk factor for incident cancer, with the highest relative risk occurring in the first 3 months after onset. However the risk remained significant even beyond 1 year, with an observed trend toward increased cancer mortality. The association was strongest with colon cancer.

Among women with new-onset cancer, the relative risk of AF was increased as well, but only within the first 3 months following cancer diagnosis.

“Shared risk factors and/or common systemic disease processes might underlie this association,” the authors wrote. For example, AF may be “an early sign of occult cancer.” Inflammation or oxidative stress “could represent combined predisposing processes,” and “both diseases processes are associated with prothrombotic states.”

An accompanying editorial² by researchers at Boston University described this study as “provocative,” because it raises the question as to whether AF is a risk factor for cancer. “The term risk factor often implies a causal relationship between the exposure and the outcome,” the authors noted. In this case, however, “AF most likely serves as a risk marker for future diagnosis of cancer.”

The authors explored whether a diagnosis of AF should “prompt a search for occult cancer” and concluded that, “based on available data, cancer screening beyond standard routine health care is currently not merited with a new diagnosis of AF.”

They added, “Understanding the intermediate steps that link AF and cancer in the bidirectional associations reported by Conen et al may provide valuable mechanistic and therapeutic insights with regard to both conditions.”

References

1. Conen D, Wong  JA, Sandhu  RK,  et al.  Risk of malignant cancer among women with new-onset atrial fibrillation. JAMA Cardiol. 2016;1(4):389-396. doi:10.1001/jamacardio.2016.0280.
2. Rahman F, Ko D, Benjamin EJ. Association of atrial fibrillation and cancer. JAMA Cardiol. 2016;1(4):384-386. doi: 10.1001/jamacardio.2016.0582.