Atrial fibrillation as a marker of occult cancer

BACKGROUND: Recent studies suggest that cancer increases risk of atrial fibrillation. Whether atrial fibrillation is a marker for underlying occult cancer is unknown. METHODS: We conducted a cohort study (1980-2011) of all Danish patients with new-onset atrial fibrillation. To examine cancer risk, we computed absolute risk at 3 months and standardized incidence ratios (SIRs) by comparing observed cancer incidence among patients newly diagnosed with atrial fibrillation with that expected based on national cancer incidence during the period. RESULTS: Median follow-up time was 3.4 years among 269 742 atrial fibrillation patients. Within 3 months of follow-up, 6656 cancers occurred (absolute risk, 2.5%; 95% confidence intervals [CI], 2.4%-2.5%) versus 1302 expected, yielding a SIR of 5.11; 95% CI, 4.99-5.24. Associations were particularly strong for cancers of the lung, kidney, colon, ovary, and for non-Hodgkin's lymphoma. The SIR within 3 months of follow-up was 7.02; 95% CI, 6.76-7.28 for metastatic and 3.53; 95% CI, 3.38-3.68 for localized cancer. Beyond 3 months of follow-up, overall cancer risk was modestly increased (SIR, 1.13; 95% CI, 1.12-1.15). CONCLUSION: Patients with new-onset atrial fibrillation had a markedly increased relative risk of a cancer diagnosis within the next three months, however, corresponding absolute risk was small

Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) for all cancer sites following atrial fibrillation by follow-up period, Denmark, 1980–2011.

<p>Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) for all cancer sites following atrial fibrillation by follow-up period, Denmark, 1980–2011.</p

Standardized incidence ratios for major cancer sites or lifestyle-related cancers diagnosed following atrial fibrillation by follow-up period, Denmark, 1980–2011.^a^,^b

a<p>SIR, standardized incidence ratio; CI, confidence interval.</p>b<p>Because only the 13 most incident cancers for each gender (The Danish Health and Medicines Authority, 2010) are shown, the number of cases for the individual sites and types do not add up to the total number.</p

Standardized incidence ratios for all cancers diagnosed following atrial fibrillation, stratified according to covariates, Denmark, 1980–2011.^a

a<p>SIR, standardized incidence ratio; CI, confidence interval.</p