Association between incident cancer and subsequent stroke

Objective: A study was undertaken to examine the association between incident cancer and the subsequent risk of stroke.

Methods: Using the Surveillance, Epidemiology, and End Results-Medicare linked database, we identified patients with a new primary diagnosis of breast, colorectal, lung, pancreatic, or prostate cancer from 2001 through 2007. These patients were individually matched by age, sex, race, registry, and medical comorbidities to a group of Medicare enrollees without cancer, and each pair was followed through 2009. Validated diagnosis codes were used to identify a primary outcome of stroke. Cumulative incidence rates were calculated using competing risk survival statistics.

Results: Among 327,389 pairs of cancer patients and matched controls, the 3-month cumulative incidence of stroke was generally higher in patients with cancer. Cumulative incidence rates were 5.1% (95% confidence interval [CI] = 4.9-5.2%) in patients with lung cancer compared to 1.2% (95% CI = 1.2-1.3%) in controls (p < 0.001), 3.4% (95% CI = 3.1-3.6%) in patients with pancreatic cancer compared to 1.3% (95% CI = 1.1-1.5%) in controls (p < 0.001), 3.3% (95% CI = 3.2-3.4%) in patients with colorectal cancer compared to 1.3% (95% CI = 1.2-1.4%) in controls (p < 0.001), 1.5% (95% CI = 1.4-1.6%) in patients with breast cancer compared to 1.1% (95% CI = 1.0-1.2%) in controls (p < 0.001), and 1.2% (95% CI = 1.1-1.3%) in patients with prostate cancer compared to 1.1% (95% CI = 1.0-1.2%) in controls (p = 0.085). Excess risks attenuated over time and were generally no longer present beyond 1 year.

Interpretation: Incident cancer is associated with an increased short-term risk of stroke. This risk appears highest with lung, pancreatic, and colorectal cancers.