|Dr. Babak Navi
Photo credit: Brooke Ismach
The findings, published Jan. 7 in the Annals of Neurology, are significant because they demonstrate that cancer increases the risk of stroke independently of other established stroke risk factors, such as high blood pressure or diabetes.
“These findings are relevant to patients and their care because stroke often leads to death and disability, especially if it is not quickly diagnosed and treated with clot-busting medicines,” said first author Dr. Babak Navi, an assistant professor of neurology and of neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell and a neurologist at Memorial Sloan Kettering Cancer Center. “Patients and their doctors should be vigilant for symptoms and signs of stroke and should immediately call 911 if they occur.
“In addition, stroke is particularly relevant to cancer patients because strokes often preclude or delay cancer treatments, resulting in reduced survival,” he added.
The researchers uncovered the link by reviewing Medicare claims submitted from 2001 to 2009 by patients ages 66 years or older diagnosed with breast, colorectal, lung and prostate cancer — the four most common malignant cancer types — as well as pancreatic cancer because clotting events including stroke are frequently associated with that type of tumor. Each patient was paired with someone of similar age, sex and comorbidities but who was cancer free to tease out the effect cancer has on stroke.
The investigators found that the cancer patients had a significantly elevated risk of stroke compared to their cancer-free cohorts, with the greatest risk in the first three months following diagnosis, when the intensity of chemotherapy, radiation and other therapies is generally highest.
In addition, the risk of stroke correlated with the aggressiveness of the cancer. For example, risk was highest among patients with lung, pancreas and colorectal cancers, which are often diagnosed at advanced stages. Patients with breast and prostate cancer, who often have localized tumors, had the lowest risk in the group.
While the study didn’t investigate the biological mechanisms behind the increased risk, the common theory is that cancer and its treatments affect blood vessels and the body’s clotting system, causing patients’ blood to thicken. The findings open up new lines of inquiry about the efficacy of blood thinners in this population, Dr. Navi said.
This study was done in collaboration with researchers at Memorial Sloan Kettering Cancer Center.