NASHVILLE, TENNESSEE — Previous research has shown a link between cancer and subsequent stroke, but a new study found the reverse relationship — that patients who have had a stroke are at higher risk for cancer.
The study suggests that the incidence of cancer is 1.4 times higher among stroke survivors at 2 years than the general population, and that having cancer increases the risk for death by 3-fold in stroke survivors.
These results "hopefully help us to understand better that cancer and stroke are not mutually exclusive disease entities," as has previously been thought, lead author Adnan Qureshi, MD, professor of neurology, neurosurgery and radiology at the University of Minnesota, Minneapolis, told a press conference here.
"There is clearly a higher risk of cancer in patients with ischemic stroke as compared with the general population, and that higher risk of incident cancer explains in part why these patients have a higher chance of dying over the next few years compared to their counterparts who haven't developed a stroke," he added.
Further research is needed to explain this association, he said, and to determine whether there is a role for more active cancer screening in patients with ischemic stroke.
The research was presented during the International Stroke Conference (ISC) 2015.
Incident Cancer
For this analysis, the researchers looked at participants in the Vitamin Intervention for Stroke Prevention (VISP) study, a randomized, double-blind, multicenter clinical trial that included patients aged 35 years and older who had sustained a nondisabling stroke within the previous 120 days and had elevated levels of homocysteine. Their mean age was 66 years.
Over a 2-year period, 133 incident cancers occurred among the 3247 participants. The most common type was skin cancer (35.3%). Prostate cancer made up 18.0% of cancers (most participants — 2013 — were men).
At 1 year, the age-adjusted annual rate of cancer in patients with ischemic stroke was higher than in the general population and that this annual rate continued to be higher in these patients over 2 years (1301.7 per 100,000 persons vs 911.5 per 100,000; standardized incidence ratio [SIR], 1.4; 95% confidence interval [CI], 1.2 - 1.6).
After adjustment for potential confounders, there was a higher risk for death, fatal/disabling stroke or death, and the composite endpoint of stroke, coronary heart disease, and/or death among participants who developed incident cancer compared with those who were cancer free.
"Essentially, if you develop incident cancer you have a 3-fold higher likelihood of dying during the follow-up period," Dr Qureshi noted. "So there is also a mechanistic explanation with incident cancer, and the higher mortality that is experienced by these patients."
Risk for Cardiovascular Events in Stroke Patients With Cancer vs No Cancer
| Endpoint | Adjusted Odds Ratio (95% CI) | P Value |
| Fatal/disabling stroke or death | 2.3 (1.4 - 3.7) | .001 |
| Stroke, coronary heart disease, and/or death | 1.4 (1.0 - 2.2) | .04 |
| Stroke or coronary heart disease | 0.8 (0.5 - 1.5) | .6 |
| Death | 3.1 (1.8 - 5.4) | <.001 |
Similar Risk Factors
Commenting on the study, Daniel Lackland, PhD, professor and director of graduate training, Medical University of South Carolina, Charleston, and American Stroke Association spokesperson, said the study results make sense.
"I think this is a good study in the sense that it describes what we would be expecting from an epidemiological and particularly from a population type of a standpoint — that people that have a high risk of stroke and they've survived the stroke so they've actually had it and they have carried through would also be at high risk for cancer. This is typically because of the similar risk factors that are associated with both stroke and cancer."
Dr Qureshi agreed that cancer and cardiovascular disease may share common risk factors, for example, cigarette smoking. As well, there may be a "common substrate" for biological pathologic abnormalities related to ischemic stroke and cancer, he added.
For example, people who have cancer may be more thrombogenic, "so perhaps ischemic stroke is just a manifestation of the thrombogenic propensity at an earlier stage in patients with cancer who haven't been diagnosed with cancer yet," he said.
Robert Adams, MD, professor of neurology, Comprehensive Stroke and Cerebrovascular Center, Medical University of South Carolina, and a spokesperson for the American Heart Association/American Stroke Association, agreed on this point. "I think that's one of the key things in the paper. You just alluded to the idea that maybe the two are related to a common factor, and common factors that you might want to consider too could be things like telomere length and the general health of the person."
Increased Surveillance?
Increased surveillance is another possible link, Dr Adams suggested. Stroke survivors are likely under closer medical care than the general population and so their cancers may be more likely to be picked up, while the underlying rate may not be different from that in the general population, he suggested.
Dr Qureshi agreed that the intensity of surveillance may differ for patients already under medical care. "One thing that may actually support that hypothesis is the rate of detection of skin cancer — so perhaps these patients are just being examined more robustly," he pointed out. "While that may explain at least part of this differential risk, it also opens an avenue that perhaps increased surveillance is justified in patients with ischemic stroke, and perhaps a more rigorous and organized program should be in place for cancer screening."
Phillip Gorelick, MD, medical director, Hauenstein Neuroscience Center and clinical professor, translational science and molecular medicine, Michigan State University College of Human Medicine, Lincolnwood, who moderated a press conference here where these data were presented, said inflammation is another mechanism that needs highlighting because it may be "at the root" of the relationship.
"When you look at cancer, COPD [chronic obstructive pulmonary disease], cardiovascular disease, there is a common pathway of inflammation," he said.
Dr Gorelick noted that "this also cuts the other way" and that emerging literature shows patients who take aspirin as a cardiovascular preventive measure for 5 to 10 years have a reduced risk for cancer.
"That hasn't been cast in bronze," he said, "but there are actually molecular pathways for colonic cancer for example where it's been fairly worked out why the aspirin may work."
The authors have disclosed no relevant financial relationships.
International Stroke Conference (ISC) 2015. Abstract 210. Presented February 12, 2015.
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Cite this: Stroke Linked to Increased Cancer Risk - Medscape - Feb 18, 2015.
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