Multiple sclerosis (MS) may not be associated with developing breast cancer in pre- and postmenopausal women, according to a recent study.
While prior findings suggest a link between the diseases, new research points to an alternative link between breast cancer and MS. Their findings suggest that surveillance bias as a risk factor for breast cancer diagnosis, rather than multiple sclerosis itself.
Other studies have not taken tumor characteristics other than size into account, such as cancer stage or menopausal status. It has been thought that cancer risk is decreased in patients with multiple sclerosis with few exceptions, other than an increased risk for bladder cancer.
In-depth research about a link between breast cancer and multiple sclerosis has not yet delivered clear results.
Included in the current study published by PLOS One were 19,330 patients with multiple sclerosis. Investigators included both pre and postmenopausal women in the study to determine the risks in both groups of women.
Patients with multiple sclerosis were matched with 193,458 control patients who did not have the disease. They were matched by age, gender, geographic location, and overall health status.
Among patients with multiple sclerosis, 87 premenopausal and 384 postmenopausal patients developed breast cancer. There were 942 premenopausal and 4811 postmenopausal control patients who also developed breast cancer, according to the study.
These findings suggest that there is no significant relationship between premenopausal patients with multiple sclerosis and breast cancer. However, they did find that postmenopausal patients with multiple sclerosis had a moderately higher risk (13%) of developing breast cancer compared with their counterparts from the control group (HR = 1.13, 95% CI 1.02—1.26).
Interestingly, they discovered a 21% increase in the risk of breast cancer among postmenopausal women who were diagnosed with multiple sclerosis between 1968 and 1980 and those who were diagnosed at age 65-years-old and older, according to the study.
Patients diagnosed with breast cancer at older ages tended to have less advanced disease compared with younger patients, which the researchers said suggests surveillance bias. Since patients with multiple sclerosis require additional monitoring than someone without the disease, they are more likely to have their tumors detected at a very early stage.
The association between cancer diagnoses and patients with multiple sclerosis who were diagnosed before 1980 was attributed to prevalence cancer, and researchers did not believe this finding to be statistically significant, according to the study.
“Some previous studies have reported that the risk of cancer is increased among MS patients who have been treated for their disease,” the researchers concluded. “Our results argue against a major influence of MS therapies on risk of breast cancer.”