It is already widely known that being overweight or obese increases breast cancer risk for many women. For the first time, however, a study presented at this year’s RSNA (Radiological Society of North America) annual meeting (November 26-December 1) revealed that women with a higher BMI benefit more from breast screening, and at more frequent intervals.
“Our study suggests that when a clinician presents the pros and cons of breast cancer screening to the patient, having high BMI should be an important ‘pro’ argument, said study co-author Fredrik Strand MD. “In addition, our findings suggest that women with high BMI should consider shorter time intervals between screenings.”
Strand, a radiologist at the Karolinska University Hospital in Stockholm, Sweden, was not specific about the interval, although it should be pointed out that many European countries do not advocate annual mammographic screening like the United States (with the exception of the US Preventive Services Task Force).
The finding was uncovered while Strand was studying how breast density is associated with delayed detection. The study involves more than 2,300 women with invasive breast cancer between 2001 and 2008.
Information about the link between higher BMI and breast cancer risk can be a bit confusing. The risk increases with higher BMI in postmenopausal women, yet being overweight or obese is associated with a modest decreased breast cancer risk before menopause. This may have something to do with estrogen production and estrogen levels in the blood and fat tissue. Additionally, women who are heavier have higher levels of insulin in their bodies—higher levels of insulin and having type 2 diabetes are linked to a higher risk of breast cancer.
Interestingly, some data suggests that losing weight after menopause can also lower risk for developing breast cancer. One large study1 suggested that women who lost 4-11 pounds after menopause had at least a 20% lower risk of breast cancer when compared with women whose weight remained the same—although other studies have not confirmed this. And being overweight or obese increases the risk of death from breast cancer for those who have been diagnosed with it.
According to the CDC, the average American woman weighs 166.2 pounds, whereas the average European woman weighs around 146 pounds. If Dr. Strand’s conclusions are correct, it may explain the reason why American women and their doctors place more value on regular annual breast screening than their European counterparts… and why population-based studies that do not take BMI into account in Europe may have different conclusions than those performed in the United States.
The bottom line? Being overweight is a risk factor for breast cancer, and now the clinical research is showing that regular (or more frequent, depending on whose point of view you are using) screening with mammography is especially important in overweight women in order to achieve early detection.
1.Eliassen AH, Colditz GA, Rosner B, et al. Adult weight change and risk of postmenopausal breast cancer. JAMA. 296(2):193-201, 2006