Scottsdale, Ariz. — Obese women may be at risk for having breast cancer detected at a later stage and may have lower overall survival rates than non-obese women, according to a Mayo Clinic study presented at the 2010 American Society of Breast Surgeons annual meeting in Las Vegas.
The study found that obese women (defined as those with a body mass index of 30 percent or greater) were more likely to have breast cancer detected at a later stage, presenting with lymph node metastases at the time of diagnosis, than women who were not obese.
“The key factor was that even though most of the breast cancers were detected by mammogram, the obese women had larger tumors than the non-obese women. Because larger tumors were found, they also had a higher risk of lymph node metastasis and therefore a later stage cancer,” explained Barbara Pockaj, M.D., a surgeon at the Breast Clinic at Mayo Clinic in Arizona.
Despite the larger size of the tumors, compared to their non-obese counterparts, “It was harder to palpate (feel) the tumor,” said Dr. Pockaj. “If they (obese women) do not follow a yearly screening, they have a likelihood of not finding the tumor at an early stage.”
The study tracked 1,352 female patients who were treated for invasive breast cancer at Mayo Clinic during an 8-year time period. Of that study group, 76 percent of the patients were characterized as non-obese (with a BMI under 30 percent) while 24 percent were obese (with a BMI greater than 30 percent). The obese women tended to be older than their non-obese counterparts, which may be a reflection of the higher incidence of breast cancer among post-menopausal obese patients. There were no significant differences between both study groups with regard to family history of breast cancer or who had the BRCA 1 or BRCA 2 genetic mutations.
The study also found obese women with later stage breast cancer trended toward a worse overall survival rate, possibly a result of being diagnosed at a later stage combined with other co-morbidities associated with obesity, such as diabetes and hypertension.
Early detection, researchers say, is critical.
Some of the theory, explained Dr. Pockaj, is that studies have shown that obese women tend to schedule breast screenings less frequently than their non-obese counterparts. “Obese women need to follow the usual screening guidelines and should not be lax,” Dr Pockaj stressed.
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