Obese women are more likely to have bigger tumors and higher rates of lymph node metastases at the time of diagnosis than non-obese women, a new study finds.

Researchers at Mayo Clinic in Phoenix, Arizona, performed a retrospective review of a prospectively collected database of patients treated for invasive breast cancer at the institution from 2000 to 2008. In a total cohort of 1,352 patients identified, 76 percent were classified as non-obese and 24 percent as obese (BMI greater or equal to 30).

"The aim of our research was to analyze our experience at our institution and determine the differences in the obese patients who presented with breast cancer, differences with regard to presentation, tumor characteristics, treatment and outcomes," said Dr. Danielle Haakinson, lead researcher and surgical resident with the Mayo Clinic, in a conference call.
Researchers found that even though obese women had larger tumors, they were less likely to present on a self-breast exam or a physical check up than on an imaging exam. The mean size of a tumor in the obese group was 2 centimeters.

"Two-thirds of these women presented on imaging versus palpation," said Dr. Haakinson. "Furthermore, only 71 percent of the obese patients presented with tumors less than 2 centimeters as compared to 79 percent in the non-obese group."

Researchers also found that obesity is a significant factor in breast cancer mortality. Obese women are more likely to have higher rates of lymph node metastases and be diagnosed at later cancer stages.

"When looking at survival in the obese population, our study showed a trend towards worse overall survival in these obese patients," said Dr. Haakinson.

The study also found that women in the obese population were less likely to undergo immediate breast reconstruction. Unlike other research, no biological differences in the tumors were found in this study, said Dr. Haakinson.

The results were presented at the Annual Meeting of the American Society of Breast Surgeons at the end of April.

"We feel that breast cancer screening is highly important in the obese population, with regular mammography as well as clinical examination. Obese patients have been shown to have poor outcomes and this is likely a result of a variety of factors," said Dr. Haakinson. "We encourage obese women to engage in regular breast cancer screening and consult with their doctor should they detect any changes in their breast or have breast symptoms that worry them, so that timely diagnosis of breast cancer is made in this high risk population."

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