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Body Mass Index may serve as prognostic tool for advanced, aggressive breast cancers

March 14, 2008

HOUSTON - Body Mass Index (BMI), the measure of a person's fat based on their height and weight, may be an effective prognostic tool for specific types of breast cancer, according to research from The University of Texas M. D. Anderson Cancer Center.

The study, published in the March 15 issue of Cancer Research, reports that women with locally advanced breast cancer (LABC) and inflammatory breast cancer (IBC) with high BMIs had worse prognosis than women with the disease whose BMIs were in the healthy range.

One's BMI is scored based on height and weight. A score less than 18.5 indicates that a person is underweight and a score of 18.5 -24.9 indicates that one is in a normal or healthy range. A person is overweight if their score is 25-29.9 and any score above 30 classifies that a person as obese.

According to Massimo Cristofanilli, M.D., the study's senior author, LABC, or cancer that has spread to nearby tissue or lymph nodes, accounts for approximately five percent of newly diagnosed breast cancer cases each year in the United States. In underserved communities, LABC accounts for 50 percent of new cases. IBC is extremely aggressive, yet rare - representing just 1- 2 percent of all breast cancers diagnosed in this country.

Before now, there were few epidemiological or retrospective studies suggesting a correlation between weight gain, obesity and risk of developing breast cancer; even fewer had address the prognostic value of obesity, said Cristofanilli, associate professor in M. D. Anderson's department of Breast Medical Oncology.

"This is the first study to highlight the value of BMI at the time of diagnosis as a prognostic indicator in women with aggressive disease and at a high risk of recurrence and at the time of diagnosis in locally advanced disease, including it's most aggressive form, inflammatory breast cancer," said Cristofanilli. "We embarked on this research because the vast majority of our newly-diagnosed inflammatory breast cancer patients were overweight or obese, and IBC is associated with a poor prognosis. The idea was to understand the etiological link between the most aggressive forms of breast cancers and, ultimately, with prognosis."

For the retrospective study, researchers reviewed 606 patients - 495 (82 percent) with LABC and 111 (18 percent) with non-metastatic IBC. All were enrolled in clinical protocols at M. D. Anderson between 1974 and 2000. The median follow up was six years for all patients; for women still alive, the median follow-up was 9.9 years.

In calculating BMI, 208 (34 percent) of the patients were normal or underweight, 194 (32 percent) were overweight and 204 (34 percent) were obese. Cristofanilli noted that obesity was more frequent in women with IBC, 45 percent vs. 31 percent in non-IBC cases.

For the entire group, the median overall survival was 8.6 years and recurrence-free survival was 5.8 years. Both statistics were significantly worse for overweight and obese patients compared to those who were of normal weight or underweight.

Specifically regarding overall survival, for overweight LABC patients, five-year survival was 58.3 percent and 10-year survival was 44.1 percent; 58.6 percent of obese LABC patients lived five years and 42.4 percent lived 10 years. In contrast, 69.3 percent of women with LABC who were normal or underweight lived five years and 57.3 percent lived 10 years.

In women with IBC who were overweight, five-year survival was 45.3 percent and 10-year survival was 29.1 percent; 49.3 percent of obese IBC patients lived five years and 43.7 percent lived 10 years. In comparison, 55.1 percent of women with IBC who were normal or underweight lived five years and 50.9 percent lived 10 years.

For the design of the study, it's important to note that all patients received similar anthracycline-based treatments and that doses were not adjusted based on a patient's weight, said Cristofanilli.

"Of course, it's important to explore interventions to prevent overall obesity. These outcomes may have a major impact not only on the incidence of future breast cancer patients, but on their long-term outcome," Cristofanilli said.

"From a research standpoint, we really need to further look at the relationship between obesity and some endocrine factors that may explain why inflammatory breast cancer patients are more frequently obese, for example. Our next step is to go back to the lab and start looking into those specific factors related to obesity in breast cancer - insulin, estrogen levels and leptin are areas of immediate interest."

Cristofanilli acknowledged that dietary intervention might be difficult for women undergoing chemotherapy; however, some change of lifestyle habits for overweight and obese patients after diagnosis are vital.

Cristofanilli noted that before BMI is completely accepted as a prognostic tool for breast cancer, prospective trials and endocrinology studies must be conducted. However, to oncologists currently treating overweight and obese LABC and IBC patients, Cristofanilli recommends they be more aggressive in follow-up, including considering more frequent physical exams and imaging studies.

University of Texas M. D. Anderson Cancer Center