Obesity Worsens Prognosis for Some Breast Cancer Patients

The obesity epidemic has continued at an increasing rate in both adults and children.  There are some obese and overweight individuals who have no metabolic derangements and carry no additional health risks due to their weight.  These people are very few and are part of a small minority of individuals.  For the vast majority of people who are overweight or obese, the extra weight has negative health consequences and increases the risk of type 2 diabetes, high blood pressure, abnormal lipid parameters, heart disease, and stroke.  Overweight and obesity has also been associated with increased risk of some forms of cancers.

Researchers, led by Dr. Joseph Sparano of the Albert Einstein College of Medicine, have found that being overweight or obese at the time of diagnosis for hormone receptor positive breast cancer patients worsens the overall prognosis.  The results of their research were published online in the journal Cancer.  The researchers studied the associated between weight and prognosis in breast cancer for 6,885 women enrolled in U.S. National Cancer Institute clinical trials.  The women had stage 1 to 3 breast cancer with excellent performance status and normal cardiac, renal, hepatic, and bone marrow function so that the effect of confounding variables could be decreased.  The researchers found that obesity at the time of diagnosis for estrogen or progesterone hormone receptor positive breast cancer was associated with a 30 percent higher risk of recurrence and almost 50 percent higher risk of death even with optimal treatment.

The authors wrote, “We evaluated the relation between BMI and clinical outcomes in a cohort of 6885 women with stage I to III breast cancer enrolled in 3 clinical trials that included adjuvant doxorubicin-containing chemotherapy. Similar to previous individual reports and a meta-analysis of these other reports, we found that obese patients, defined as having a BMI of 30 kg/m2 or higher, exhibited a significantly higher risk of recurrence and death. This is likewise consistent with a population-based study that demonstrated inferior outcomes for obese patients”.

The authors also wrote, “…analysis of the E1199 dataset is the first report to demonstrate that worse outcomes are observed specifically in women with hormone receptor-positive/HER-2–negative disease who were treated with contemporary chemoendocrine therapy (including anthracyclines, taxanes, and aromatase inhibitors) but not other breast cancer subtypes. Furthermore, there was a continuous relation between increasing BMI and inferior outcomes in this specific subtype, indicating that excessive weight may also be a surrogate for other factors contributing to recurrence not only in obese but also in overweight patients”.

The authors concluded, “The results of this analysis clearly establish a relation between higher BMI at the time of breast cancer diagnosis and higher risk of recurrence and death, specifically in hormone receptor-positive, HER-2–negative disease, which accounts for about 2/3 of all breast cancers. What remains uncertain, however, is whether dietary and lifestyle interventions resulting in weight loss after a breast cancer diagnosis could substantially reduce the risk of recurrence, and also perhaps provide secondary benefits in reducing cardiovascular morbidity and mortality”.

This is an important study because it corroborates previous results that have shown an association between overweight and obesity and worse prognosis in breast cancer.  This study adds new information in that it identifies estrogen and progesterone hormone receptor positive breast cancers and not the other subtypes as the ones that carry the poorer prognosis.  The exact mechanism for this is currently unclear but may be related to the fact the adipose tissue produces estrogen which may stimulate the breast cancer cells excessively.  This will need to be confirmed in future studies.  In addition, future studies will have to determine if weight loss for overweight and obese women will improve the prognosis to the level of normal weight breast cancer patients with the hormone receptor positive disease.

Reference:

Joseph A. Sparano et al. “Obesity at diagnosis is associated with inferior outcomes in hormone receptor-positive operable breast cancer” Cancer first published online August 27, 2012 doi: 10.1002/cncr.27527

Tagged as: BMI, body mass index, breast cancer, Dr. Joseph Sparano, estrogen hormone receptor, obesity, obesity epidemic, progesterone hormone receptor