In-depth study unveils complex impact of obesity and metabolic syndrome on breast cancer risk

Recent research led by a University of Oklahoma academic has identified nuanced relationships between obesity, metabolic syndrome, and breast cancer risks, potentially guiding better preventative strategies for at-risk patients. The comprehensive findings stem from the Women’s Health Initiative (WHI), an extensive study initiated in the early 1990s focused on postmenopausal women’s health issues, including cancer, cardiovascular diseases, and osteoporosis.

Robert Wild, M.D., Ph.D., a professor of obstetrics and gynaecology at the OU College of Medicine, and a longstanding contributor to the WHI, co-authored this pivotal study published in the journal Cancer of the American Cancer Society. This investigation is part of a series of outputs from the WHI, which remains the largest preventative health study on women. It builds on previous research which demonstrated that a low-fat diet could reduce breast cancer mortality by 21% over two decades, prompting further exploration into whether this benefit was due to reduced obesity levels or amelioration of metabolic syndrome symptoms.

Dr. Wild elaborated on the study’s findings, stating, “This study shows that obesity had an effect on breast cancer independent of metabolic syndrome, and that metabolic syndrome had an effect on breast cancer independent of obesity. And they affected various subtypes in different ways, which influenced whether women were diagnosed with breast cancer and whether they died from it.”

The study’s insights are multifaceted: it confirms the importance of managing both body weight and metabolic health to mitigate breast cancer risks. Dr. Wild emphasised the foundational health practices, remarking, “This study is essentially saying to get back to the basics. Prevention is important, and we need to be paying attention to both metabolic syndrome and weight.” Metabolic syndrome comprises a cluster of conditions—elevated blood pressure, high blood sugar, excess abdominal fat, and abnormal cholesterol or triglyceride levels—all of which also heighten the risk of cardiovascular disease and diabetes.

In more detailed findings, the study reported:

• Metabolic syndrome is significantly associated with a 53% increase in deaths post-breast cancer diagnosis and a 44% rise in breast cancer mortality rates.
• The syndrome adversely affects prognosis specifically in cases of oestrogen receptor (ER)-positive and progesterone receptor (PR)-negative breast cancers.
• ER-positive cancers, which constitute 70-80% of all breast cancer cases, are typically hormone-dependent for growth and generally respond to hormone therapy.
• Conversely, PR-negative cancers lack hormone receptors, do not benefit from hormone therapies, and often exhibit faster growth compared to hormone-positive cancers.
  

The research also highlighted obesity’s impact, noting a higher incidence of breast cancer and mortality rates particularly among women with severe obesity. However, obesity showed a correlation with better outcomes in ER-positive and PR-positive cancers, which are treatable with hormone therapy and generally have a slower growth rate.

Dr. Wild reflected on the lasting value of the WHI data, saying, “The Women’s Health Initiative is the gift that keeps on giving. It is a great opportunity to make use of quality information. In the beginning, I don’t think we knew what a valuable resource it would still be years later.”

This study not only underscores the complex interactions between obesity, metabolic syndrome, and breast cancer but also reinforces the critical need for integrated health strategies to address these risks comprehensively.