ABC3: Higher Insulin Is an Independent Prognostic Factor in Advanced Breast Cancer


Key Points

  • 46.95% of the patients in the study were classified as insulin-resistant, 40.5% were overweight, and 16.37% were obese (BMI > 30).
  • Progression-free survival was around 11.5 months in those with a HOMA score of less than 2.5 and 8.5 months in those with a score of 2.5 and over.
  • Researchers cited better diet, increasing exercise, and using drugs like metformin as ways to combat insulin resistance but added that more trials are needed to define effective treatment strategies.

Patients with metastatic breast cancer who have higher insulin levels than normal, but are not diabetic, have a significantly worse prognosis compared with those who have normal insulin levels, according to data being presented (Abstract BP129) at the Advanced Breast Cancer Third International Consensus Conference on November 6, 2015, in Lisbon, Portugal.

Although the effect of higher insulin levels is already known in patients with early breast cancer, this is the first time that insulin resistance—where the body’s inefficient use of insulin leads to the production of an excess—has been shown to lead to a worse outcome for patients with metastatic breast cancer.

Nicoletta Provinciali, MD, an oncologist from the E.O. Ospedali Galliera, Genoa, Italy, will describe to the conference her team’s study, which involved 125 metastatic breast cancer patients. In addition to not being diabetic, all those involved had HER2-negative tumors and were receiving first-line chemotherapy as part of a clinical trial. The researchers assessed the relationship between insulin resistance, progression-free survival, and overall survival.

“After taking into account other factors likely to affect [progression-free survival] and [overall survival] in these patients, such as age and body mass index (BMI), we found that higher insulin levels were an independent factor leading to a worse prognosis in patients with advanced breast cancer,” said Dr. Provinciali.

Study Details

The researchers measured glucose levels in the patients using the HOMA index, a mathematical formula to assess individual levels of insulin sensitivity. A normal range is around 2; patients with a score of 2.5 or above are likely to have insulin resistance. Overall, 46.95% of the patients were classified as insulin resistant, 40.5% were overweight, and 16.37% were obese, with a BMI of more than 30.

Of the 125 women involved who had a median age of around 60 years, progression-free survival was around 11.5 months in those with a HOMA score of less than 2.5 and 8.5 months in those with a score of 2.5 and over.

“We found clear evidence that insulin resistance is associated with a significantly worse prognosis for metastatic breast cancer patients and that metabolic status influences this prognosis. We need to consider ways of targeting this metabolism in order to give these patients a better chance,” said Dr. Provinciali.

“We know that growth factors are critical to cancer development and progression. We know that insulin is an important growth factor for all body tissues, even if we do not know exactly how it affects the development of cancer cells,” said Dr. Provinciali.

Ways of tackling the problem could include adopting simple lifestyle changes such as a better diet and more exercise as well as the use of inexpensive and widely available drugs such as metformin, said the researchers. More awareness of the effect of insulin resistance on cancer progression among clinicians is also needed.

“Although we know that higher insulin levels adversely affect prognosis in cancer patients and is an independent risk factor in several types of cancer—for example, specific organ sites such as the pancreas, liver, and endometrium—the evidence is still quite recent and needs to be better known by clinicians and even oncologists. We also need more trials to better define effective treatment strategies for these patients,” said Dr. Provinciali.

“We would now like to see a trial evaluating the effect of physical activity and diet on individual patient metabolism. We believe that all patients with advanced breast cancer should be counseled on the potential effect of these kinds of lifestyle changes,” Dr. Provinciali concluded.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.