Obesity and diabetes have adverse effects on cancer outcomes

Both obesity and diabetes have adverse effects on outcomes in breast cancer patients who receive chemotherapy as primary treatment before surgery (neoadjuvant chemotherapy), according to research to be presented at the 9th European Breast Cancer Conference (EBCC-9) tomorrow (Friday). Although a high body mass index (BMI) is known to have a negative impact on cancer development and prognosis, until now there has been uncertainty as to whether having a high BMI had an equal effect on patients with different types of breast tumours.

Dr Caterina Fontanella, MD, a trainee in medical oncology from the University of Udine (Italy) and a research fellow with the German Breast Group, based in Neu-Isenburg, near Frankfurt am Main (Germany), will present an analysis based on nearly 11,000 patients with early breast cancer treated with neoadjuvant chemotherapy. She will show that a high BMI adversely affects the chances of surviving without the breast cancer recurring or spreading to other parts of the body, , although this detriment was not seen in those women had been diagnosed with HER2-positive disease.

"Although the overall survival of patients with metastatic breast cancer has increased over the past few decades, it remains an incurable disease," Dr Fontanella will say. "So preventing disease relapse after primary treatment of early breast cancer is fundamentally important in oncology daily practice. Considering that about one-third of the worldwide population has a body mass index higher than 25 kg/m², investigating the possible higher risk of relapse that affects overweight and obese patients compared with normal weight patients should be a priority."

The researchers studied data from 8,872 early breast cancer patients from the German Breast Group, and 1,855 from a joint EORTC/BIG[1] trial. All had received a modern treatment consisting of an anthracycline/taxane-based neoadjuvant chemotherapy, anti-HER-2 drugs, or hormone therapy according to tumour type and national guidelines.

The vast majority of the patients in this study received chemotherapy doses capped at a body surface area (BSA) of 2.0m², which is often the limit when calculating doses. "Obese patients may have a BSA of more 2.0m², but the chemotherapy dose they receive will not reflect this. It is a very common practice in these patients for fear of overdosing, but of course it means that they will often receive a relatively lower quantity of chemotherapy," Dr Fontanella will say. "In my opinion, a deeper understanding of chemotherapy metabolism and distribution in patients with high BMI and with increased adipose tissue is needed."

"We already know that obese hormone receptor-positive tumour patients respond less well to aromatase inhibitors as adjuvant treatment, and this underlines a key role of higher aromatase activity in patients with increased adipose tissue." Aromatase is an enzyme that synthesises oestrogen, and blocking it is important in cancers where oestrogen encourages tumours to grow.