Obesity and insulin: a predictor of breast cancer

Obesity and insulin are associated with an increased risk of recurrence and death in women with breast cancer, according to research presented today at the Leura V International Breast Cancer Conference, hosted by the NSW Breast Cancer Institute in Darling Harbour, Sydney.

Professor Pamela Goodwin from the Mount Sinai Hospital, University of Toronta, Canada, reported that previous clinical studies have demonstrated an increased breast cancer risk in premenopausal women with higher insulin levels. In an extension of this work, more than 50 studies have examined the association of insulin as a strong new predictor of recurrence and death in women with breast cancer.Weight gain has been reported to occur after breast cancer diagnosis, particularly in women receiving chemotherapy and in those who become menopausal. Large amounts of weight gain (over 10 kg) have been associated with worse outcomes.Professor Goodwin reported that recent research had focused on mechanisms by which obesity and weight gain may impact breast cancer outcomes. Most commonly cited potential mechanisms include more advanced tumour stage in obese women, chemotherapy underdosing, elevated levels of estradiol (a female sex hormone), reduced levels of sex hormone binding globulin, direct effects of diet and, more recently, elevated levels of members of the insulin/IGF family of growth factors.Since 1989, Professor Goodwin and her colleagues have been studying these issues in more than 500 women with newly diagnosed breast cancer, focusing primarily on obesity and related factors.”We’ve found that women who are overweight at breast cancer diagnosis are more likely to develop recurrences and die, and they have shown that high insulin levels arising from obesity probably act as growth factors to stimulate breast cancer in these women.”The research has also shown that obesity is associated with reduced levels of physical activity, high calorie/high fat diets, altered coping styles, psychological distress and reduced quality of life – all of which could be targets for future interventions to help women with breast cancer lose weight and improve their outcomes.Professor Goodwin concluded that the implications of the findings are that a group of women with a markedly increased risk of recurrence and death have been identified in whom new treatment strategies should be explored.”These strategies could include the exploration of more aggressive treatment using standard chemotherapeutic agents, the development of novel agents that target insulin receptor interaction or signalling pathways, or development of approaches such as exercise, weight loss or insulin sensitisers that lower insulin levels by enhancing insulin sensitivity.”(Source: Leura V International Breast Cancer Conference: MedEdge: November 2004.)