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Breast cancer survivors more likely to develop diabetes: study

December 12, 2012 Toronto

Postmenopausal survivors of breast cancer are more likely to develop diabetes than women without breast cancer according to researchers at the Institute for Clinical Evaluative Sciences (ICES) and Women’s College Research Institute (WCRI).

“The relationship between breast cancer and diabetes varies depending on whether a breast cancer survivor has undergone chemotherapy,” says Dr. Lorraine Lipscombe, a scientist with ICES and Women’s College Research Institute.

An association between diabetes and cancer is becoming increasingly recognized. For instance, women with diabetes have an estimated 20 per cent higher risk of postmenopausal breast cancer and up to a 50 per cent increase in mortality after breast cancer diagnosis.

The population-based study examined the incidence of diabetes among women in Ontario aged 55 years or older with breast cancer from 1996 to 2008 to that of age-matched women without breast cancer and found that:

  • Of 24,976 breast cancer survivors and 124,880 controls, 9.7 per cent developed diabetes over a mean follow-up of 5.8 years.
  • The risk of diabetes among breast cancer survivors compared to women without breast cancer began to increase two years after diagnosis, with a 7 per cent increased risk that rose to 21 per cent after 10 years.
  • Among those who received adjuvant chemotherapy (4,404 patients) almost the opposite relationship was found: risk was highest in the first two years after diagnosis (a 24 per cent increased risk compared with controls) and then declined to 8 per cent inc reased risk after 10 years.

“It is possible that chemotherapy treatment may bring out diabetes earlier in susceptible women. Increased weight gain has been noted in the setting for adjuvant chemotherapy for breast cancer, which may be a factor in the increased risk of diabetes in women receiving treatment. Oestrogen suppression as a result of chemotherapy may also promote diabetes, however this may have been less of a factor in this study where most women were already postmenopausal,” says Dr. Lipscombe.

Authors: L.L. Lipscombe, W.W. Chan, L.Yun, P.C. Austin, G.M. Anderson, P.A. Rochon.

The study “Incidence of diabetes among postmenopausal breast cancer survivors,” is published in Diabetologia, the journal of the European Association for the Study of Diabetes.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.

Women’s College Research Institute (WCRI), part of Women’s College Hospital (WCH), is dedicated to developing medical insights that enhance the health of women and improve health-care options for all. Fully affiliated with the University of Toronto, WCRI scientists lead research that translates into better clinical care that impacts people in Toronto, across Canada and around the world. For more information about how Women’s College Research Institute is transforming patient care, visit Women’s College Research Institute website.

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