Are breast cancer patients more at risk of developing diabetes?

by Barbara Hewitt on December 24, 2012

Are breast cancer patients more at risk of developing diabetes?

Women who survive breast cancer are more likely to develop diabetes and should be screened more closely, especially if they have undergone chemotherapy, according to scientists in Canada. Researchers now believe that the association between diabetes and cancer is becoming increasingly recognised – for example, women with diabetes have an estimated 20% higher risk of developing postmenopausal breast cancer.

While historically little research has been carried out on the long term health consequences for those who have had breast cancer, researchers have now looked at the relationship between the two in more detail. The study, which is the largest to explore this relationship, has found that post-menopausal survivors of breast cancer are more likely to develop diabetes when compared against a control group without breast cancer. It has also found that the relationship between breast cancer and diabetes varies depending on whether a breast cancer survivor has undergone chemotherapy.

Dr Lorraine Lipscombe of the Women’s College Research Institute, in Toronto, used population based data from Ontario, Canada to compare the incidence of diabetes among women aged 55 years or older with breast cancer, from 1996 to 2008, with that of age matched women without breast cancer. The research team found that, of 24,976 breast cancer survivors and 124,880 controls, 9.7% developed diabetes over a mean follow up of 5.8 years. The risk of diabetes among breast cancer survivors compared with women without breast cancer began to increase two years after diagnosis, with a 7% increased risk that rose to 21% after 10 years.

Among those who received adjuvant chemotherapy, which was 4,404 patients, almost the opposite relationship was found. Risk was highest in the first two years after diagnosis, a 24% increased risk compared with controls, and then declined to an 8% increased 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,’ said Dr Lipscombe.

Quote from DiabetesForum.com : “This hit me hard because my first wife of 28 years died of colon cancer in 1994. All the old feelings came back and bless her heart my wife was very encouraging about this go around. She knows how this has affected me but I have to be strong for her too. So hand and hand we will walk this journey. Thanks for letting me unload.”

‘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 post-menopausal,’ she explained. Other factors that may play a part are the glucocorticoid drugs used to treat nausea in chemotherapy, known to cause spikes in blood sugar and the fact that women undergoing chemotherapy could be monitored more closely and thus are more likely to have diabetes detected.

She also pointed out that a reason that risk decreased in the chemotherapy group over time could be that many of the at-risk women developed diabetes in the first two years, and were thus no longer followed up – in addition, the effects of glucocorticoids are known to wear off over time. The researchers are unsure why the breast cancer survivors who did not receive chemotherapy saw their risk of diabetes increase compared with control women without cancer.

‘There is, however, evidence of an association between diabetes and cancer, which may be due to risk factors common to both conditions. These findings support a need for closer monitoring of diabetes among breast cancer survivors,’ added Dr Lipscombe.


The opinions expressed in this article do not necessarily reflect the views of the DiabetesForum.com Community and should not be interpreted as medical advice. Please see your doctor before making any changes to your diabetes management plan.

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