Study Examines Link Between Breast Cancer and Diabetes12/13/12
THURSDAY, Dec. 13 (HealthDay News) -- Postmenopausal breast
cancer survivors are at increased risk for developing diabetes and
should be screened for the disease more closely, a new study
Researchers analyzed data from 1996 to 2008 from the province of
Ontario, Canada, to determine the incidence of diabetes among
nearly 25,000 breast cancer survivors aged 55 or older and nearly
125,000 age-matched women without breast cancer.
During a median follow-up of more than five years, nearly 10
percent of all the women in the study developed diabetes. Compared
to those who had not had breast cancer, the risk of diabetes among
breast cancer survivors was 7 percent higher two years after cancer
diagnosis and 21 percent higher 10 years after cancer diagnosis,
the investigators found.
The risk of diabetes, however, decreased over time among breast
cancer survivors who had undergone chemotherapy. Their risk
compared to women without breast cancer was 24 percent higher in
the first two years after cancer diagnosis and 8 percent higher 10
years after cancer diagnosis, according to the study, which was
published Dec. 12 in the journal
"It is possible that chemotherapy treatment may bring out diabetes earlier in susceptible women," study author Dr. Lorraine Lipscombe, of Women's College Hospital and Women's College Research Institute in Toronto, said in a journal news release. "Increased weight gain has been noted [after receiving] chemotherapy for breast cancer, which may be a factor in the increased risk of diabetes in women receiving treatment."
"Estrogen suppression as a result of chemotherapy may also promote diabetes," Lipscombe added. "However, this may have been less of a factor in this study where most women were already postmenopausal."
The study authors suggested that there may be other factors
involved for women who received chemotherapy, including
glucocorticoid drugs, which are used to treat nausea in patients
receiving chemo and are known to cause spikes in blood sugar. In
addition, breast cancer patients undergoing chemotherapy are
monitored more closely and thus are more likely to have diabetes
detected, they noted.
The researchers said it is unclear why diabetes risk increased
over time among breast cancer survivors who did not receive
"There is, however, evidence of an association between diabetes and cancer, which may be due to risk factors common to both conditions," Lipscombe said. "One such risk factor is insulin resistance, which predisposes to both diabetes and many types of cancer -- initially insulin resistance is associated with high insulin levels and there is evidence that high circulating insulin may increase the risk of cancer."
"However, diabetes only occurs many years later when insulin levels start to decline," she said. "Therefore, it is possible that cancer risk occurs much earlier than diabetes in insulin-resistant individuals, when insulin levels are high."
Overall, the "findings support a need for closer monitoring of
diabetes among breast cancer survivors," Lipscombe concluded.
Although the study found an association between diabetes and
breast cancer, it did not prove a cause-and-effect
American Cancer Societyoutlines what happens
after breast cancer treatment.
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