Women with diabetes have a slightly higher risk of developing breast cancer than women without diabetes. Most of the studies have looked at people with type 2 diabetes, simply because more people have type 2 diabetes than type 1. Type 2 diabetes tends to develop as you get older and your are more likely to get it if you are overweight or obese.
The research into weight and breast cancer are complicated but it looks like being obese increases your risk of developing breast cancer after you’ve had the menopause (post-menopausal breast cancer).
| Age | Risk of developing breast cancer if you DON’T have diabetes | Risk of developing breast cancer if you DO have diabetes |
| Up to 30 years | 0.05 % | 0.06 % |
| Up to 40 years | 0.5 % | 0.6 % |
| Up to 50 years | 2 % | 2.4 % |
| Up to 60 years | 4 % | 4.9 % |
| Lifetime risk | 11 % | 13.6 % |
How were these numbers calculated? A 2007 study that pooled the results of 20 different studies into diabetes and the risk of breast cancer identified a 1.24 relative risk. This means that people with diabetes have a slightly increased risk of developing breast cancer.
What does a 1.24 risk mean in actual numbers? Well your risk of breast cancer increases as you get older, you can see the statistics on this page on “Breast Cancer Risk Factors” from the Breast Cancer Campaign.
| Age | Risk as a ratio | Risk as a Percentage |
| Up to 30 | 1 in 1,900 | 1 divided by 1900= 0.00052 x100 = 0.05 % |
| Up to 40 | 1 in 200 | 1 divided by 200 = 0.005 x 100 = 0.5 % |
| Up to 50 | 1 in 50 | 1 divided by 50 = 0.02 x 100 = 2 % |
| Up to 60 | 1 in 23 | 1 divided by 23 = 0.043 x 100 = 4% |
| Life time risk | 1 in 9 | 1 divided by 9 = 0.11 x 100 =11% |
These are the risks for a person without diabetes, but a relative risk of 1.24 means you are at more risk, so you need to work out the percentage risk plus 0.24, so as an example, your lifetime risk without diabetes is 11 %, so 11×24=264. 264 divided by 100 =2.64 %. So someone with diabetes has the normal risk (11 %) plus the diabetes risk (2.64%) which added together means a person with diabetes has a 13.6 % risk of developing breast cancer assuming they live into their eighties.
Remember of course these numbers are averages and so they apply to big groups of people and not to individuals. No one can know exactly what will happen to them. This also means that over 85 % of people with diabetes will NOT develop breast cancer in their lifetime.
Why is this interesting? A study out today showed that a drug used to treat diabetes, metformin (also called glucophage or fortamet) could help treat breast cancer. When the researchers used both metformin and the chemotherapy drug doxorubicin together they were able to kill cancer cells both in mice and in a dish in the lab. It has also been reported that people with diabetes receiving metformin have lower incidence of cancer (New users of metformin are at low risk of incident cancer), this research was carried out by scientists at Dundee University.
So what does this mean if you have diabetes?
You should be aware that diabetes may slightly increase your risk of breast cancer, if you notice anything unusual about your breasts, including any lumps your should tell your GP (even if it is embarrassing). It is possible that some of your diabetes medicines may lower your risk of cancer, so it is important to have good control.
What does this mean if you have breast cancer?
The study out today was done in mice and cells in a lab dish, there are now plans by the Canadian Institute of Health to carry out a clinical trial in humans. This study is just experimental and doesn’t change the standard treatments for breast cancer. However, if the trials in humans are successful it is likely that the treatment will be available more quickly than most new drugs, because metformin has already been approved for use (and shown to be safe) in humans.
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[...] in Laboratory Research by Avril Sep 18 2009 TrackBack Address. This week I wrote a post on diabetes and breast cancer (September 16th 2009), where I mentioned that the diabetes drug metformin, also known as Glucopahge [...]
the standard for diabetes is Metformin but i also try to use alternative medicine in controlling diabetes. Alpha Lipoic Acid and Charantia seems to work well too against diabetes.
Metformin has been scientifically proven to treat diabetes (http://www.cks.nhs.uk/diabetes_type_2/evidence/supporting_evidence/hypoglycaemic_drugs/metformin).
Herbal remedies are a great starting point for further research but they should not be used to treat diabetes on their own. Diabetes UK does not reccommend the use of any herbal supplement (http://www.diabetes.org.uk/Guide-to-diabetes/Treatment__your_health/Treatments/Complementary_therapies/Herbal_supplements/)
Diabetes today is mostly caused by a lifestyle that has less exercise and too much sugar. Diabetes can be easily avoided by just doing simple exercises each day like jogging and avoiding sugars. If you already have diabetes, exercise is still the best way to manage it. Food supplements like Charantia and Chromium also helps.
Some types of type 2 diabetes are caused by lifestyle factors. Some but not all, some types of type 2 diabetes are genetic and are not related to a lack of excercise or a poor diet. Type 1 diabetes can not be avoided by excercise or diet, neither can it be treated by Chranatia or Chromium, it can only be treated by regular injections of insulin.