Linked to Breast Cancer, Study Finds
NY Times, 12/7/2017
When I saw this headline, I was curious and skeptical. Birth control pills have been around for over fifty years. They have been studied many times and they are associated with slight or no increase in breast cancer. They have the benefit of reducing endometriosis, endometrial cancer and ovarian cancer. They give women control over their reproductive lives. Mostly, the benefits outweigh the risks. What do they mean “STILL” linked to breast cancer? Any linkage to breast cancer has been weak at most.
The study was done in Denmark where everyone is part of the national health service. So basically the whole population is the study group. Novo Nordisk, a drug company, conducted the study.
The study indicated that for every 100,000 women not on birth control, 55 women per year were diagnosed with breast cancer. For every 100,000 women using birth control, 68 women were diagnosed annually with breast cancer. Women who had used Progestin Implants and the Mirena IUD had the same numbers as the women who took oral contraceptives.
The article stated that the longer a woman is on the birth control, the higher the risk of her developing breast cancer. It has been known for decades that women who have more children and breastfeed have lower risks of becoming diagnosed with breast cancer. I suspect women who take contraception for many years probably experience fewer pregnancies, births and breastfeeding. These small differences could simply be due to women having fewer babies and not based on the contraceptive method itself. In studies conducted in the 1960s, Irish nuns had higher rates of breast cancer than Irish women who had many children. I am assuming the nuns were not on birth control.
Another issue supporting this idea is that the results were the same for all of the birth control methods used. If synthetic hormones were the problem, the results should have varied with different methods and doses. The implants and IUD are progestin only, with no estrogen. The IUDs have only a tiny amount of progestin which acts on the uterus directly. I have tested the hormone levels of many women on the Mirena IUD and concluded that the IUD had minimal effect on the woman’s own hormone production.
Women with estrogen/progesterone receptor positive breast cancers have only a 15% mortality rate. 85% never die of their breast cancer. This means that any additional number of women actually dying of breast cancer would be quite small. Some women also die from pregnancy complications. If women become frightened of using these birth control methods, they are at an increased risk of the consequences for any unintended babies or undesired pregnancies.
Just because there is a “statistically” significant difference between two groups does not mean that the difference is meaningful for the women involved. If you buy two lottery tickets instead of one, it is true that you double the opportunity to win. But if that means you go from one chance in a billion to two chances in a billion, your odds haven’t changed in a meaningful way.
Novo Nordisk is a global healthcare company that focuses on diabetes care. Why did they fund this study? Is there some marketing reason why they want to frighten women away from using contraception?
I am not arguing with statistics or the numbers in the study. I just find the conclusions and suggested actions to be questionable.