Breast-feeding linked to lower risk of endometrial cancer

An analysis of 17 past studies suggests that while breast-feeding for any period of time appears to lower a woman’s risk of endometrial cancer, mothers who breast-fed for the recommended six months lowered their risk even further.

Surpassing the 6-9 month recommended timeframe for breast-feeding seemed to have little benefit, the researchers said, but those who had ever breast-fed their children were 11 percent less likely than women who had children but didn’t breast-feed to be diagnosed with endometrial cancer, Reuters reported.

“Cancer of the uterus is becoming more common and we need to try to prevent it,” lead author Susan Jordan, of the QIMR Berghofer Medical Research Institute in Brisbane, Australia, told Reuters. “The more women know about the things they can do to reduce their risks of future cancer diagnosis, the better.”

For the report, which was published in Obstetrics and Gynecology, researchers used data compiled in the Epidemiology of Endometrial Cancer Consortium, including 10 from the United States and others from Canada, China, Europe and Austrialia, Reuters reported. They looked at more than 26,000 women who had ever had a child, whether they breast-fed, and for how long. Among the women, researchers discovered about 9,000 had been diagnosed with endometrial cancer.

After accounting for other factors that can influence endometrial cancer risk, including age, race, education, oral contraceptive use, menopausal status, years since last pregnancy and body mass index (BMI), researchers found the apparent protective effect of breastfeeding remained.

Notably, the risk reduction linked to breastfeeding was 28 percent among women born after 1950, but negligible among those born before 1950, which may reflect differences in breastfeeding practices, they study authors note. In the United States in the 1950s and 1960s, for example, breastfeeding rates were much lower than in recent decades, the authors note.

The study doesn’t prove that breastfeeding helps to protect against endometrial cancer, but it’s plausible, the authors write, because the growth of this type of cancer is stimulated by estrogen, which is suppressed during breastfeeding,” says Dr Jordan.

“We can’t say that this is definitely a causal relationship. However, it is plausible that breastfeeding could directly reduce the risk by suppressing ovulation and reducing estrogen levels, and in turn reducing cell division in the lining of the uterus.

“It is important to point out that breastfeeding won’t guarantee that a woman won’t develop cancer of the uterus, and, conversely, not breastfeeding doesn’t mean a woman will get uterine cancer.

“However, this study strongly suggests that breastfeeding reduces a woman’s risk. It’s already well known that breast feeding has lots of great benefits for mums and their babies. This is just one more benefit to add to the list.

“For a whole range of reasons, some women are either unable to breastfeed, or struggle with breastfeeding. While it’s important not to put more pressure on these women, this study suggests that supporting women to breastfeed could help reduce the incidence of uterine cancer.”

The study involved collaborators from the United States, Europe and China.