Breastfeeding reduces risk of invasive breast cancer

Breastfeeding may offer broad protection against breast cancer that extends to women who delay having children, according to a study released this week.

Previous studies have shown that giving birth before age 25 and having many children protects against certain types of breast cancers, while delayed childbirth is associated with a higher risk of breast cancer.

The most important finding of the new study is that breastfeeding seems to lower the risk of developing breast cancer that comes from having children later in life, said Giske Ursin, associate professor of preventive medicine at the University of Southern California medical school and the study's lead author.

Results of the study were announced at the annual meeting of the American Association for Cancer Research in Los Angeles.

"As more women may choose to delay pregnancy until after 25, it is important to note that breastfeeding provides protection against both oestrogen and progesterone receptor positive and negative tumours," Dr Ursin said.

Women who develop breast cancer that is hormone receptor negative have a much poorer prognosis than women with other types of breast cancer.

The researchers analysed data for women aged 55 and older - including 995 invasive breast cancer patients - and found that breastfeeding appears to have a protective effect regardless of when they started giving birth.

This is important since having many children was only protective among women who began having children at an early age, Dr Ursin said.

"Evidence suggests that women who have children after age 25 can reduce their risk of breast cancer by choosing to breastfeed," Dr Ursin says.