Breastfeeding & Breast Cancer

It seems logical that these topics should be related, but is there really a link between breast cancer risk and breast-feeding? Many studies seem to say that there is. There are plenty of questions and some very powerful answers available in the literature.

Does breast-feeding have any effect on my risk of developing cancer?

Does breast-feeding have any effect on the baby's risk of developing cancer?

Does it make any difference how long I breast-feed?

Is it true that some women develop masses in their breast due to breast-feeding?

 

Does breast-feeding have any effect on my risk of developing cancer?
There are many studies -- most of which contradict one another -- on whether breast-feeding cuts your risk of breast cancer.

In a recent study published in the journal Cancer, researchers compared the lactation histories of 446 South African women with breast carcinoma with those of 1,471 women admitted to hospitals with conditions unrelated to breast cancer. The study found no connection between breast cancer risk and the number of children breast fed, the length of time mothers breast fed, or the mother's age at first lactation.

The December 1997 issue of the American Journal of Epidemiology provides a study involving 1,313 women which showed that premenopausal women had a 50 percent lower risk of breast cancer if they had breast-fed for at least 20 months, compared to women who had at least one baby and had not breast-fed.

In the July 1999 issue of the American Journal of Epidemiology a study found that women who had breast fed for a little as two weeks showed a reduced risk of breast cancer up to 50 years later.

Another study recently reported in the International Journal of Epidemiology followed two groups of women from North Carolina. The study compared 751 women diagnosed with breast cancer, and 742 who didn't have it. Of those who had cancer, 310, or 41.3 percent, had breast-fed. Of those who didn't have cancer, 356, or 47.9 percent had breast-fed -- leading to a 30 percent reduced chance of breast cancer if you breast-fed. Studies like this make me shake my head in wonder. The results are valid. There really is a 30% lower risk of being in the breast cancer group if you breast fed, but 41.3 percent of the cancer group had breast fed... what happened to their reduced risk?

The conclusion is that taken with all of the various genetic and environmental factors that influence a women's risk of developing breast cancer - breast feeding certainly does not increase the risk -- and long term breast feeding may, in fact, reduce the risk of developing breast cancer.

One warning for women who have been diagnosed with breast cancer is that breast-feeding seems to increase the speed at which a tumor grows. Some advocates of breast-feeding recommend breast-feeding anyway. The bulk of the professional literature tends to discourage breast-feeding for women who have breast cancer or who have had breast cancer.

Does breast feeding have any effect on the baby's risk of developing cancer?
A 1988 article in the Lancet showed that children who are artificially fed or breast fed for only 6 months or less, are at an increased risk of developing cancer before age 15. The cancer risk of bottle-fed children was 1-8 times that of children who had been breast fed for longer than 6 months. The risk for babies breast fed for a shorter time was 1-9 times that of long-term breast feeders.

Epidemiology and Medicine & Pediatric Oncology have both featured studies that show a 25% lower risk of developing breast cancer for women who were breast fed instead of bottle-fed as infants, even if only for a short time. This effect was true for both premenopausal and postmenopausal breast cancer.

Does it make any difference how long I breast feed?
In the American Journal of Epidemiology (1996) a study of Mexican women associated less time breast feeding with increased breast cancer risk.

A study recently published in the International Journal of Epidemiology counters the findings of previous studies that the longer you breast-fed, the more you cut your breast-cancer risk. This study found a 30 percent reduction in breast cancer risk for women who had breast fed their babies for any amount of time. The author stated, "Breast cells become more mature once they've undergone their natural function; the breast is carrying out the function it was made to do."

A Chinese study showing an inverse relation between length of breast-feeding and breast cancer revealed that the women breast-fed on average for three years. In June 1998 Newsweek reported that only 38% of American moms even try breastfeeding and only 15% nurse for one year. This is one of the lowest rates in the world. The American Academy of Pediatrics and the American Dietetic Association urge mothers to nurse for at least 12 months.

Other theories for the causes of breast cancer include the strong role of ovarian hormones, estrogen and progesterone. A study in the British Journal of Cancer reported that the number of children breast-fed did not decreased the risk of breast cancer, but longer total duration of breast-feeding provided a stronger protective effect.

Breast-feeding delays the onset of ovulation after pregnancy, thus reducing a woman's overall exposure to the hormone. It would be logical that longer breast-feeding, which depresses hormone levels for longer periods of time, would be more effective in preventing breast cancer.

Is it true that some women develop masses in their breast due to breast feeding?
The answer to this one is yes. A small percentage of nursing mothers develop obstructions in the milk ducts known as "galactoceles." They can occur while you are nursing, but appear more commonly after lactation has stopped, when the milk is allowed to stay in the breast.

A breast self exam may reveal smooth, movable, sometimes tender masses. These may well be localized collections of milk, but should be followed up on by your doctor.

Your doctor may recommend aspiration which will both diagnose and cure the condition. Fluid milk is removed when the aspiration is performed during or soon after lactation. If the lesions are older and it has been a while since you stopped nursing the milk may have become a thicker, cheesy material. Several aspirations may be necessary to completely drain the duct. Ice packs and a well-fitting support bra are helpful.

Mammography is not usually necessary. Galactoceles may be difficult to distinguish from other fat-containing breast lesions on mammography. There is a characteristic mammographic appearance which may show layering of fat density over water density.

There is no known relationship between galactoceles and fibrocystic breast disease. Surgery is rarely required.
 

also see -> Breastfeeding & Breast Cancer Risk

Are You At Risk For Breast Cancer?