In a study of more than 24,000 women who underwent breast augmentation in the 1970s and 1980s, Canadian researchers found that the women had a 43 percent lower rate of breast cancer compared with the general population. They also showed a lower-than-average risk of developing cancer of any kind.

The findings, published in the International Journal of Cancer, echo those of past studies showing that silicone-gel implants do not appear to be a cancer risk.

A recent study of Danish women followed for up to 30 years found no evidence of a higher risk of any cancer among implant recipients.

And like that study, the current one also found that women with implants had a lower risk of breast cancer than those who underwent other types of cosmetic surgery in years past.

The reasons for this are unclear, according to the study authors, led by Dr. Jacques Brisson of Laval University in Quebec.

One possibility, they speculate, is that women whose family history puts them at risk of breast cancer are less likely to get cosmetic implants.

Other studies have found that, compared with the general population, women who undergo breast augmentation tend to be thinner and have children at a younger age, both of which may lower the risk of breast cancer.

The current findings are based on data for 24,558 women who underwent breast augmentation, mostly with silicone-gel implants, between 1974 and 1989. Their cancer incidence was compared with that of the general population, as well as a group of 15,893 women who underwent other cosmetic procedures during the same time period.

Women in both cosmetic-surgery groups had lower-than-average rates of both breast cancer and cancer in general, with implant recipients showing the lowest breast cancer rate.

Still, Brisson's team notes, women with implants typically had the procedure around the age of 30, which means they will need to be followed for decades to see whether their breast cancer risk does eventually rise - particularly after menopause.

SOURCE: International Journal of Cancer, June 1, 2006.