Results of a study that followed women up to 30 years adds to evidence that silicone breast implants do not boost cancer risk.

The study, of nearly 2,800 Danish women who got breast implants between 1973 and 1995, found that these women actually had a lower risk of breast cancer than a group of similar but implant-free women. Also, the implants were not tied to other types of cancer, according to findings published in the International Journal of Cancer.

Women with breast implants did have a higher rate of non-melanoma skin cancers, the most common and least threatening forms of the disease. But it’s possible that greater sun exposure explains that association, the study authors speculate.

The findings are in line with the conclusions of recent expert review committees, and should reassure women with silicone-gel implants, according to lead study author Dr. Soren Friis of the Danish Cancer Society in Copenhagen.

“There is convincing evidence that breast implants are not associated with an increased risk of breast cancer,” he told Reuters Health.

Past research had indicated that, despite fears about the cancer-causing potential of silicone found in animal studies, silicone breast implants do not lead to cancer in some women. But few studies had looked at breast cancer risk beyond the 15-year mark, or at the risk of tumors in sites other than the breast.

Women in the current study were followed for up to 30 years after receiving breast implants, and overall, their risk of developing breast cancer was 30 percent lower than that of the 1,736 women in the comparison group.

The reason for the lower risk is unclear, according to the researchers.

It’s possible, they speculate, that women who seek breast implants are generally at less risk of breast cancer; in past research, Friis’s team found that compared with other women, those with implants tended to be thinner and have more pregnancies - a factor that has been linked to lower breast cancer risk.

The current study also found no evidence that women with breast implants were diagnosed with breast cancer any later than other women - even though implants can interfere to some degree with the x-rays used in mammography screening.

There are special positioning techniques that improve mammography’s effectiveness for women with breast implants, Friis pointed out. So it’s important, he said, for women to inform their doctors and mammography technicians that they have implants so that they receive the proper technique.

SOURCE: International Journal of Cancer, February 15, 2006.