Estrogen-only HRT slightly ups breast cancer risk

Last Updated: 2006-12-25 9:30:21 -0400 (Reuters Health)

NEW YORK (Reuters Health) - In a nationwide study, Finnish researchers found a slightly elevated risk of breast cancer in women who used estrogen-only hormone therapy for 5 years or longer. Use of estrogen for less than 5 years was not associated with breast cancer risk.

Estrogen for 5 years or more, either in pill or patch form "means 2 to 3 extra cases of breast cancer per 1,000 women who are followed for 10 years," Dr. Olavi Ylikorkala from Helsinki University Central Hospital and colleagues report in the December issue of Obstetrics and Gynecology.

The risk of breast cancer was similar with oral and patch (transdermal) estrogen. It's been suggested that patch estrogen may be safer than pill estrogen with regard to risk of breast cancer, "but in our study a transdermal route did not vary from the oral one in this regard," the researchers note.

The findings are based on all Finnish women older than 50 years using estrogen-only therapy for at least 6 months during 1994 and 2001 who were followed for breast cancer until the end of 2002.

In a commentary, Dr. John Collins notes that women suffering hot flashes and other distressing symptoms related to menopause "can be reassured that short-term (less than 5 years) use of either combined estrogen-progestin therapy or estrogen alone will have little appreciable effect on their personal breast cancer risk."

"Longer use of combined estrogen-progestin therapy undeniably increases their breast cancer risk, likely to a greater extent than exposure to estrogen alone," Collins writes. "However, the level of risk remains similar to risks that many women accept through lifestyles that expose them to daily alcohol ingestion, lack of regular exercise, and postmenopausal obesity."

SOURCE: Obstetrics and Gynecology, December 2006.