Hormone replacement therapy link found.(progestin linked to breast cancer)

2003 JAN 2 - (NewsRx.com & NewsRx.net) -- There is more evidence that progestin included in hormone replacement therapy (HRT) is linked to breast cancer.

Postmenopausal women taking combined formulas of hormone replacement therapy that include both estrogen and progestin are at increased risk for lobular breast cancer and new findings further clarify the risks to women who take hormone replacement therapy.

The results from this multicenter study, led by Janet Daling, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, indicate that a specific formula of hormone replacement therapy called combined estrogen and progestin hormone replacement therapy (CHRT) is linked to an increased risk of breast cancer, specifically the less aggressive lobular type of breast cancer.

In women who used CHRT for 5 years or more, those who used the continuous formula that includes progestin daily dosing for more than 25 days per month were at greater risk than those who used the sequential formula with fewer than 25 days per month of progestin daily dosing. There was no association of any type of breast cancer with women who use or used estrogen-only hormone replacement therapy (ERT).

Breast cancer is categorized into several different types, including the most common types, lobular and ductal of which lobular has the better prognosis. Other less frequent categories include papillary, tubular, mucinous and medullary. While the incidence of ductal carcinoma has remained steady since the 1980s, lobular breast cancer rates have increased. HRT comes in two forms, ERT and CHRT. CHRT further comes in various forms, differing, for example, by doses of progestin taken per month.

A few studies have suggested that CHRT, in increasing use since the mid-1980s, may be related to the rising incidence of lobular breast cancer. Moreover, few studies have investigated the relationship between specific types of hormone replacement therapy and specific histological types of breast cancer.

In a large, multicenter, case-control study called the Women's Contraceptive and Reproductive Experiences (CARE) Study, Daling et al. assessed the relationship between types of postmenopausal hormone therapy and histological types of breast cancer.