In 1997, two randomized trials, the HABITS ( Hormonal Replacement Therapy-Is It Safe ? ) trial and the Stockholm trial, began in Sweden to test the effects of menopausal hormone therapy in women after they had been diagnosed with early-stage breast cancer.
The HABITS trial, which included 434 breast cancer patients, was halted early in December 2003 because, at a median follow-up of only 2.1 years, the risk of breast cancer recurrence among women receiving hormone therapy was 3.3 times higher than the risk among women receiving no treatment.
Much of the design of both studies was similar; however, a goal of the Stockholm protocol, not shared with the HABITS trial, was to minimize the use of progestogen combined with estrogen.
In the Stockholm trial, 378 breast cancer patients were randomly assigned to receive either menopausal hormone therapy for 5 years or no treatment.
At a median follow-up of 4.1 years, the risk of breast cancer recurrence was not associated with menopausal hormone therapy ( relative hazard, RH = 0.82 ).
According to Authors, doses of estrogen and progestogen and treatment regimens for menopausal hormone therapy may be associated with the recurrence of breast cancer.
Source: Journal of National Cancer Institute, 2005