Postmenopausal women with early breast cancer who take tamoxifen for five years appear to have a 30 percent lower risk of dying from coronary heart disease than women who remain on the drug for just two years, Swedish researchers report.

The results come from an extended follow-up of 4175 women who participated in the landmark tamoxifen study by the Swedish Breast Cancer Group. Those study findings were originally reported in1996, showing that tamoxifen reduces the recurrence rate of breast cancer.

Dr. Bo Nordenskjold, head of the Oncology Centre for Southeast Sweden, and co-investigators found that among the women who took tamoxifen for two years, 381 women died from causes other than breast cancer over following years; that compared with only 307 non-breast cancer deaths in the group that took tamoxifen for five years.

At a press briefing Monday at the European Society of Medical Oncology Congress, Nordenskjold said the major difference was in cardiovascular mortality and specifically in deaths from coronary heart disease.

In the two-year group, 163 women died from cardiovascular disease, compared with 136 women in the five-year group. In the 2-year arm, 78 women died from coronary heart disease compared to 54 women in the 5-year arm.

The effect on coronary heart disease, however, is delayed.

“This difference in mortality in coronary heart disease is a late event,” Nordenskjold said. “The first 7 or 8 years you see no difference. But the difference emerges gradually.”