Hormone-producing enzyme inhibitor cuts risk of breast cancer relapse

Scientists have found that aromatase inhibitor letrozole prevents breast cancer recurrences and reduces the risk of death in post-menopausal women with hormone receptor-positive early breast cancer.

Results from the longest-running trial comparing tamoxifen with the aromatase inhibitor letrozole found that if women with early breast cancer were given letrozole after surgery for at least five years, they continued to do better and have fewer recurrences of the disease than those who were given tamoxifen.

“Over a median of eight years of follow-up, women who were assigned to receive five years of letrozole after surgery had an 18 per cent reduced risk of relapse and a 21 per cent reduced risk of death compared with those assigned to receive tamoxifen,” said Professor Richard Gelber, Director of the International Breast Cancer Study Group (IBCSG) Statistical and Data Management Centre at the Dana-Farber Cancer Institute, Boston, MA, USA.

Tamoxifen has been the “gold standard” hormone treatment for women with early, oestrogen-receptor-positive breast cancer and works by blocking the growth-promoting action of oestrogen on the cancer cells.

Aromatase inhibitors, such as letrozole, are newer and alter the function of aromatase, an enzyme involved in oestrogen production.

They can be used in sequence with, or as an alternative to tamoxifen for post-menopausal women.

In the BIG 1-98 trial, researchers enrolled 8,010 patients to receive letrozole and tamoxifen either alone or in sequence, with a total of 4,922 patients included in the monotherapy arms of the study.

This 12-year update shows that, among all 8,010 patients, there were 2,074 relapses and 1,284 deaths, compared with 1,569 relapses and 923 deaths at the ten-year update.

“The data also show that the sequential use of letrozole and tamoxifen (two years of one agent followed by three years of the other) provided similar outcomes compared with five years of letrozole alone for patients who are not at high risk for recurrence,” said Prof Gelber.

The study was presented at the 2011 European Multidisciplinary Cancer Congress, in Stockholm.