A new class of breast cancer drug that women can take after the standard five years of tamoxifen therapy saves lives as well as preventing the return of tumors, according to Canadian researchers last week.

Femara, made by Swiss drugmaker Novartis, reduced the risk of death by 39 per cent in women who took it, compared with women who took a placebo.

It reduced the spread of cancer (metastasis) by 40 per cent, they told a meeting of the American Society of Clinical Oncology.

The findings add to the evidence that the drugs, called aromatase inhibitors, are a valuable extra weapon in the arsenal against breast cancer, which will affect 1.2 million people globally this year.

For the study, Dr. Paul Goss, from Princess Margaret Hospital in Toronto, has been studying 5,100 women who took the standard treatment, tamoxifen, for five years.

Tamoxifen cuts the risk of breast cancer in half and greatly reduces the risk that it will come back in women who have already had one bout with the disease.

But the hormone-based therapy stops working after five years and can have adverse effects. Doctors have been testing the aromatase inhibitors to see if adding them to the treatment regime after the five years of tamoxifen will help even more.

Goss and his colleagues reported last year that Femara, known generically as letrozole, reduced even further the risk that breast cancer would return in women who took it after tamoxifen.

"We in fact did reduce internal metastases, which are inevitably fatal," Goss said.

"We also reduced the risk of dying. We have a survival advantage for women taking this drug."

Among women taking Femara, 28 died of breast cancer during the study. Among women taking the placebo, 45 died. Goss noted that some women took Femara for longer than others did.

The women took the drug for a median of two-and-a-half years.

Goss said the drug seemed safe, except that Femara seems to increase the risk of the bone-thinning disease osteoporosis .

"There is an apparent slight increase in bone loss," he said. "A slightly increased number of women developed osteoporosis during the trial. But there was no difference in fractures. At least we know about it and it is easy to fix and prevent."

Goss said 8 per cent of the women taking Femara developed osteoporosis, compared with 6 per cent of women on placebo.

"There will be some women in whom cancer is such a low risk and whose risk of osteoporosis is so high that this drug might not be suitable," Goss added.

Another drug in the same class is Arimidex, made by AstraZeneca and known generically as anastrozole.

The aromatase inhibitors work through a different mechanism from tamoxifen, perhaps offering an advantage. Both reduce the effects of estrogen, a hormone that can fuel tumor growth.

Novartis is trying to distinguish Femara from Arimidex and has filed for the drug to be used by post-menopausal women who have completed standard therapy in North America, the European Union and Switzerland.

(Agencies via Xinhua June 22, 2004)