A new use of an old drug may save the lives of younger women with an aggressive type of breast cancer, according to research hailed as a "major breakthrough."

The drug trastuzumab, sold under the name Herceptin, had long been used to lengthen the lives of women with late-stage breast cancer, but it didn't cure them.




But a cancer-fighting conference in Florida heard on Friday that three clinical trials indicate the drug may stop an aggressive form of breast cancer when given early to younger women.

Those women that used the drug in combination with chemotherapy had a 52-per-cent decrease in recurrences compared to those who did not, results from two North American trials said.

In one of the trials, which included Canadian women, researchers found that four years after diagnosis, 33 per cent of women receiving only chemotherapy had a recurrence of their cancer.

Dr. Stephen Chia
Dr. Stephen Chia

For the women who got chemotherapy plus Herceptin, the recurrence rate fell to 15 per cent.

"This is a major advance for many thousands of women with breast cancer," said Dr. Andrew von Eschenbach, director of the U.S. National Cancer Institute, which sponsored the trials.

"This is a major breakthrough in the management of breast cancer," said Dr. Mark Clemons, an oncologist at Toronto's Sunnybrook Hospital.

Drug curbs cancer-fuelling protein

A similar study on a global scale confirmed the findings of the North American trials. Almost 5,100 women were enrolled across 39 countries in the study sponsored by Herceptin's makers, the Swiss company Roche.

The drug works by attacking cancer cells that produce too much of a protein called HER-2. Approximately 20 to 30 per cent of breast cancers have these type of tumours. They grow faster and are more likely to recur than those that don't produce an excess of the protein.

"For women with this type of aggressive breast cancer, the addition of trastuzumab to chemotherapy appears to virtually reverse prognosis from unfavourable to good," said Dr. Edward Romond, lead researcher of the North American trials and professor of oncology at the University of Kentucky.

Most of the 3,300 women in the North American trials had breast cancer that had spread to the lymph nodes. They were given the drug soon after diagnosis and monitored for up to five years.

"On its own it has some activity, but when given with chemotherapy it seems to enhance the benefit of chemotherapy," Dr. Stephen Chia of the B.C. Cancer Agency told CBC News.

Still much to learn about Herceptin

It's estimated that 2,000 women a year in Canada could benefit from the drug.

But It will be months and possibly years before they're offered Herceptin for early breast cancer.

The findings must first be reviewed and published in a peer-reviewed journal, which is required before a new drug strategy gets government approval. Then Health Canada will have to approve the use.

Then there is the cost. A one-year's prescription of Herceptin would cost $40,000, and that would have to be borne by provincial drug plans.

Also, the drug can increase the risk of congestive heart failure.

Chia said there's still a lot to learn about how Herceptin works.

"On its own, it has some activity but when given with chemotherapy, it seems to enhance the benefit of chemotherapy," Chia said.