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Drug halves breast cancer relapse rate for some

October 19, 2005

By Gene Emery

BOSTON (Reuters) – In studies described as “stunning,”
researchers reported on Wednesday that a drug already used to
treat advanced cancer can prevent half of all breast tumors
from reappearing after standard therapy.

But the treatment only works in women whose breast tumors
carry excessive amounts of a protein known as HER2 that makes
the cancer particularly aggressive, and on occasion may cause
serious side effects.

About one in five women with breast cancer have such
tumors, so 42,000 U.S. women could benefit from the treatment.

The drug is trastuzumab, sold under the brand name
Herceptin by Genentech Inc. in the United States and by Swiss
drugmaker Roche in Europe.

Approved in 1998 to treat breast tumors that have spread,
routine use of the drug cuts the recurrence rate by nearly 50
percent, at least over the short term, two new studies in The
New England Journal of Medicine show.

“This is a very important finding. It’s likely to change
the recommended care for patients. But we need to know more
about the side effects and the long-term effectiveness,” said
Richard Gelber of the Dana-Farber Cancer Institute and an
author of one study known as the HERA study.

“The results are simply stunning,” said Gabriel Hortobagyi
of the University of Texas M.D. Anderson Cancer Center in
Houston, who predicted in a Journal editorial that the findings
“will completely alter our approach to the treatment of breast
cancer.”

SIDE EFFECTS

But there are potentially troubling side effects.

Trastuzumab can damage the heart in some women, although
the problems usually fade if the drug is discontinued, Gelber
told Reuters. In addition, women who receive the drug after
breast cancer surgery are more likely to develop subsequent
tumors in the brain or elsewhere in the nervous system.

But in an era when doctors are happy if a drug improves the
survival rate by just a few percentage points, a medicine that
cuts the tumor recurrence rate by nearly 50 percent is
considered a significant improvement.

Only tamoxifen, a mainstay of cancer treatment, produces
such good results, said Hortobagyi. HER2 tumors tend to be
resistant to tamoxifen, said Harold Burstein of Dana-Farber.

Researchers must still determine if trastuzumab would work
even better if given in chemotherapy or for more than a year.

In the HERA study, sponsored by Roche, 3,387 women in 39
countries were given standard surgery and chemotherapy but half
received trastuzumab every three weeks for a year.

A year after treatment ended, doctors found only 127
instances of death, new cases of breast cancer or some other
type of tumor among the trastuzumab recipients compared to 220
such cases among volunteers who did not get the drug.

About 6 percent of the patients stopped taking the drug
because of adverse results. The risk of heart problems was low,
the study said, “but this could change with longer follow-up.”

Results of the second study, actually a combination of two
studies partly funded by Genentech, were released in April by
the U.S. National Institutes of Health. They found a similar
reduction in death or new cancer among women who got
trastuzumab while receiving conventional chemotherapy.

But the rate of heart problems was much higher — 4.1
percent against less than 1 percent in the HERA study.




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