CHICAGO - A drug to prevent bone loss during breast cancer treatment also
substantially cut the risk that the cancer would return, results that left
doctors excited about a possible new way to fight the disease.
It is the first large study to affirm wider anti-cancer hopes for Zometa and
other bone-building drugs called bisphosphonates. Zometa, made by Novartis AG,
is used now for cancers that have already spread to the bone.
The study was led by Dr. Michael Gnant of the Medical University of Vienna and
reported Saturday at an American Society of Clinical Oncology conference in
Chicago.
The study was sponsored by Zometa's maker, Swiss-based Novartis, and
British-based AstraZeneca PLC, which makes Arimidex, the brand name of
anastrozole. Gnant consults for the companies and several other breast cancer
drugmakers.
The new study involved 1,800 premenopausal women taking hormone treatments for
early-stage breast cancer. Zometa cut by one-third the chances that cancer would
recur, in their bones or anywhere else.
"This is an important finding. It may well change practice," said Dr. Claudine
Isaacs, director of the clinical breast cancer program at Georgetown
University's Lombardi Cancer Center.
If a second, ongoing study also finds a benefit, doctors predict that Zometa
will quickly be tested against other cancers that tend to spread, or
metastasize, to bones, such as prostate and kidney cancer.
"Hugely important is whether this has to do with the fact that it just makes the
bone hostile, somehow, to metastasis or if there is a more global
anti-metastasis effect," said the oncology group's president, Dr. Nancy Davidson
of Johns Hopkins University.
"Either of those would be good and would teach us a lot about what to do next."
Breast cancer is the most common cancer in women. About 184,450 cases and 40,930
deaths from the disease are expected in the United States this year.
Standard treatments are surgery, chemotherapy, radiation and hormone-blocking
drugs if the tumours are like those in the study - helped to grow by estrogen or
progesterone.
The hormone-blockers often weaken bones, so bisphosphonates like the
osteoporosis pill Fosamax have become increasingly popular to treat this side
effect. However, using them to treat the cancer itself is a very different
approach.
Lab studies hinted it would work, and Gnant's is the first to test it in a large
group of breast cancer patients.
All had surgery to remove their tumours and were taking hormone-blocking drugs -
goserelin plus either tamoxifen or anastrozole - treatments that made them
menopausal. Half also were given infusions of Zometa once every six months.
The women were treated for three years and studied for two more. By then, only
six per cent of those given Zometa had suffered a relapse or died, compared to
nine per cent of the others. That translated to a 36 per cent decline in risk.
Sixteen women given Zometa died versus 26 of the others - a difference that
could have occurred by chance alone but an encouraging trend that doctors hope
will mean better survival as the groups are followed for a longer time.
There were no big differences in serious side effects, though minor ones like
fever and bone and joint pain were more common among women given Zometa. Two per
cent of all study participants developed a rapid heartbeat, but only three were
hospitalized - two on Zometa and one of the others.
With doctor fees for the infusion, a Zometa treatment can run more than $1,200.
The other large study is testing it in 3,360 pre-and postmenopausal women with
cancer that has spread but not extensively.
Experts stressed that the results so far are only in women who were made
menopausal by hormone-blocking treatments, not women who develop breast cancer
after natural menopause.
For now, using Zometa to prevent breast cancer recurrence should be confined to
those who develop breast cancer before menopause, said Dr. Eric Winer of
Dana-Farber Cancer Center in Boston.
"This is a treatment that doctors should talk to a patient about" because of
these encouraging new results, Winer said.
In other news at the conference, women with advanced breast cancers who were
given Avastin plus Taxotere were a little less likely to have their cancers
progress than women given Taxotere alone. However, side effects including high
blood pressure were more common for those taking both drugs. Taxotere treatment
is more common in Europe and Asia; in the United States, doctors are more likely
to use Taxol.
In the study of 736 women, 44 per cent of those given just Taxotere had their
tumours shrink versus 55 per cent of those also given a lower dose of Avastin
and 63 per cent of those given a higher dose.
Avastin, marketed by California-based Genentech and Swiss-based Roche Holding
AG, recently won federal approval for breast cancer - against the
recommendations of outside advisers. The approval was based on measurements like
those in this study - cancer progression, rather than overall survival. The new
study was too short to show any differences in survival.
