Breast cancer drug switch cuts deaths-study

By Lisa Richwine

ATLANTA (Reuters) – Switching to Pfizer Inc.’s drug
Aromasin after a few years on another breast cancer treatment
cut some women’s risk of dying from the disease by 17 percent
in a study released on Saturday.

Researchers looked at more than 4,700 women past menopause
who had been treated for early stage breast cancer and were
disease-free after two to three years of taking the drug
tamoxifen to prevent a recurrence.

About half were randomly chosen to substitute Aromasin,
while the other half continued on tamoxifen. Total treatment
lasted five years.

Scientists tracked their progress for about 2.5 years after
treatment stopped.

They found that women who switched to Aromasin had a 17
percent lower risk of dying from the disease than others who
took only tamoxifen. There were 210 deaths in the Aromasin
group and 251 in the tamoxifen group.

The findings, presented at the annual meeting of the
American Society of Clinical Oncology, applied to women with
what is known as hormone-sensitive breast cancer. It is the
latest study to compare the benefits of the two types of drugs.

“Worldwide there are still thousands of women taking
tamoxifen, and you could immediately affect their chances of
survival by switching to Aromasin,” Dr. Stephen Jones, one of
the study researchers and medical director for U.S. Oncology
Research, said in an interview.

Tamoxifen — long the drug of choice for preventing breast
cancer — blocks estrogen, which can help fuel the growth of
tumors in some cases.

Aromasin, known generically as exemestane, and similar
drugs inhibit the enzyme aromatase, which is needed to produce
estrogen. The aromatase inhibitors are now being used just
after breast cancer surgery instead of tamoxifen in many women
to keep the disease from returning. Both are taken orally.

In the new study, side effects from the drugs differed.
Women who took only tamoxifen had higher rates of blood clots,
uterine cancer and vaginal bleeding. Aromasin patients had
slightly more fractures, a known risk from aromatase
inhibitors.

A separate study showed women treated for five years with
AstraZeneca Plc’s aromatase inhibitor Arimidex lost about 6
percent of bone in the spine and 7 percent in the hips. That
was about twice what would be expected in women in the study,
who were age 64 on average.

None of the patients with normal bone density at the start
of therapy lost enough bone mass to be diagnosed with
osteoporosis, which can increase fracture risk, said Dr. Robert
Coleman, a medical oncologist at Weston Park Hospital in
Sheffield, England.

Women taking Arimidex should have their bone density
monitored every one to two years and take calcium and vitamin D
supplements, Coleman said.

Tamoxifen was sold by AstraZeneca Plc under the name
Nolvadex but now is marketed by several generic drug makers.