By Amy Norton, Medical Tribune News Service
ATLANTA -- A year after the breast-cancer treatment tamoxifen
was approved for breast-cancer prevention, further research has
confirmed that the drug cuts some women's cancer risk, but it
remains unclear just who should take it.
In
fact, researchers reported here Tuesday that the tamoxifen decision
ultimately depends on a woman's ``perception of her risk.''
The
Food and Drug Administration approved tamoxifen for breast-cancer
risk reduction in women 35 and older who carry the same cancer
risk as a 60-year-old woman -- that is, a 1.7-percent-or-greater
chance of developing breast cancer within five years.
The
limited evidence of the drug's ability to slash this risk is strong
enough to justify offering it to the 29 million American women
who are candidates, according to Dr. Rowan T Chlebowski, a cancer
specialist at the University of California in Los Angeles.
Under
the direction of the American Society of Clinical Oncology (ASCO),
Chlebowski led a review of all research to date on tamoxifen's
risk-cutting potential. He presented his team's conclusions at
ASCO's annual meeting.
Despite
the positive findings on tamoxifen, for many women who are candidates,
it's unclear whether the drug's benefits outweigh its risks, which
include a more than two-fold increased risk for endometrial cancer
after two years and a doubling in stroke risk among women 50 and
older.
Used
since 1978 to treat advanced breast cancer, tamoxifen entered
the world of risk-reduction under a cloud of controversy. The
drug's approval for its new use was based on a U.S. trial of more
than 13,000 women at increased risk for breast cancer that showed
tamoxifen lowered their risk from 2.6 percent to 1.3 percent --
a relative reduction of 49 percent. A British study of a similar
group of women, however, showed tamoxifen carried no such benefit.
However,
after looking at data from all clinical trials on tamoxifen between
1990 to 1998, the ASCO panel concluded that most research confirms
the tamoxifen benefit and recommended that doctors at least discuss
the drug with higher-risk women. Chlebowski noted that tamoxifen
also provides a small amount of protection against bone loss and
it seems to help lower cholesterol -- although there's no evidence
that it can ward off heart disease.
In a separate study, Boston Medical Center researchers found that
besides cutting breast-cancer risk, tamoxifen may benefit women
who have benign growths that may turn into cancer. Among more
than 2,000 women with pre-cancerous growths, those treated with
tamoxifen were far less likely than those on a placebo pill to
develop cancer. Tamoxifen cut cancer risk by 66 percent, Dr. Donald
Wickerham reported.
There
are still many questions about tamoxifen, the researchers admitted.
Deborah
Collyar, president of the breast-cancer patient advocacy group
Patient Advocates in Research, said that the recommendation to
offer the drug to women at a 1.7-percent risk for cancer may change
since so many women fall into this group. ``Many doctors and advocates
think that [risk percentage] is too low,'' said Collyar, who helped
develop the ASCO report.
The
ASCO group also examined studies on the osteoporosis drug raloxifene,
which has garnered attention for its potential to cut breast-cancer
risk. It concluded that there is too little data to support the
drug's use in this capacity. Only 62 women, Chlebowski said, have
been treated with raloxifene for cancer-risk reduction.
