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One study found that certain women did better - were less likely to die or have a relapse - if given a less harsh drug than Adriamycin, a mainstay of treatment for decades.
Another study found that a gene test can help predict whether some women need chemo at all - even among those whose cancer has spread to their lymph nodes, which typically brings full treatment now.
The findings are sure to speed the growing trend away from chemo for many breast cancer patients and targeting it to a smaller group of women who truly need it, doctors said at the San Antonio Breast Cancer Symposium, where the studies were reported.
New test will change practice
"We are backing off on chemotherapy and using chemotherapy more selectively" in certain women, said Dr Eric Winer of the Dana-Farber Cancer Institute in Boston.
The gene test in particular "will start changing practice nearly immediately," said D. Peter Ravdin of the University of Texas M.D.
Anderson Cancer Centre in Houston. "The results are compelling that this test helps select patients who will most benefit from chemotherapy."
Breast cancer is the most common major cancer in American women.
More than 178,000 new cases are expected this year. Most are helped to grow by oestrogen, and hormone-blocking medicines like tamoxifen are used to treat those.
Chemo no effect on some
Here is where Oncotype DX, a test that measures the activity of 21 genes and gives a score to predict a woman's risk of recurrence, comes in. Doctors have used it for several years to guide treatment for certain women with early breast cancers, especially those that have not spread.
The new study, led by Dr Kathy Albain of Loyola University in Chicago, looked at whether it accurately predicted chemo's benefit in 367 women whose hormone-driven cancer had spread to lymph nodes.
A decade after these women were treated, those who had low scores on the gene test were found to have had no benefit from chemo. Conversely, chemo did a lot of good for those with high scores.
Because 40 percent of the women scored low, it means that as many as 18,000 women each year might safely skip chemo.
Test is expensive
Dr Kelly Marcom, a Duke University cancer expert said the test would give valuable information to guide treatment for more patients in the future. He has used it on about 50 women in the last year.
"I've had it cut both ways" - ruling chemo in and out, Marcom said.
The test is expensive - $3,400 (about R23 000) - though many US insurers are paying for it because it can avoid even more costly chemo.
These new studies should lead to less use of chemo, but there has been "intense" resistance from doctors, who fear giving up on a treatment that might help some patients, said Barbara Brenner, head of the advocacy group Breast Cancer Action.
"It's very hard to turn a ship like this," she said. "Adding things never takes much, but removing things takes a mountain of data from the medical community." – (Sapa/AP)
December 2007
