A simple test could potentially target chemotherapy for breast cancer in only those women most likely to benefit, reports a study in the New England Journal of Medicine.
The study, led by University of Michigan Comprehensive Cancer Center researchers, found that women with the most common form of breast cancer -- in which the tumours are estrogen-receptor positive and HER -2 receptor negative -- were most likely to benefit from adding the drug Taxol to their chemotherapy regimen.
Women whose tumours were estrogen-receptor positive, but did not express HER-2, did not get any benefit from the drug.
As many as three-quarters of breast cancers are estrogen-receptor positive and about 15 per cent to 20 per cent of breast cancers express HER-2, a protein that spurs the growth of breast cancer cells.
The study could one day mean that women with HER-2-positive breast tumours could be spared the toxic side effects of a therapy that may not be effective for them.
"In general, chemotherapy for breast cancer has been a one-size-fits-all approach," says lead study author Dr. Daniel Hayes of the UM Comprehensive Cancer Center. "With this data we hope we will be able to focus chemotherapy on patients whom it's most likely to help."
But the researchers caution they are not recommending a change in treatment at this point. They say more research must be done to confirm that Taxol does not benefit some estrogen-receptor-positive breast cancer.
The study looked at tissue samples and data from 1,500 women who had previously participated in a study looking at the benefit of adding Taxol after four cycles of the drugs Adriamycin and Cytoxan, so-called AC chemotherapy.
Cancer had spread to the lymph nodes in all of the women, which is a standard indication to recommend chemotherapy.
All the women were given AC chemotherapy, after which half the women received four cycles of Taxol and the other half did not receive any more chemotherapy.
The researchers found that the addition of Taxol improved survival rates in women who were HER-2-positive -- regardless of their estrogen receptor status. Women whose tumours were HER-2-negative and estrogen-receptor-positive had no additional benefit from the Taxol. More than half of the patients in the study fell into this category.
"We've seen mortality from breast cancer dropping in recently years because we've applied these new and better therapies. But now we believe, if these results are confirmed and validated in other studies, that perhaps we could pull out half the patients in that study and save them from the toxicities and the cost of receiving a drug that might not do them any good," said Hayes.
"In oncology, we are very good at adding therapies to a patient's regimen, but we are not as confident subtracting treatment," added senior study author Donald Berry, professor and head of the Division of Quantitative Sciences at The University of Texas M. D. Anderson Cancer Center.
"Hopefully, in time, we'll be able to limit therapies to those that will truly benefit from the additional regimen."
