An international study found that many women did just as well after breast cancer surgery by taking only estrogen-blocking tamoxifen pills, which do not cause the hair loss, nausea and other side effects of chemotherapy.
"Some women can go straight to tamoxifen," Richard Gelber, a biostatistician at the Dana-Farber Cancer Institute and Harvard Medical School in Boston who worked on the study, said in a telephone interview.
But Gelber stressed that this study, published in the Journal of the National Cancer Institute, applies to a limited group of women.
"We are speaking exclusively about postmenopausal women with lymph-node negative tumors ... (meaning) they haven't spread," he said. "It would be a big mistake to extrapolate this to to node-positive (when the cancer has spread to the lymph nodes) and pre-menopausal women."
And the 25 percent of women whose cancer is "estrogen-receptor negative" -- not affected by the hormone estrogen -- survive longer with chemotherapy.
Studies are underway to see if women who have not entered menopause, and those whose cancer has spread, may be able to do without chemotherapy, as well.
The researchers said it is clear that women need more individually tailored therapy than they get now.
Dr. Andrew D. Seidman, a breast cancer specialist at Memorial Sloan-Kettering Cancer Center in New York City, said the study "will reaffirm the way that many oncologists are now practicing" and should help doctors base cancer therapies on the specific characteristics of their patients.
A team of researchers from nine countries compiled the study. The study was limited to breast cancer surgery patients who had completed menopause and whose disease had not spread to the lymph nodes. About 43 percent of the approximately 184,000 women in the United States diagnosed with breast cancer each year fit this category, the study said.
Researchers further divided the 1,669 patients in the study into groups based on whether their cancers were sensitive or not sensitive to estrogen, a hormone that can promote the growth of breast cancer cells.
There were 382 in the study whose tumors were not sensitive to estrogen, described in medical terms as being estrogen receptor negative, or ER-negative. There were 1,217 who were ER-positive.
About half in each of these groups were treated with chemotherapy followed by five years of tamoxifen. The other half of each group received tamoxifen only.
Researchers followed the patients for an average of almost six years and found the value of chemotherapy depended directly on the estrogen sensitivity of the patients' disease.
Among the ER-positive patients, chemotherapy provided no benefit. The five-year, disease-free survival for those who only took tamoxifen was 85 percent, while it was 84 percent for those who had both chemo and tamoxifen.
However, for the ER-negative patients, chemotherapy could be a life saver. The five-year, disease-free survival for those who had both chemo and tamoxifen was 84 percent. But for ER-negative patients who took only tamoxifen, the survival rate was only 69 percent, a 15 percentage point difference.
Gelber said the study may improve the lives of patients who are ER-positive because it will ensure they don't have to endure chemotherapy's side effects, such as hair loss, nausea and persistent tiredness.
"There is a quality of life burden associated with chemotherapy," said Gelber. "It is not a free ride. It should not be given frivolously."
On the other hand, he said, the study showed that chemo's side effects were not severe enough that it should be avoided by the ER-negative patients who would benefit.
Gelber said a quality-of-life segment of the study showed the side effects from chemo are usually temporary and go away after the therapy ends.
Dr. Monica Castiglione-Gertsch, who leads the International Breast Cancer Study Group from Bern, Switzerland, said there is a growing trend among doctors to offer women whose cancer has not spread the option of taking tamoxifen alone.
The study joins several that say breast cancer treatments need to be carefully tailored.
In May, researchers told the annual meeting of the American Society of Clinical Oncology that studies clearly showed when tamoxifen and chemotherapy are both given to a patient, the tamoxifen should only be taken after chemotherapy is complete. Otherwise it interferes with the effectiveness of the drugs.