The committee reviewed recent studies which had investigated aromatase inhibitors and/or tamoxifen in women with this particular subtype of breast cancer.
Using an aromatase inhibitor alone or with tamoxifen therapy improved disease-free survival compared with using tamoxifen alone. It also reduced the risk of the cancer spreading to other parts of the body.
Women who are pre- or peri-menopausal when they are diagnosed should be given tamoxifen for five years. Aromatase inhibitors are not effective in this age group, the experts note.
All three aromatase inhibitors on the market - Arimidex (anastrozole), Femara (letrozole) and Aromasin (exemestane) - were essentially equal in their benefit.
The drugs can also cause side effects that need to be taken into account when prescribing.
"We've learned a huge amount about the various side effect profiles of these products," said Dr. Harold J. Burstein, co-chair of the ASCO committee which prepared the guidelines and associate professor of medicine at Harvard Medical School and Dana-Farber Cancer Institute in Boston. "Aromatase inhibitors are clearly associated with osteoporosis and with bone and joint [conditions]. They might also be associated with a greater risk of hypertension and high cholesterol."
For its part, tamoxifen is also associated with serious side effects, which can include cataracts and uterine cancer as well as life-threatening blood clots and stroke.
And cost will also be a factor in decision-making.
"Aromatase inhibitors are very expensive. And sometimes we have to make decisions about using drugs that are probably a little less effective but at the same time we have to take into account the financial
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