ORLANDO, Fla., May 19 (UPI) -- Doctors reported Sunday that tamoxifen, the tried-and-true drug used to prevent breast cancer recurrence, still should be considered treatment of choice -- despite emergence of newer drugs that appear to be superior.
The report -- released by the American Society of Clinical Oncology at its annual meeting -- suggested the newer drugs known as aromatase inhibitors appear do not yet have the long-term track record of tamoxifen.
Therefore, the committee assessing the new data in those clinical trials declined to change its recommendations at this time.
"The panel was influenced by the compelling, extensive and long-term data available on tamoxifen," said Dr. Eric Winer, director of the Breast Oncology Center at the Dana-Farber Cancer Institute, Boston, Mass. "Patients and physicians can rest assured that tamoxifen remains the best option for use outside of clinical trials, and that it reduces the risk of recurrence and improves overall survival with manageable side effects for most women."
Dr. Larry Norton, professor of medicine at the Weill Medical College of Cornell University in Ithaca, N.Y., and president of ASCO, said, "We accepted this report with great enthusiasm."
The report was triggered by recent clinical studies suggesting better outcomes were possible with anastrozole, a member of a group of drugs that inhibit or prevent the production of estrogen, the hormone associated with breast cancer progression and recurrence in some patients.
The aromatase inhibitors anastrozole, letrozole and exemestane -- technically an aromatase inactivator -- are recommended for use in patients who already have cancer that has spread. "We think that all the aromatase inhibitors are reasonable agents in metastatic breast cancer," Winer said.
He said his panel recommended a technology assessment that followed review of the data in recent trials. But, he said, the recommendations are not etched in stone. He said in two to three years enough data on long-term use of the aromatase inhibitors will be available for the doctors to review their position.
"One of the critical points in the decision," said Dr. William Gradishar, professor of medicine at Northwestern University School of Medicine, Chicago, Ill., "is that we have learned that tamoxifen doesn't reach its optimal effect until five years of use. Very few patients on aromatase inhibitors have been on the drug that long. We think that with the passage of time we will be able to make recommendations with greater confidence."
However, Gradishar told United Press International if a patient were put on an aromatase inhibitor to prevent cancer recurrence, it would not indicate doctor error. He noted there are small groups of patients who would not be good candidates for tamoxifen -- including those with a history of blood clots and other relatively rare conditions.
Dr. Paul Goss, director of the Breast Cancer Prevention Program at Princess Margaret Hospital, and professor of medicine at the University of Toronto, Canada, said he believes "these recommendations are too cautious."
Goss said, "We really won't know for sure if the aromatase inhibitors are as good as tamoxifen for 15 years," and suggested most of the evidence for decades has suggested that limiting estrogen production has benefit in preventing breast cancer.
"We can assume that the aromatase inhibitors are going to be at least as good as tamoxifen," Goss told UPI, "and we also know that small numbers of women can have serious side effects from tamoxifen use -- endometrial cancer and formation of blood clots. We haven't seen those side effects in women on these drugs yet."
Goss also said in addition to human studies with the aromatase inhibitors, extensive pre-clinical trials have not found these side efects.
"Shifting clinical practice always takes a leap of faith whenever you do it," said Goss, suggesting now is an appropriate time to make that change and move from tamxoifen to aromatase inhbitors.
In another presentation at a press briefing Sunday, doctors said that physicians should make changes in how anticancer drugs are delivered to breast cancer patients:
-- Dr. Jean-Marc Nabholtz, professor of medicine at the University of California at Los Angeles, said that by replacing the drug 5-fluorouracil with docetaxel in a combination treatment for breast cancer, patients could experience a 32 percent decrease in the risk of cancer recurring.
-- Dr. Kathy Albain, professor of medicine at Loyola University, Chicago, said it appears that the order in which drugs are given makes a difference in outcome as well. She found an 18 percent improvement in staying free from recurrent breast cancer if a patient starts tamoxifen treatment after completing chemotherapy rather than taking tamoxifen along with the other treatments.