The results are in and clear - taking a pill a day for five years can slash the risk of breast cancer. But high-risk women are still reluctant to do it.
The cancer specialists who have been comparing the drugs raloxifene and tamoxifen updated findings, showing that tamoxifen lowers the risk of breast cancer in high-risk women by 50%, compared with 38% for raloxifene.
Overall, both drugs saved lives, they told the American Association for Cancer Research meeting.
"I think we need to reassess why we are not using these drugs more broadly and why we are not prepared to reduce the risk of breast cancer by more than 50% in women who are high risk," said Dr Gabriel Hortobagyi of the University of Texas M.D. Anderson Cancer Centre in Houston.
"These drugs are inexpensive with side-effects that are modest."
Side-effects scare women
Five years of either pill costs around $8,500, compared with $50,000 to more than $200,000 for chemotherapy to treat breast cancer, said Hortobagyi.
But it is the side-effects that have scared women away from the drugs. Tamoxifen raises the risk of blood clots, of uterine cancer and of cataracts.
"The way this came out some 15 years ago is that tamoxifen increased background risk for endometrial cancer about three-fold and that scared the hell out of just about anybody," said Hortobagyi.
But he said the absolute risks are very low -- a tripling of an extremely rare cancer like uterine cancer still gives a woman a risk of less than 1% -- compared with a risk of 4% for breast cancer in a given five-year period for the women taking part in the trial.
"People don't understand how small the risks are," said Dr Judy Garber of Boston's Dana-Farber Cancer Institute. For women with a high risk of breast cancer who have not yet reached menopause, the risks from tamoxifen are "minuscule," she said.
Now that the trial shows raloxifene has even fewer risks, and almost the same efficacy, Garber said she would recommend it to older women.
Docs need to be 'won over'
"Tamoxifen in pre-menopausal women is really a no-brainer," said Dr Scott Lippman, also of M.D. Anderson.
The group to win over, the cancer experts agreed, are the primary care physicians and obstetrician/gynaecologists. They will be the ones counseling women on their breast cancer risk.
"In the same way they are discussing a pap smear or a mammogram, they need to be discussing these options with their patients," Hortobagyi told a news conference at the meeting.
Breast cancer is the No. 2 killer of women in the United States after lung cancer, with 40,000 deaths a year. Globally, it kills more than 460 000 people a year.
"The number of people dying of breast cancer is unacceptable," Lippman said.
What the researhc shows
About two-thirds of breast cancer cases are called oestrogen receptor positive, meaning they are fueled by oestrogen. Both tamoxifen and raloxifene are selective estrogen receptor modulators, or SERMs, and interfere with oestrogen.
Both tamoxifen, sold by AstraZeneca under the brand name Nolvadex, and raloxifene, sold by Eli Lilly and Co under the brand name Evista, were originally designed to treat cancer.
Research found tamoxifen could reduce the risk that a woman who had cancer in one breast would have it come back in the other.
Then tests showed tamoxifen could prevent cancer for women at high risk because they had mothers or sisters with the disease, they had a history of suspicious looking breast lumps or they had a precancerous condition called ductal carcinoma in situ.
"The risks were zip in comparison to the benefits to me," said Martha Smith of Grand Rapids, Michigan, who took both drugs and who has not developed breast cancer, a disease that killed her mother and sister. - (Reuters, April 2010)