Osteoporosis drug equals tamoxifen in preventing breast cancer

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One of the largest breast cancer prevention trials ever conducted has found that an osteoporosis drug was as good as tamoxifen at preventing breast cancer among high-risk, postmenopausal women.

John Beale, Post-Gazette
STAR participant Toni Bednar, whose 34-year-old daughter was diagnosed with breast cancer -- "I never really thought too much about [breast cancer] until it hit me between the eyes. I decided if there was anything I could do to eradicate this plague, I was going to do it."
Click photo for larger image.

Initial results of the "Study of Tamoxifen and Raloxifene," or STAR, indicate that like tamoxifen, raloxifene reduced breast cancer risk by about 50 percent, said researchers with the Pittsburgh-based National Surgical Adjuvant Breast and Bowel Project, which coordinated the trial.

Also, participants who took raloxifene, which is currently used to prevent and treat the thin-bone condition called osteoporosis, had 36 percent fewer uterine cancers and 29 percent fewer blood clots than those who took tamoxifen.

"We've declared raloxifene the winner," said Dr. Lawrence Wickerham, the NSABP's associate chairman and a specialist at Allegheny General Hospital's breast cancer center. The study was sponsored by the National Cancer Institute.

The researchers expect that doctors and patients will more readily embrace the drug for breast cancer prevention because it has fewer side effects than tamoxifen.

Toni Bednar, now 66, of Eighty Four, became a STAR participant in January 1999, just after her daughter, a 34-year-old mother of two, was diagnosed with breast cancer.

"I never really thought too much about [breast cancer] until it hit me between the eyes," Mrs. Bednar said. "I decided if there was anything I could do to eradicate this plague, I was going to do it."

So she and more than 19,000 other postmenopausal women who were at high risk of developing breast cancer were randomly assigned to take either tamoxifen or raloxifene daily for five years. They were assessed every six months while taking medication, and annually after that.

There were 167 breast cancers diagnosed among the 9,745 women in the raloxifene group and 163 in the 9,726 women in the tamoxifen group. Among the participants who had not had a hysterectomy, 23 of 4,712 raloxifene users and 36 of 4,732 tamoxifen users developed uterine cancer.

The raloxifene group had a 29 percent lower risk than the tamoxifen group of getting blood clots in a major vein or in the lungs. There was no difference in the occurrence of strokes or stroke mortality.

Mrs. Bednar hasn't yet been told whether she took raloxifene or tamoxifen, although she suspects the latter. Given the study findings, she feels safer, and would encourage others to participate in clinical trials.

"You feel so powerless," she said. "When you do something like this, you feel there's some power given back to you."

Seven years after diagnosis, Mrs. Bednar's daughter is well.

Women in STAR who have not yet completed five years of medication will be given the option of switching to raloxifene if they weren't on it already, said Dr. Victor Vogel, protocol chairman for STAR and director of Magee-Womens Hospital breast cancer prevention program.

Tamoxifen is still the drug of choice for women who have not gone through menopause and have a high breast cancer risk. In that group, the drug does increase the risk of blood clots and endometrial cancer. Raloxifene's breast cancer prevention effects have not been studied in younger women.

Public perception of tamoxifen may have been colored by its side effect profile, even though it is used to treat breast cancer and the NSABP in 1998 showed it could lower the chances of developing the disease.

"As a breast cancer [treatment] drug, it was gangbusters," Dr. Vogel noted. But "for whatever reason, it just never got off the ground for risk reduction."

In Dr. Wickerham's words, "No matter how well it works, if nobody is taking it, it's not going to prevent breast cancer."

Raloxifene, which more than 500,000 American women take for osteoporosis, could represent a safe, effective alternative.

If women choose to use it, "hopefully we'll begin to see a reduction in the number of breast cancers nationally," Dr. Wickerham said.

Before that happens, federal officials must approve raloxifene's use for breast cancer prevention, which Indianapolis-based manufacturer Eli Lilly will request by the end of the year, a spokeswoman said.

Meanwhile, the NSABP is planning a trial to compare raloxifene to drugs called aromatase inhibitors, which have shown promise for reducing breast cancer risk. That study, which has yet to be approved, could have nearly 13,000 participants and might start this year, Dr. Wickerham said.

For more information about breast cancer, NSABP trials, or to calculate your breast cancer risk, go to www.breastcancerprevention.com.

Anita Srikameswaran can be reached at anitas@post-gazette.com or 412-263-3858.


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