Taking hormone-blocking pills for a few months before breast cancer surgery can shrink tumors and allow many women to have just the lump removed instead of the whole breast, a new study suggests.
This approach is sometimes tried now in Europe, and the study was the first large test of it in the United States. It won't change practice right away; a second study is starting to try to repeat the results and identify which drugs work best.
Ultimately, though, this new approach could affect the care of tens of thousands of women each year with large tumors whose growth is fueled by estrogen. It might give them not just a gentler surgery option, but also may let many of them skip chemotherapy.
Before being treated with the hormone blockers, most of the women in the study were facing likely mastectomies because their tumors were too large for less drastic surgery.
"Half of them wound up having successful breast-conserving therapy," said Dr. John Olson, breast cancer surgery chief at Duke University. "That is a huge deal."
He led the study and gave results in a telephone news conference Wednesday. They will be presented Saturday at a meeting of the American Society of Clinical Oncology and several other groups in Washington. Results also have been sent to a scientific journal and are under review.
Of the more than more than 200,000 breast cancers diagnosed each year in the U.S., about 70 percent have their growth fueled by the hormone estrogen.
The study involved 374 women at more than 100 sites around the country whose tumors were especially sensitive to estrogen. Doctors already know that chemotherapy is less effective in such women, and they wanted to see whether hormone-blocking drugs would work well enough to allow more of these women to be treated without removing their breasts.
Tamoxifen used to be the gold standard hormone blocker, but newer drugs called aromatase inhibitors do the job with fewer side effects.
The women in the study were randomly assigned to get one of three such medicines: Pfizer Inc.'s Aromasin, Novartis' Femara or AstraZeneca PLC's Arimidex. They cost from $340 to $420 a month, although Arimidex is available in generic form and patents on the others expire within a few years.
After four months, 71 percent on Femara, 67 percent on Arimidex and 61 percent on Aromasin had tumors shrink by half or more. Half of the women who were originally told they needed mastectomies were able to have lump-only surgery, as were about 82 percent of those who were thought to be marginal candidates for the less severe operation.
Only 23 women saw their tumors grow 25 percent or more in the four months that surgery was delayed.
That risk is fairly small and compares to what studies testing chemotherapy before surgery have found, said Dr. Harold Burstein, a breast cancer specialist at Dana-Farber Cancer Institute in Boston who heads the oncology society's expert panel on hormone treatments.
For most women, delaying surgery to try tumor-shrinking treatment is a reasonable option, he said.
"Hopefully we can build on this and identify women who don't need chemotherapy" and can have hormone-blockers instead, he said.
The side effects of hormone treatment are milder — mostly hot flashes and joint pain, Olson said.
A National Cancer Institute grant paid for most of the study; Pfizer and Novartis contributed some support.
Although the differences in how well the three drugs performed were so small they could have occurred by chance alone, the larger study will test the two with the best results — Femara and Arimidex, Olson said. It also will compare them to chemotherapy as a pre-surgery treatment.