SAN ANTONIO – New research adds fresh hope that a drug that strengthens bones might also fight breast cancer. Women who were given the drug, Zometa, as part of their initial treatment had greater tumor shrinkage and were less likely to need radical surgery, according to a preliminary study reported Thursday at a cancer conference in Texas.
In June, doctors were stunned when a big study found that Zometa — given to prevent bone loss caused by certain cancer treatments — also greatly cut the risk that cancer would recur in women who developed the disease before menopause.
Cancer specialists are eagerly awaiting the final results of a second, ongoing study testing Zometa in 3,360 women who had breast cancer after menopause — a much more common situation.
Its leaders gave a mini-report Thursday on 205 participants who had chemotherapy to try to shrink their tumors before surgery.
Those given infusions of Zometa along with chemo had a third more tumor shrinkage and as a result, were less likely to need their whole breast removed versus just the lump, said study leader Dr. Robert Coleman of the University of Sheffield in England.
Eleven percent of Zometa takers had a complete response to treatment — no evidence of cancer in their breasts or lymph nodes — versus 6 percent of women given chemo alone.
Partial studies like this are not enough to change practice, but these results are surprising and deserve further testing, said Dr. Eric Winer of the Dana-Farber Cancer Center in Boston. Such significant benefits from the bone drug before surgery "is not something I would have expected," he said.
Winer had no role in the work or financial ties to any breast cancer drugmakers. He also is a spokesman for the American Society of Clinical Oncology, the largest group of doctors who treat cancer.
The study was sponsored by Zometa's maker, Swiss-based Novartis AG, and the study leader consults for the company. With doctor fees, a Zometa infusion can run more than $1,200. In the study it was given every three weeks for four to six months.
Known side effects of Zometa and other bone-building bisphosphonate drugs like Fosamax include bone, joint or muscle pain and in rare cases, jawbone decay. They are mainly used to treat osteoporosis.
Also at the conference, several reports strengthened evidence that newer hormone-blockers called aromatase inhibitors, or AIs, do a better job of preventing cancer recurrences and may give a slight survival advantage over the long-used drug tamoxifen.
These drugs work against estrogen, which helps most breast tumors grow, and are given for about five years after surgery for early stage breast cancer to prevent its return.
Tamoxifen has been used for decades and is sold in generic form for about $70 a month. The newer drugs cost around $300 and come in three brands: AstraZeneca PLC's Arimidex (anastrozole), Pfizer Inc.'s Aromasin (exemestane) and Novartis' Femara (letrozole). They only work in women after menopause.
Doctors already know that women who take these newer drugs either as initial treatment or after a few years of tamoxifen have better chances of staying cancer-free. But which of these approaches is best is not known.
Results of a study led by Novartis consultant Dr. Henning Mouridsen of Copenhagen University Hospital in Denmark mostly were a draw. There were trends toward improved survival for women starting on Femara, but the differences were so small they could have occurred by chance alone.
Specialists took issue with a separate analysis of that study, which hinted at a bigger benefit from starting on Femara. And pooled results of prior studies involving 20,000 women suggest that any such advantage is very small.
"At this point in time, there is a slight increase in survival in patients treated with AIs but it is not statistically significant," said that study's leader, Dr. James Ingle of the Mayo Clinic in Rochester, Minn.
"The only really fair interpretation is that all of these are the same," and that women should include one at some point in their treatment as guidelines now recommend, Winer said.
About 90,000 women in the United States and many more worldwide each year face this decision, and key issues are cost and side effects.
Both drugs can cause hot flashes. Tamoxifen raises the risk of endometrial cancer and blood clots. The aromatase inhibitors can cause more bone loss, vaginal dryness, problems having sex, joint pain and muscle aches.
"Many of us think that overall, they're drugs that are a little harder to take," Winer said of the newer drugs.
"When you put it all together it's almost a balancing act," depending on each woman's health history and risks, said Dr. C. Kent Osborne, a breast cancer specialist at Baylor College of Medicine in Houston.
The San Antonio Breast Cancer symposium is sponsored by the American Association for Cancer Research, Baylor and the University of Texas Health Science Center at San Antonio.