Bone Drug Offers Hope on Breast Cancer

May 31, 2008 — -- Some early-stage breast cancer patients may soon have a promising new approach to treatment. A major study, released today, found that a drug commonly known to treat brittle bones also showed promise in dealing with early-stage breast cancer and could change the way many breast cancer patients are treated.

Zometa, a drug originally approved by the FDA to treat bone loss in patients undergoing chemotherapy and to reduce bone fractures in osteoporosis patients, might also reduce the risk of disease recurrence in premenopausal breast cancer patients, an Austrian study suggests.

The study, released today at the American Society of Clinical Oncology meeting in Chicago, looked at 1,803 patients with early-stage breast cancer who were undergoing ovarian suppression, a treatment used to prematurely stop menstruation in order to induce menopause in women with hormone-sensitive tumors. By inducing menopause to lower estrogen levels, these hormone-sensitive tumors usually stop growing.

After five years, researchers found that the hormone therapy, when used with Zometa, reduced the risk of breast cancer recurrence by 35 percent compared to patients who received hormone therapy alone.

Moreover, the drug is easily administered and carries little risk of serious side effects, as it requires only one injection every six months.

Michael Gnant, the lead study investigator and professor of surgical oncology at the Medical University of Vienna, said that not only is the study likely to change practice in Europe and the United States, but also might add momentum to the growing demand of many breast cancer patients to avoid chemotherapy.

"To put it into perspective, the number of patients needed to be treated to have one patient who responds very successfully to the drug is quite similar to chemotherapy, but without all the negative and toxic side effects of chemotherapy," Gnant said.

Julie Gralow, associate professor of medical oncology at the University of Washington and director of Breast Medical Oncology at Seattle Cancer Care Alliance, said that this study is likely to change the way many early-stage breast cancer patients are treated.

"I will end up giving it to many of my patients ... with this study being the trigger," Gralow said.

However, the Austrian study involved patients who are not the typical breast cancer patients seen in this country.

The researchers looked only at breast cancer patients who had surgery to remove their primary tumor but who had not undergone chemotherapy -- a patient prototype that would be difficult to find in the U.S., where nearly every young breast cancer patient is recommended chemotherapy.

Despite the fact that this study does not represent the average breast cancer patient in the U.S., Gralow said she will have a hard time refusing to give this drug to her breast cancer patients.

"If a patient comes in and says she wants it, I would say, 'Why not,' since there are hardly any side effects," Gralow said, adding that the study will be "practice changing."

Formerly, a doctor would only recommend Zometa to an osteoporosis patient or a patient with cancer that has spread to her bones. But based on the results of this study, many breast cancer experts are widening their view of which patients would benefit from Zometa.

Many European studies on Zometa and similar drugs, such as clodronate, have also found that these drugs, which are derived from a class of compounds called bisphosphonates, prevented the spread of breast cancer to bone marrow and other organs, thereby reducing the risk of breast cancer relapse.

Although the exact mechanism by which bisphosphonates might help reduce the risk of cancer recurrence is not fully understood, experts hypothesize that the bones might serve as a reservoir for the disease in some patients. By attacking the disease at its root in the bone, so to speak, bisphosphonates may be a key to treating cancer that is as successful as chemotherapy for some patients.

However, without any U.S. clinical trials testing the use of bisphosphonates in breast cancer patients, the FDA denied its approval as an adjuvant therapy for cancer.

But this study seems to change the mind of many breast cancer doctors who were formerly wary of recommending a bisphosphonate such as Zometa as an adjuvant therapy to some of their patients.

"I think that from the perspective of both bone health and breast cancer outcomes, [this study] is going to increase the use of Zometa," said Clifford Hudis, chief of the Breast Cancer Medicine Service at the Memorial Sloan-Kettering Cancer Center. "We can see from this [study] that [Zometa] might allow us to kill two birds with one stone."

Gralow still cautioned that the study involves a narrow group of patients and should not be generalized to every breast cancer patient. But she said when it comes to how she will treat her early-stage breast cancer patients, she will be discussing the use of Zometa and offering it as an option.

Hudis also stopped short of saying he would recommend this drug to all breast cancer patients to reduce the risk of cancer recurrence.

"I think we need more research before we can say that," Hudis said. "We know that the one-size-fits-all approach with cancer treatment never works."