Researchers continue to test the mettle of breakthrough breast cancer drugs, three decades after tamoxifen changed the medical landscape by drastically reducing the risk of recurrences in women with estrogen receptor-positive tumors.
Encouraging findings on several different drugs were presented Thursday at the CTRC-AACR San Antonio Breast Cancer Symposium in Texas.
First in the line-up, the osteoporosis drug zoledronic acid (Zometa) appears to shrink breast tumors in patients who undergo chemotherapy.
The drug is already approved to treat breast cancer that has spread to the bone and, earlier this year, was reported to lower the risk of breast cancer recurrence in pre-menopausal women with early estrogen- or progesterone-positive tumors.
In an analysis of slightly more than 200 women, those who received Zometa in addition to chemotherapy had better results than those receiving chemotherapy alone. After compensating for variables such as estrogen receptor status and treatment duration, residual invasive tumor size was 42.4 millimeters in the chemotherapy alone group, and 28.2 millimeters in the combination group.
"This data suggests that zoledronic acid is doing something more than protecting bone," said study senior author Dr. Robert Coleman, a professor of medical oncology at the University of Sheffield in England. "It's not practice-changing. It's hypothesis-generating, which will lead to the design of new trials to look at this in detail. But this is the first patient-related evidence."
Coleman spoke, along with researchers involved with other trials, at a Thursday teleconference. Other studies showing promise included:
Postmenopausal women with estrogen receptor- and/or progesterone receptor-positive breast cancer who took the aromatase inhibitor exemestane (Aromasin) had a 15 percent relative reduction in recurrences and a 19 percent reduction in the risk of distant metastasis, compared with those taking tamoxifen alone. "Exemestane is very effective at preventing recurrences," said Dr. Stephen Jones, medical director of U.S. Oncology Research in Houston.