Taxotere Beats Taxol in Comparison of Breast Cancer Drugs

Newswise — Taxotere and Taxol, two of the most promising drugs to be developed for the treatment of life-threatening metastatic breast cancer in the last decade, were tested head to head in a clinical trial of 449 women, and Taxotere proved to be more effective at shrinking tumors and extending life span, said principal investigator Peter M. Ravdin, M.D., Ph.D., clinical professor of medicine at The University of Texas Health Science Center at San Antonio (UTHSC). He presented the study results Sept. 24 in Copenhagen, Denmark, at the European Conference of Clinical Oncology.

Every woman enrolled in the Phase III trial had metastatic breast cancer or locally advanced breast cancer. Both pre- and post-menopausal women participated; half were given Taxotere and half Taxol. "In all groups, there was a trend for Taxotere to be a better drug," Dr. Ravdin said. Taxotere recipients showed greater tumor shrinkage and tended to live longer " 15.4 months on average vs. 12.7 months for Taxol recipients. "Although that's a modest difference, for those people who lived longer it was important," Dr. Ravdin said. "And when a therapy demonstrates a survival advantage compared to another therapy for advanced metastatic breast cancer, that advantage often is translated into an advantage for patients with early breast cancer, where adjuvant therapies have curative potential." A trial comparing the two drugs is being conducted in patients with early breast cancer.

More side effects were reported in the women who received Taxotere, including low white blood cell counts and infections when white counts were low. "Taxotere was the more effective therapy, but it was also the therapy that carried more risk," Dr. Ravdin said. Among the women treated with Taxotere, 14 percent had fever while their white blood counts were low, compared to 2 percent of those treated with Taxol. Medical oncologists are able to manage the side effects effectively in the clinical setting.

Taxol is a derivative of the Pacific yew tree, while Taxotere is a similar drug made by a semi-synthetic process. The body metabolizes the two drugs differently. They interact in slightly different ways with microtubules, small structures in cells that are important for cell division. "The disruption of the microtubules' action has strong effects on cells that are rapidly trying to divide, such as cancer cells," Dr. Ravdin said.

Taxol was discovered by screening many natural compounds, including bark of the Pacific yew. Taxotere subsequently was discovered by researchers who were analyzing compounds closely related to Taxol. Phase I and II clinical trials to determine the safety and efficacy of the drugs in humans were conducted at multiple institutions, including the Health Science Center and its San Antonio partner, the Cancer Therapy and Research Center. The drugs have been under study for about 10 years at the two institutions, Dr. Ravdin said.

Sixteen women participated in the trial at the San Antonio site. The study was supported by Aventis Pharmaceutical, maker of Taxotere.