An experimental chemotherapy drug called Abraxane was more effective in treating advanced cases of breast cancer and carried fewer side effects than its widely used cousin, Taxol, according to a study released Monday. In another chemotherapy-related study released Friday, the drug docetaxel--widely used for late-stage breast cancer since the mid 1990s--was found to be dramatically better at battling a common early-stage form of the disease than fluorouracil, long a standard treatment. Research by the Breast Cancer International Research Group determined that five years after initial treatment, the docetaxel patients had a 28% lower risk of recurrence than the fluorouracil patients. John Mackey, a breast cancer specialist at the University of Alberta in Canada and a co-leader of the docetaxel study, said the two studies, presented at a breast cancer conference in San Antonio, could soon prompt changes for recommendations in breast-cancer chemotherapy. "People change their (drug recommendations) based on a 2% to 3% improvement," he noted.
A study involving 454 women with breast cancer that had spread elsewhere in the body found that 33% of tumors responded to Abraxane, compared with 19% for Taxol. Abraxane also slowed tumor growth significantly in those patients. Both Taxol and Abraxane are derived from paclitaxel, which works by interfering with a cancer cell's ability to divide. A big difference is how they make their way through the body, and thus how large the dosage can be. Taxol is combined with an oil-based solvent known as Cremophor, whose often harsh side effects limit how much paclitaxel can be delivered to a patient per treatment session. Abraxane, on the other hand, hitches a ride on the naturally occurring human protein albumin, allowing researchers to administer about 60% more paclitaxel per treatment. This approach "allows us, for the first time, to fully maximize the tried-and-true power of paclitaxel," said William Gradishar, a Northwestern University medical professor and a co-director of the study.
The docetaxel study involved nearly 1,500 pre- and post-menopausal women in 20 countries with early-stage breast cancer that had spread into the lymph nodes in the armpit. After five years, 75% of the docetaxel patients had not developed new breast cancer, compared with 68% the fluorouracil patients. Using statistical analysis, the researchers calculated that the chances of relapse using docetaxel are 28% lower than with the other drug.