NCI's CHABNER QUESTIONS TAXOL ADMINISTRATION LABELING CHANGE

NCI's CHABNER QUESTIONS TAXOL ADMINISTRATION LABELING CHANGE recommended by FDA's Oncology Drugs Advisory Committee at its Sept. 23 meeting. The committee agreed that paclitaxel should be infused over three hours rather than the currently recommended 24 hours ("The Pink Sheet" Sept. 27, T&G-8). National Cancer Institute Division of Cancer Treatment (DCT) Director Bruce Chabner commented on the proposed change at the Oct. 18-19 meeting of DCT's Board of Scientific Counselors.

"I have reservations about the decision to relabel Taxol," Chabner asserted. "I realize the logistic advantages of three-hour infusions; however, preclinical studies clearly indicate that the drug's activity increases with longer durations of drug exposure. Given its rapid half-life of two hours, the three-hour infusion could well be inadequate to give optimal exposure."

He added that according to results of a recently completed trial, a 48% response rate was observed in 33 patients with relapsed breast cancer who were given a 96-hour infusion. "I am concerned that the general adoption of the three-hour schedule, which is bound to happen because of its convenience, could lead to a significant lowering of the response rate in ovarian and breast cancer patients," Chabner maintained.

The FDA Oncology Drugs Advisory Committee recommended that Taxol be infused over three hours instead of 24 hours because they decided that the shorter infusion time would be less toxic and more convenient. The committee could not recommend a specific dose for Taxol. The FDA advisors based their decision on a study by the National Cancer Institute of Canada in relapsed ovarian cancer patients comparing three- and 24-hour schedules, at a dose of either 135 mg/m or 175 mg/m.

The drug is currently labeled with a recommended dosage schedule of 135 mg/m over 24 hours. Bristol-Myers Squibb has submitted a supplemental NDA proposing that the regimen be changed to 175 mg/m over three hours.

Chabner noted that patients who received 175 mg/m had a higher response rate in the Canadian study, while no difference was detected between the three-hour and 24-hour schedule when all doses were grouped together. However, he asserted that when individual parts of the trial were analyzed, the 175 mg/m at 24-hour schedule group had a 26% response rate, compared to a 19% response rate for the three-hour schedule at the same dose. He added that there were 80 patients in each arm of the study, "too few to allow detection of a significant difference" between the two schedules.

NCI's Cancer Therapy Evaluation Program is planning to fund a contract to compare three- hour and 96-hour schedules of Taxol at maximum tolerated doses. The study, which is expected to begin soon, according to CTEP Director Michael Friedman, will probably be conducted at Memorial Sloan-Kettering Cancer Center and M.D. Anderson Cancer Center in a small number of relapsed breast cancer patients.