Metastatic breast cancer is a leading cause of cancer-related mortality and there has been no major change in the mortality rate over the past few decades. Therapeutic options are available with active drugs such as paclitaxel. However, the promising response rate is also accompanied by a high incidence of toxicities, especially neurotoxicity. An investigator considers testing a new agent that may provide significant prevention, reduction, or mitigation of drug-related toxicity.

This new agent is to be tested against a placebo in a double-blind randomized trial among patients with mestastatic breast cancer who receive weekly paclitaxel. The rate of neurotoxicity over the period of the trial is estimated to be about 40% in the placebo group, and the hypothesis is that this new agent lowers the toxicity rate by one-half, to 20%. Find the total sample size needed using a two-sided level of significance of 0.05 and the assumption that the hypothesis would be detectable with a power of 80%.