Sample size determination in clinical trials (and other similar studies) depends on a number of factors including the distribution of patient survival (remission) times, available estimates of the requisite parameters of the distribution under the null and alternative hypotheses, sizes of the Type I and Type II errors, and the length of the clinical trial, which in turn determines whether there are many, few, or no censored observations with regard to patient survival (remission). A further consideration is the patient recruitment period, which is assumed to begin simultaneously with the clinical trial but whose length is less than the length of the clinical trial. The purpose of this article is to explore the optimum lengths of the clinical trial and the recruitment period on the basis of minimizing the expected cost of the trial. A specified cost function, patient entry distribution, and exponential survival distribution are all assumed, primarily for illustrative purposes.

In this study sensitivity of human transitional cancer cells to the anticancer agent paclitaxel, an antimicrotubular drug, and to gallium nitrate, a group IIIa metal, was compared to that of the standard MVAC (methotrexate, vinblastine, doxorubicin and cisplatin) drugs. The reduction of cell proliferation was evaluated after 48 h of incubation of six different cell lines with each agent using the mean transit time (MTT) assay. We investigated both monolayers and spheroids. Paclitaxel showed significantly higher growth inhibitory effects on monolayers than vinblastine, both agents targeting the antimicrotubular apparatus. This could not be reproduced on spheroids, where a survival fraction of 50% was observed even at high concentrations (10 microM). High concentrations of gallium nitrate were needed to achieve sufficient toxicity. These concentrations are beyond the concentration achievable by systemic application. Our findings suggest that paclitaxel may be a clinically useful agent for systemic and intravesical use in bladder cancer.

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