An alternative model for the evaluation of antitumor activity.

To date, in cancer clinical trials, treatment programs have been evaluated using objective tumor response as the primary means to demonstrate antitumor activity. This measure, which is based upon a dichotomous outcome whether or not a 50% decrease in tumor area has occurred, is complemented by the alternative measure of the distribution of the ratio of the tumor area taken at a fixed time point compared to the tumor area at the start of protocol treatment. It is inferred that the distribution of the tumor area ratio obeys a log-normal distribution for advanced gastric cancer and that this result may hold for many advanced measurable cancer studies. The identification of this distribution allows for the evaluation of treatment programs using parametric tests. In situations where log-normality does not apply, a Normal Scores test is recommended. This concept may be applied to completed studies to gain additional perspective regarding antitumor activity. A marked reduction in sample size requirements can be achieved when the tumor area ratio is used as a study design criteria. This approach is especially recommended in the phase II setting.