Early assessment of a new anticancer drug analogue--are the historical comparisons obsolete? The French experience with pirarubicin.

Data of all phase II studies of pirarubicin (THP-doxorubicin) have been analysed for toxicity or activity in breast cancer and compared with published reports on doxorubicin, epirubicin or mitoxantrone used as single drugs. A graph of the 95% confidence intervals for each event was used. The results suggest that pirarubicin is as effective as other intercalating drugs in breast cancer and grossly better tolerated than doxorubicin, especially alopecia and cumulative cardiotoxicity. The equimyelotoxic doses of each drug were also estimated. The methodology and the validity of such historical comparisons is discussed: they cannot replace prospective randomised phase III studies, and do not allow definitive conclusions. However, most comparative trials of anticancer drug analogues cannot answer the right questions because their objectives are not adequate (especially for equiefficacy). But early evaluation by historical comparisons can help the conception of phase III studies.