Comparisons of Cooperative Group evaluation criteria for multiple-drug therapy for breast cancer

The variability of response rates and durations for multiple-drug therapy for advanced breast cancer may be due in part to the evaulation criteria of the investigators. To assess the impact on outcome, a single data set comprising the patients registered in Central Oncology Group protocol 7020B was analyzed by the evaluation criteria of the Central Oncology Group, the Eastern Cooperative Oncology Group, the Southwest Oncology Group, and the Southeastern Cancer Study Group, as well as by a personally derived "flexible clinical interpretation of treatment benefit." The response rates and durations were quite similar by the criteria of all groups except those of the Southeastern Cancer Study Group, which gave lower rates and longer duration. These differences were consistent with the evaluation criteria for each group and confirmed the differences noted in their published reports. When "flexible" criteria were used, the differences deviated from those using strict group criteria. This might explain, in part, reports from single institutions of response rates that were higher than those achieved in cooperative group studies.