Assessment of different criteria for the pathological complete response (pCR) to primary chemotherapy in breast cancer: standardization is needed

Purpose Evaluation of the safety and efficacy of a combination of docetaxel and doxorubicin in breast cancer patients. Evaluation and comparison of the pathological complete response (pCR) to this regimen according to various definitions in different clinical trials. Utilize the data to propose standardization of definitions. Patients and Methods Between 1998 and 2001, 141 patients with stage II (tumor size >3.0 cm) or III breast cancer were treated with doxorubicin 50 mg/m² followed by docetaxel 60 mg/m² (AT) on day 1. A total of 4 courses of AT were administered as primary chemotherapy with intervals of 3 weeks. Additionally, 2 cycles of the same regimen were administered after surgery when clinical CR or PR was achieved; otherwise, 4 cycles of CMF were added postoperatively. Results 141 patients were enrolled in this trial. A clinical response rate was 86%. Seven patients (5%) achieved pCR according to the Japanese Breast Cancer Society classification, 14 patients (10%) fulfilled the University of Texas M.D. Anderson Cancer Center trial’s pCR criteria, and 19 patients (14%) met the NSABP trial pCR definition. NCI CTC version 2 grade 3/4 toxicities included leucopenia (26%), neutropenia (85%) and febrile neutropenia (12%). Conclusion Primary chemotherapy with AT induced modest tumor responses with tolerable toxicity. Differences in the definition of pCR among clinical trials caused substantial confusion in interpreting the trial results. Therefore, standardization of the pCR definition after primary chemotherapy is needed.