Impact of trastuzumab on the pathological complete response (pCR) rates in primary systemic therapy for breast cancer

Abstract

11000 Background: Various regimens of primary systemic therapy (PST) have been performed to patients with locally advanced breast cancer to decrease the size of the primary tumor and allow for effective local and distant control. In terms of pathological complete response (pCR) rate, however, satisfactory results were not obtained. Therefore, in this study, we have tried to determine whether the addition of trastuzumab on PST could increase pCR rate. Methods: Two prospective nonrandomized studies were performed that used different regimens as PST, followed by breast conserving surgery. Group-A ; Eighty-fore HER2-negative patients with operable breast cancer were assigned to 4 cycles of epirubicin and cyclophosphamide followed by 12 cycles of weekly paclitaxel. GroupB; Eighteen HER2-positive patients were assigned to 4 cycles of epirubicin and cyclophosphamide followed by 12 cycles of weekly paclitaxel and trastuzumab. Results: A total of 102 assessable patients were enrolled, and all the patients have completed the above 2 regimens of PST. Pathological complete response (pCR) rates were 12% in Group-A and 61.1% in Group-B, respectively. Following the PST, 75% of Group-A and all of Group-B patients were able to be subjected to breast conserving surgery. All the toxicities happened in both groups were well controlled in grade 1 or 2. Conclusion: These results indicate that both the PST regimens were safely performed in women with locally advanced breast cancer and allow breast conserving surgery in a high fraction of patients (90%). In addition, significantly high rates of pCR were obtained in patients with use of trastuzumab (p<0.01). No significant financial relationships to disclose.