Chemotherapy response assay test and prognosis for breast cancer patients who have undergone anthracycline- and taxane-based chemotherapy

Purpose: A chemotherapy response assay test is performed to evaluate the degree of tumor growth inhibition by a chemothera-peutic agent. Several studies have been done on its usefulness; however, to the best of our knowledge, only a few studies concerning the relationship between chemotherapy response assay test results and breast cancer patients' prognoses have been conducted. Thus, we performed this study to analyze this relationship. Methods: Among breast cancer patients who underwent curative surgery and neoadjuvant or adjuvant chemotherapy between August 2004 and December 2009, 102 were enrolled in this study. Chemotherapeutic regimens for patients were doxorubicin plus taxane or doxorubicin plus cyclophosphamide followed by tax-ane. We divided these patients into two groups (sensitive group [n=19] and resistant group [n=83]) and analyzed the relationship between chemosensitivity results and patient prognosis. Results: The sensitive group was associated with poor disease-free survival (DFS) (p=0.003) and overall survival (OS) (p< 0.001). No sig-nifcant differences were observed in tumor histology (p=0.548), tumor size (p=0.479), number of metastatic lymph nodes (p=0.326), histologic grade (p=0.077), or nuclear grade (p=0.216) between the two groups. However, in respect to molecular subtype, the HER2-positive type and triple negative breast cancer were more frequently observed in the sensitive group (p=0.001). In a univariate and multivariate analysis for DFS, doxorubicin sensitivity was signifcantly associated with a poor prognosis (p< 0.05). Conclusion: Better chemosensitivity results are associated with a poor prognosis in breast cancer patients who have undergone anthracycline- and taxane-based chemotherapy, however, examination of additional cases and the use of a longer study period are needed.