Heterogeneous chemosensitivity of breast cancer determined by adeonsine triphosphate based chemotherapy response assay

Purpose: Breast cancer is heterogeneous disease and the response to chemotherapeutic agents is also heterogeneous from patient to patient. Chemotherapy response assay is in vitro test that is performed to evaluate the degree of tumor growth inhibition by chemotherapy drugs. In this study, we performed the chemotherapy response assay using adenosine triphosphate (ATP-CRA) in breast cancer patients and assessed the clinical availability. Methods: Sixty five breast cancer patients were enrolled in this study. Cancer cells were evenly divided and treated with commonly used chemotherapeutic drugs in breast cancer (doxorubicin, epirubicin, 5-fluorouracil, paclitaxel, docetaxel, vinorelbine, and gemcitabine). To verify in vitro ATP-CRA indirectly, we analyzed the correlation between cell death rate (CDR) of doxorubicin and epirubicin, and between doxorubicin and paclitaxel. We also analyzed the mean CDR of doxorubicin, epirubicin and paclitaxel by HER2 status. Results: We could successfully perform the ATP-CRA in 60 patients (95.2%). In all cases, we can get the results within 7 days. The range of CDR was very wide, from 0 to more than 50%, except gemcitabine. Epirubicin showed the highest mean CDR (39.9%) and doxorubicin, paclitaxel in order. According to the chemosensitivity index, paclitaxel is the most frequently first-ranked and doxorubicin, epirubicin in order. Correlation coefficient between the cell death rate of doxorubicin and epirubicin is 0.4210 and 0.1299 between paclitaxel and doxorubicin. In HER2 positive group, mean CDR of paclitaxel, epirubicin and doxorubicin washigher than in HER2 negative group, even though epirubicin and doxorubicin were not statistically significant (p=0.018, p= 0.114, p=0.311, respectively). Conclusion: ATP-CRA showed heterogeneous results in individual patients. ATP-CRA was successful and can be performed within short time period. According to our in vitro study, it showed similar results with in vivo study but for the clinical use, the prospective andomized controlled trial should be preceded.