Correlation of Early Systemic Recurrence withIn VitroAdenosine Triphosphate-Based Chemotherapy Response Assay in Stage II and III Breast Cancer Patients Treated with Doxorubicin-Based Chemotherapy

(EBCTCG)5015 Purpose: An in vitro adenosine triphosphate-based chemotherapy response assay (ATP-CRA) was designed to require only a limited number of cells and shorten test turnaround time with a high success rate. This study investigated the correlation between in vitro doxorubicin sensitivity of tumor cells and early systemic recurrence, defined as recurrence within 2 years after surgery. Methods: From January 2004 to March 2007, the ATP-CRA for doxorubicin was tested in 128 patients among breast cancer patients treated at Gangnam Severance Hospital, Seoul, Korea. The American Joint Committee on Cancer stages for all patients were II and III. All patients received doxorubicin-based chemotherapy. Selected patients were divided into a chemosensitive group and a non-chemosensitive group, according to a 40% cell death rate as a cut-off value. We analyzed the relationship between chemosensitivity and early systemic recurrence in patients with breast cancer. Results: The mean age of the patients investigated was 44.6-years-old, the mean follow-up period was 39.9 months, and recurrence free survival was 38.6 months. Thirteen recurrences were observed during follow-up. Among 13 patients with a recurrence, eight had a recurrence within 2 years (early recurrence). All of the early recurring patients belonged to the non-sensitive group. Doxorubicin sensitivity results measured by ATP-CRA were related with early recurrence free survival in patients with breast cancer (p=0.030). The mean cell death rate derived from the ATP-CRA for the early recurrence group tended to be lower than that of the non-early recurrence group, but the difference was not statistically significant (p=0.05). Conclusion: Doxorubicin sensitivity measured by ATP-CRA was well correlated with in vivo drug responsibility to predict early recurrence against doxorubicinbased adjuvant chemotherapy in patients with breast cancer.