“…However, patients with the same tumor pathology may not respond to the same drug treatment. Tumor heterogeneity is well known in breast cancer [1], Drugs can then be tested in several assays to obtain chemosensitivity profiles [2], The ATP cell viabili ty assay (ATP-CVA) is a relatively new system to assess chemosensitivity by measuring total cell kill [3][4][5][6][7], This test has been adopted for chemosensitivity testing of human gynecologic malignancies, with promising prelim inary results with regard to clinical correlation between in vitro sensitivity and in vivo results. Further, the results of ATP-CVA compare very well with those of other chemo sensitivity assays, especially the clonogenic assay and thy midine uptake methods [3-5, 7, 8], In contrast, the ATP-CVA does not rely only on assessment of S-phase cells (thymidine uptake) or the ability of tumor cells to prolifer ate (clonogenic assay) but on total cell kill.…”