Chemosensitivity profile assay of circulating cancer cells: prognostic and predictive value in epithelial tumors

The prognostic value associated with the detection of circulating tumor cells (CTCs) in metastatic breast cancer by the CellSearch™ technology raise additional issues regarding the biological value of this information. We postulated that a drug‐resistance profile of CTCs may predict response to chemotherapy in cancer patients and therefore could be used for patient selection. One hundred 5 patients with diagnosis of carcinoma were enrolled in a prospective trial. CTCs were isolated from peripheral blood, and positive samples were evaluated for the expression of a panel of genes involved in anticancer drugs resistance. The drug‐resistance profile was correlated with disease‐free survival (DFS; patients in adjuvant setting) and time to progression (TTP; metastatic patients) in a 24‐months follow‐up. Objective response correlation was a secondary end point. Fifty‐one percent of patients were found positive for CTCs while all blood samples from healthy donors were negative. The drug‐resistance profile correlates with DFS and TTP (p < 0.001 in both). Sensitivity of the test: able to predict treatment response in 98% of patients. Specificity of the test: 100%; no sample from healthy subject was positive for the presence of CTCs. Positive and negative predictive values were found to be 96.5 and 100%, respectively. We identified a drug‐resistance profile of CTCs, which is predictive of response to chemotherapy, independent of tumor type and stage of disease. This approach may represent a first step toward the individualization of chemotherapy in cancer patients.