Rationale: Cytological analysis of pleural effusions (PEs) has a sensitivity of approximately 60%. We hypothesized that the CELLSEARCH technology (Janssen Research and Development, Huntingdon Valley, PA) currently used to detect circulating tumor cells could be adapted for the identification of tumor cells in PEs.
Methods: This was a single-center, prospective, observational study. Pleural fluid from subjects with undiagnosed PEs were analyzed by CELLSEARCH technology, which uses an epithelial cell adhesion molecule antibody-based capture system/cytokeratin antibodies to identify tumor cells. Subjects were prospectively monitored by periodic chart review to determine the etiology of the PE.
Measurements and main results: One hundred thirty-two subjects were analyzed. A malignant etiology was established in 81 subjects. The median number of "positive" pleural epithelial cells (PECs) detected per milliliter of pleural fluid was 6 in the benign group. The number of PECs was 52 in the malignant nonepithelial group (NS) and 526 in the malignant epithelial group (P < 0.001). Unlike blood, there was a baseline number of "positive" cells in benign pleural fluids; however, any cutoff greater than 852 positive cells/ml had 100% specificity. The area under the receiver operating characteristic curve was 0.86. Nine percent of our cancer cases had high numbers of PECs (>280/ml) but a negative or nondefinitive cancer diagnosis by cytology.
Conclusions: The pleural CELLSEARCH assay may serve as a valuable addition to traditional cytology and provide useful information regarding the diagnosis of malignant effusions. Major advantages include that it is well standardized, relatively inexpensive, has a rapid turnaround, and is easily available. Our data support the conduct of additional studies of this approach to assist in the diagnosis of malignant PEs.