Abstract 4817: Circulating tumor cells enriched by the negative selection system PowerMag is a useful predictor for treatment response of metastatic colorectal cancer patients

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Enumeration of circulating tumor cells (CTCs) provides prognostic and predictive value to guide treatment options. This study aims to (1) evaluate the merits of the PowerMag system, an immunomagnetic separation technique that we recently developed for negative selection of CTCs, in the prediction of treatment response; (2) perform analysis to investigate whether there is a correlation between the imaging response and the changes of CTCs counts before and during chemotherapy for the patients with metastatic colorectal cancer (mCRC). A total of 47 mCRC patients were enrolled in this prospective single-center study. CTCs were isolated from the peripheral blood of these patients by PowerMag at baseline and 2 weeks after starting first dose of chemotherapy. CTCs enumeration was then performed by immunofluorescence staining using the anti-epithelial cell adhesion molecule (EpCAM) antibody. Tumor response at 12 weeks after chemotherapy of the whole cohort was monitored by computed tomography (CT) scans following RECIST criteria 1.0. Our data revealed that PowerMag is a cost-effective negative selection-based CTCs isolation platform with a CTCs detection rate of 89.4% (42/47). The CTCs counts could successfully differ mCRC patients from healthy donors (P = 0.0015). The higher baseline CTCs number was associated with initially metastatic status rather than recurrent settings (P = 0.042). In all assessable patients, a high correlation rate of 86.7% was found between changes of CTCs (decline or elevation) and CT responses (progressive disease, and partial response/stable disease) with a P value of 0.005 (Fisher exact test). These data indicate that the change of CTCs counts before and during treatment is in accord with the image response evaluation at 12 weeks after initiation of treatment. In conclusion, PowerMag is a cost-effective method for negative selection of CTCs from cancer patients. Moreover, comparison of CTCs counts before and during treatment is a useful predictor for disease progression of mCRC patients that warrants further investigation in large-scale validation trial. Citation Format: Jason Chia-Hsun Hsieh, Hung-Chih Lin, Hung-Chih Hsu, John Wen-Cheng Chang, Ching-Ping Tseng. Circulating tumor cells enriched by the negative selection system PowerMag is a useful predictor for treatment response of metastatic colorectal cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4817. doi:10.1158/1538-7445.AM2014-4817