Role of Circulating Tumor Cells by Rare Cell Enumeration System in Predicting Response of Non-Small Cell Lung Cancers to Therapy.

e24058 Background: We aim to investigate role of circulating tumor cells (CTC) as supplementary marker to imaging to predict response to therapy in non-small cell lung cancer (NSCLC) patients (pt). We hypothesized “CTC rise post therapy is associated with radiologic progression or progression of NSCLC in near future”. We used a new CTC enumeration system (Rare Cell), which collects epithelial and mesenchymal CTC from blood, instead of Cell search. Methods: CTC were collected from whole blood of Stage III and IV NSCLC pt before and after therapy. Data was correlated with radiologic response. Chi-square and t-test analysis were performed as appropriate. Results: 9 pt with stage IV and 1 with stage IIIB NSCLC were analyzed. In 4 pt with response & 3 with progression Δ in CTC correlated with images. 3 pt had discordant results (see table). Pt with higher baseline CTC had greater radiologic response. Baseline CTC > 4 also resulted in higher CTC response (-2.50±1.00 vs 2.33±1.21, p<0.001). Conclusions: Radiologic findings and ΔCTC correlated well in majority of NSCLC pt. Higher response rate with higher baseline CTC might suggest aggressiveness of the disease, making it more sensitive to therapy. In pt with discrepancy between imaging and CTC, increase in CTC was predictive of disease progression in near future. Trending CTC helps augment response assessed by routine imaging. Oncologists can consider imaging in short intervals (4-6 weeks) for pt with CTC increase despite radiologic response. Table 1. Subject Pathology Pre therapy CTC Post therapy CTC CTC Responders Radiological Responders Comment 1 Adenocarcinoma 4 3 Yes Yes 2 Squamous 6 3 Yes Yes 3 Squamous 3 5 No Mixed Post treatment imaging showed 36% shrinkage of primary tumor but increase in pleural nodules. Scans in 4 weeks showed progression. Pt died within 8 weeks of CTC rise 4 Squamous 1 2 No No 5 Adenosquamous 2 5 No No 6 Adenocarcinoma 3 7 No Mixed Post therapy scans showed response but CTC increased. Scans in 3 months showed progression of disease. However, pleurodesis was done prior to 2nd CTC 7 Adenocarcinoma 4 1 Yes Yes 8 Adenocarcinoma 2 3 No No 9 Squamous 4 1 Yes Yes 10 Adenosquamous 2 5 No Yes Pt developed liver metastases within 6 months of rise in CTC