Detection of CTCs in Patients Undergoing Surgery for Stage IV Colorectal Cancer

Overview

Colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States. About 90% of CRC related deaths are due to metastatic spread-mostly to the liver and lungs. With adequate multidisciplinary patient selection, CRC liver and lung metastasectomy significantly improves survival and offers the best chance for a cure. However, patients with limited lung or liver metastases are clinically underserved and poorly scientifically studied. The individual indication for resection and the decision making for adjuvant systemic therapies remains a challenge. More sensitive techniques to detect occult disease are needed for metastatic CRC (mCRC) patients, and perioperative analysis of circulating tumor cells (CTCs) may provide an outstanding opportunity to develop such innovative methods. We hypothesize that CTCs are enriched during CRC liver and/or lung metastasectomy, and that they can be isolated and characterized in an attempt to identify novel therapeutic targets. CTCs are believed to be causing metastasis and may provide a non-invasive alternative to organ biopsies for the detection, characterization and monitoring of solid cancers. CTC numbers have been shown to be a strong predictor of Progression Free Survival and Overall Survival for mCRC patients. The CellSearch system (Veridex LLC, Ratinas, NJ, USA) currently is the only FDA approved test for the evaluation of CTC numbers in metastatic breast, prostate and colorectal cancer. However, the rarity of CTCs in the blood leads to limited capture efficiency and the CellSearch system fixes cells, preventing further molecular characterization of CTCs by functional assays and primary cell culture. In this protocol the CellSearch system will be compared to a new technology, called the Flexible Micro Spring Array (FMSA) device, developed by Dr. Zheng, Department of Bioengineering, Penn State University, University Park. This novel approach enables size-exclusion based filtration for viable CTC enrichment. The FMSA device is inexpensive, works rapidly, and retains viable CTCs for further biological study. Using both the CellSearch system and the FMSA device, we will determine the kinetics of CTC shedding into circulation, develop an effective system for isolation, enumeration, and further enrichment CTCs, and use this system to find characteristics of different CTC populations.

More sensitive techniques to detect occult disease are needed for metastatic CRC (mCRC) patients, and perioperative analysis of circulating tumor cells (CTCs) may provide an outstanding opportunity to develop such innovative methods. Determine kinetics of CTC shedding into the circulation: Perioperative CTC detection has the potential to explain how and when CTCs are shed into the blood. Findings could explain the nature of CTCs with important impact on understanding metastatic spread and relevant clinical applications. Since this protocol includes blood draws at multiple time points at different distances from the metastases, results could further clarify if the rarity or absence of CTCs in the peripheral blood of some mCRC patients can be explained by dilution. Comparison of patients with CRC liver to lung metastases might help explain different patterns of organ spread. Results of this study could establish CTCs as a prognostic biomarker identifying candidates who will benefit from metastasectomy or for those who are candidates for additional or palliative systemic treatments because of a high risk for later recurrence. * Develop effective system for isolation, enumeration, enrichment and further characterization of live CTCs: One of the current issues of CTC analysis is the enrichment of those rare cells from blood. We plan to analyze perioperatively drawn blood using the flexible micro spring array (FMSA) device. The FMSA mitigates the stresses experienced by CTCs during their isolation from blood and enables viable capture. The geometric design and filtration pressures have been optimized to maximize capture efficiency, enrichment against leukocytes, and tumor cell viability. Peripheral blood as well as blood from the direct tumor environment (taken from the OR suctioning system) will be analyzed to compare the sensitivity of the FMSA and CellSearch device. Since the FMSA allows for isolation of live CTCs, they will be processed for further single cell characterization. * Find characteristics of different CTC populations: We hypothesize that CTCs will be enriched for cancer stem cell markers as well as markers for poor prognosis and aggressive tumor growth. Our novel approach to screen and quantify a panel of biomarkers simultaneously with analysis of the CTC markers utilized by the CellSearch system to analyze of CTCs is unique. We view our assays as potential "liquid biopsies" that can screen for markers of prognosis, sensitivity to chemotherapy, response to therapy, as well as for proteins involved in proliferation, apoptosis, and immune response. Furthermore, we plan to perform single cell analysis of gene mutations and gene expression. Next generation genomic sequencing of single CTCs may allow us to determine a genetic signature for colorectal CTCs and to identify novel biomarkers for CTC detection, disease monitoring, and therapeutic efficacy. Furthermore, the extent of heterogeneity among initially isolated CTCs, which can be compared to the primary tumor and CTCs growing in vitro, will be studied. Single CTC analysis has the potential to identify novel gene and signal transduction pathways that are activated in CTCs and to compare this genomic profile to that of the primary tumor and patient metastasis. Single cell genomic analysis in CTCs is highly innovative and will provide important information for disease monitoring as well as shed light on the underlying biology of CTCs.