Success rates and clinicopathologic associations with experimental outcomes of a novel circulating tumor cell (CTC) technology in advanced colon cancer (CC) and pancreatic cancer (PC).

Abstract

805 Background: Studying CTC cultures (cx) ex-vivo can provide valuable insights into cancer metastases (mets). However, current immunoaffinity- and size-based-methods used to isolate and expand these cells have low success rates for culturing CTCs (6-20%). Here, we report our experience using a novel technology developed at Georgetown for culturing CTCs from patients (pts) with metastatic (m) CC, mPC, and locally advanced PC (LAPC). Methods: 44 peripheral blood samples were prospectively collected from 35 pts with adenocarcinoma across 3 cohorts (18 samples from 15 mCC pts, 21 samples from 15 mPC pts, and 5 samples from 5 LAPC pts). Pts were previously treated, treatment-naïve, or actively undergoing treatment. FiColl-Paque-based separation of red blood cells was performed, plasma and buffy coat cells were resuspended in cx medium, and successfully grown CTC cxs were processed and injected subcutaneously (subQ) in the flanks of mice. A single predetermined sample from each pt was used in assessing the clinicopathologic associations with experiment outcomes and survival analyses. Results: CTC cxs were successfully grown from 81.8% (36/44) of all samples. Cxs grew from 72.2% (13/18) of mCC, 85.7% (18/21) of mPC, and 100% (5/5) of LAPC samples. At the time of analysis, 25 injected mice were evaluable for subQ tumor growth. 4 mice failed to grow tumor, 10 were still under monitoring, and 11 grew tumor, 9 of which also developed mets. These were mostly macro-mets and partially mirrored the met pattern seen in the matched pt. Across all cohorts, samples were predominantly collected from pts during systemic treatment (79.5%), during 2nd- (36.4%) and 1st-line treatment (20.5%), at a median of 15 (0-111) and 5 (1-20) months after diagnosis in mPC/mCC and LAPC pts, respectively, after scans with new/progressing disease (72.7%), and with a median of 3 (1-9) sites of disease on scans done within 2 months of collection . In all pts, no clinicopathologic or genomic factor predicted for cx growth. In the mCC subgroup, female sex (p=0.044), longer time from diagnosis to CTC collection (p=0.033), and presence of lung mets (p=0.022) were associated with cx growth. With cohorts combined, the median pt progression-free survival was 174 days (95% CI 97-220) and median overall survival was not reached. There was no statistically significant relationship between cx growth and pt survival. Conclusions: This novel platform demonstrated historically high rates of successful CTC cx and xenograft tumor growth using samples from advanced CC and PC pts. Studies to elucidate reasons for mice failing to grow tumor and others with matched tumor-CTC molecular analyses are ongoing to validate this promising technology to ultimately use to identify biomarkers for metastases, uncover novel therapeutic targets, and inform clinical decisions.