Circulating tumor cells as a surrogate for treatment response in patients with metastatic pancreatic adenocarcinoma.

Abstract

318 Background: The collection and enumeration of circulating tumor cells (CTCs) are feasible in metastatic breast, prostate and colorectal cancers. CTCs have diagnostic, prognostic and treatment monitoring implications, but have been challenging to detect in pancreatic cancer (PCa). We have proven feasibility of CTCs in PCa. This study is a pilot to assess use of CTCs as a surrogate for imaging response. Methods: Blood samples (7-10mL) from newly diagnosed metastatic PCa were collected within 1 month of treatment initiation (T0) and at repeat scan after 2mo of treatment (T1). Specimens were processed within 6 hours of collection. A UF developed microfluidic device was used to capture and identify EpCam+ CTCs. Isolated cells were verified as CTCs consistent with FDA-approved definitions (cytokeratin+, DAPI+, CD45-). CTC enumeration and changes were correlated with scan RECIST results at T0 and T1. The study was approved by the UF IRB. Results: A total of 16 patients had matched pair CTCs collected and analyzed (Table 1). For the entire cohort, the median CTC count at T0 was 7/mL of blood (range 2-11.5/mL) and decreased to 4.5/mL (range 2-8.5/mL) at T1 (36% reduction). CTCs were reduced to some degree in all patients with therapy. Disease control at T1 was confirmed in 13/16 (81%) with stable disease (n=11), partial (n=1) or complete (n=1) response. Progressive disease was noted in 3 patients. CTCs were reduced by 35% in radiographic stable or responders vs 24% in those with clear progressive disease. Conclusions: This study demonstrated the feasibility of microfluidic technology to reliably and consistently identify CTCs in advanced PCa. While all patients had reduced CTCs with therapy, a trend towards higher reductions were in those with radiographic stable or improved disease. Continued assessment of CTCs in PCa for treatment monitoring are warranted and are ongoing. [Table: see text]