Abstract 1592: Bladder cancer circulating tumor cell concentration fluctuates in the absence of systemic therapy or surgery
Authors: Glavaris Stephanie A. , Chalfin Heather J. , Fong Megan H. , Christenson Eric , Ahmed A. Karim , Caruso Emily A. , Shin John , Johnson Michael , Dong Liang , Gorin Michael A. , Bivalacqua Trinity J. , Pienta Kenneth J. , Hahn Noah , McConkey David 
Published: August 2018

Background: "Liquid biopsies" such as circulating tumor cells (CTCs) aim to monitor response to therapy or provide a noninvasive measure of disease progression. In bladder cancer, it is not known to what extent CTC counts fluctuate over time during the same treatment phase (in the absence of systemic therapy or surgery). Understanding the baseline variation in CTC counts is a crucial step towards defining what constitutes a meaningful change in CTC detection. Here, we collected peripheral blood (PB) samples from metastatic bladder cancer patients with replicates from the same date and at multiple time points over different days.

Methods: 3 replicate PB samples (A, B, C) were collected on Day 1 from 5 metastatic bladder cancer patients. On Days 2 and 3, PB was collected from 80% (n=4/5) patients. The median CTC count of the 3 replicates from Day 1 was used. Each PB was processed with the AccuCyte® system to isolate and transfer the buffy coat onto 8 slides. Slides were stained with DAPI (nuclear), anti-pan-cytokeratin and anti-EpCAM (epithelial), and anti-CD45/CD66b/CD34/CD14/CD11b (white blood cell) antibodies. Slides were scanned and analyzed using the CyteFinder® system, an assay validated to have high recovery (greater than 80%) and sensitivity for detecting individual CTCs (DAPI positive, epithelial-marker positive, and white blood cell marker negative).

Results: For replicate samples, the range of CTC counts/7.5 mL PB for Patient 1 was 70 (A=43, B=102, C=32), Patient 2 was 5 (A=6, B=2, C=1), Patient 3 was 1 (A=1, B=0, C=0), Patient 4 was 2 (A=2, B=4, C=2), and Patient 5 was 1 (A=1, B=1, C=0). The median of the ranges (70, 5, 1, 2, 1) was 2 CTCs/7.5 mL PB. For PB collected on different days, the range of CTC counts for Patient 1 was 192 (43, 170, 235), Patient 2 was 11 (2, 13, 5), Patient 3 was 3 (0, 3, 3), and Patient 4 was 4 (2, 5, 6). The median of the ranges (192, 11, 3, 4) was 7 CTCs/7.5 mL PB.

Conclusion: While the median fluctuations of 2 and 7 CTCs/7.5 mL PB were low, in certain cases we did detect considerable variation in CTC count from sample to sample and from day to day. Ongoing work is necessary to study the natural fluctuation in CTC counts and the heterogeneity of blood CTC concentration from moment to moment. Given the many challenges of CTC detection, ctDNA may emerge as the preferred liquid biopsy in bladder cancer.

Citation Format: Stephanie A. Glavaris, Heather J. Chalfin, Megan H. Fong, Eric Christenson, A. Karim Ahmed, Emily A. Caruso, John Shin, Michael Johnson, Liang Dong, Michael A. Gorin, Trinity J. Bivalacqua, Kenneth J. Pienta, Noah Hahn, David McConkey. Bladder cancer circulating tumor cell concentration fluctuates in the absence of systemic therapy or surgery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1592.