In vitro analysis of exfoliated tumor cells in intraluminal lavage samples after colorectal endoscopic submucosal dissection

Abstract

Purpose: Colorectal endoscopic submucosal dissection (ESD) produces exfoliated tumor cells that occasionally cause local recurrence. However, the biological characteristics of these tumor cells have not been clarified. The aim of this study was to clarify the genetic background and viability of exfoliated tumor cells in colorectal ESDs, as well as possible method for their elimination.

Methods: Post-ESD intraluminal lavage samples from 19 patients who underwent colorectal ESDs were collected. In four patients with adenocarcinoma, gene mutations in the primary tumors and exfoliated cells in lavage samples were analyzed using a next-generation sequencer (NGS). In 15 patients with adenoma or adenocarcinoma, the viability of exfoliated cells and the cell-killing effect of povidone-iodine on exfoliated cells were evaluated.

Results: The analysis using a NGS demonstrated that tumors targeted for ESD had already acquired mutations in many genes involved in cell proliferation, angiogenesis, and invasions. Furthermore, gene mutations between the exfoliated tumor cells and tumors resected by ESDs showed a 92 to 100% concordance. The median viable cell counts and the median viability of exfoliated cells in intraluminal lavage samples after ESDs were 4.9 × 10⁵ cells/mL and 24%, respectively. The viability of the exfoliated cells did not decrease even 12 h after ESD. However, contact with 2.0% povidone-iodine solution reduced both viable cell counts and viability, significantly.

Conclusion: A large number of tumor cells exfoliated during colorectal ESDs had acquired survival-favorable gene mutations and could survive for some time. Therefore, a lavage using a solution of 2.0% povidone-iodine may be effective against such cells.

Trial registration: The prospective study registered 1317, and the retrospective study registered 2729. The prospective study approved on June 20, 2016, and the retrospective study approved on October 6, 2020.

Keywords: Cell survival; Colorectal neoplasm; Endoscopic submucosal dissection; Mutation; Therapeutic irrigation.