Can neoadjuvant chemoradiotherapy affect exfoliated cancer cells in colorectal cancer?

Background: To prevent local recurrence caused by exfoliated cancer cells caught in the suture line, intraoperative rectal washout during surgery can be performed to eliminate exfoliated cancer cells. However, the impact of neoadjuvant chemoradiotherapy on exfoliated cancer cells is not well known. This study aimed to identify positive rate of malignant cells in rectal washout fluids of neoadjuvant chemoradiotherapy patients and to determine if neoadjuvant chemoradiotherapy could affect exfoliated cancer cells. Methods: A total of 105 patients who underwent rectal washout intraoperatively for distal sigmoid colon and rectal cancer from April 2020 to September 2021 were analyzed. The primary outcome was positive rate of malignant cells in rectal washout fluids of patients who had received neoadjuvant chemoradiotherapy. Results: The positive rate of malignant cells in washout fluids of patients who had received neoadjuvant chemoradiotherapy was 0.0% and those who had not was 32.1%. The overall positive rate was 23.8%. In the positive group, tumor sizes were bigger (4.64 ± 1.68 cm vs. 3.64 ± 2.00 cm, p = 0.026) and more patients had a fungating tumor shown in preoperative colonoscopy (96.0% vs. 71.3%, p = 0.012). Although these factors did not show statistical significance in multivariable logistic regression analysis, fungating tumor showed a trend towards significance (OR: 7.28, 95% CI: 0.90-58.77, p = 0.063). Conclusions: Our study suggests that neoadjuvant chemoradiotherapy could reduce exfoliated cancer cells, and rectal washout for the purpose of eliminating exfoliated cancer cells might be unnecessary in patients who have received neoadjuvant chemoradiotherapy.