A prospective clinical study assessing the presence of exfoliated cancer cells and rectal washout including tumors in patients who receive neoadjuvant chemoradiotherapy for rectal cancer.

Purpose: Rectal washout is performed in rectal cancer surgery to eliminate exfoliated cancer cells. Before rectal washout, a cross-clamp should generally be placed distal to the tumor. In some patients with lower rectal cancer, however, the tumor cannot be adequately isolated. We, therefore, hypothesized that neoadjuvant chemoradiotherapy (nCRT) can decrease the number of exfoliated cancer cells even after the rectal washout including tumors.

Methods: We prospectively studied 86 patients with rectal cancer who underwent proctectomy after nCRT. A cross-clamp was applied proximal to the tumor, and the rectum was washed with 2000 mL of physiological saline solution. The initial 100 mL used to wash the rectum was collected as a pre-washout sample. After the rectum was washed with the remaining 1900 mL, the solution remaining in the rectum was collected as a post-washout sample. Cells classified as class IV or higher according to the papanicolaou classification were considered to indicate a positive diagnosis.

Results: The cytological diagnosis was positive in pre-washout samples in 21 patients (24%) and post-washout samples in two patients (2%).

Conclusion: In patients with rectal cancer, nCRT may decrease the number of exfoliated cancer cells in the rectum, and rectal washout including the tumor may be oncologically acceptable.