Positive peritoneal washing cytology is a potential risk factor for the recurrence of curatively resected colorectal cancer.

ABSTRACT

PURPOSES: Whether free peritoneal cancer cells should be considered peritoneal dissemination in colorectal cancer patients remains controversial. The aim of this study was to investigate the clinical significance of positive peritoneal washing cytology (PWC) in patients with colorectal cancer. METHODS: We retrospectively analyzed the records of 771 sequential patients diagnosed with stage 0-III colorectal cancer who underwent R0 resection and had no distant metastases or peritoneal dissemination. RESULTS: PWC was performed on all 771 patients. Sixty-eight patients experienced metastasis recurrence, 10 of whom experienced peritoneal recurrence. Of the 10 patients with peritoneal recurrence, 6 had positive PWC. Out of the 771 patients, 21 had positive PWC. Of these 21 patients, 6 had peritoneal recurrence, while 4 had distant metastasis and no peritoneal recurrence during the observation period. The 5-year disease-free survival was 89.0 % in the patients with negative PWC vs. 46.8 % in the patients with positive PWC (p < 0.0001, log-rank test). A Cox proportional hazards model revealed that positive PWC was the strongest independent risk factor for cancer-specific recurrence. CONCLUSIONS: Our study highlights PWC as a useful prognostic tool in patients undergoing curative surgery for colorectal cancer, since positive PWC was shown to be a potential risk factor for recurrence.