Analysis of prognosis in colorectal mucinous adenocarcinoma: A retrospective analysis with peritoneal fluid

Purpose: Although many papers have reported poor prognosis of colorectal mucinous adenocarcinoma, the underlying cause for its unfavorable outcome is yet to be elucidated. In the peritoneal fluid studies, we observed that peritoneal recurrences and cytology positive cases were many times mucinous cancers. On the basis of these observations, mucinous and non-mucinous adenocarcinomas were compared and prognostic factors were studied. Methods: Five hundred and forty-six patients who underwent surgery for colorectal adenocarcinomas from January 2004 to December 2008 were included. Results: Among the 546 patients, mucinous adenocarcinomas were 30 (5.5%) and non-mucinous adenocarcinomas were 516 (94.5%). Mean age was 55.0 years, which was younger than 63.2 years in non-mucinous colon cancers. They tend to develop in the right colon. Mucinous adenocarcinomas were more advanced in depth of invasion and distant metastasis, but no significant difference in lymph node (LN) metastasis. Peritoneal CEA, CA19-9, and positive cytology were more apparent. Liver and peritoneal metastasis did not show significant increases. Five year survival rates were 82.9% and 91.7% and cancer free survival rates were 42.7% and 68.5% each, respectively, for mucinous and non-mucinous cancers. According to stage, only stage III and IV patients showed differences in cancer free survival and overall survival (P=0.001, 0.040). Conclusion: Mucinous adenocarcinomas showed worse prognoses and significant differences in recurrences, but had similar prognoses in early cancers. Although no significant differences were in LN metastasis, dissimilarities were in infiltration depth. Infiltrations led to the increase in free cancer cells and peritoneal fluid tumor markers: ultimately cancer recurrences developed.