Long-term prognostic value of positive peritoneal washing in colon cancer

Background: We examined the potential prognostic value of free malignant ce lls in the peritoneal cavity of patients with colon adenocarcinoma. Methods : In 1991 and 1992, 88 patients underwent peritoneal washing with cytologic analysis immediately before elective colon resection for adenocarcinoma wi th no evidence of peritoneal metastases. Peritoneal washing fluid was colle cted before abdominal exploration, centrifuged immediately, and stained wit h the May-Grunwald-Giemsa and Harris Shorr methods. Malignancy was defined as recommended by Papanicolaou. Results: Free malignant cells in peritoneal fluid (positive peritoneal washing) were found in 25 of 88 (28%) patients (Dukes A, 0 of 11; Dukes B, 10 of 31; Dukes C, 11 of 37; Dukes D, 4 of 9). The positivity rate was 24 of 75 (32%) among patients with rumours involvin g the serous layer and 1 of 13 (8%) among the others (P = 0.0989). With a f ollow-up of 66.7 to 78.7 months the 5-year survival rates were 48% (95% con fidence interval, 28.4-67.6) and 68% (95% CI, 56.2-79.8) among patients wit h positive and negative peritoneal washing, respectively (P = 0.09). Positi ve peritoneal washing was not significantly associated with survival in mul tivariate analysis. Conclusion: The presence of free malignant cells in the peritoneal cavity of patients with colon cancer provided no further progno stic information relative to the Dukes classification in this study. Nevert heless, further study is needed, particularly in a larger series of Dukes B patients, for whom a new prognostic factor would be useful for deciding ad juvant therapy.