Prognostic value of microscopic peritoneal dissemination - Comparison between colon and gastric cancer

PURPOSE: We evaluated the incidence and prognostic referance of microscopic intraperitoneal tumor cell dissemination of colon cancer in comparison wit h dissemination of gastric cancer as a rational for additive intraperitonea l therapy. METHODS: Peritoneal washouts of 90 patients with colon and 111 patients wit h gastric cancer were investigated prospectively. Sixty patients with benig n diseases and 8 patients with histologically proven gross visible peritone al carcinomatosis served as controls. Intraoperatively, 100 mi of warm NaCl 0.9 percent were instilled and 20 mi were reaspirated. In all patients hem atoxylin and eosin staining (conventional cytology was performed. Additiona lly, in 36 patients with colon cancer and 47 patients with gastric cancer, immunostaining with the HEA-125 antibody (immunocytology) was prepared. The results of cytology were assessed for an association with TNM category and cancer grade, based on all patients, and with patient survival among the R O resected patients. RESULTS: In conventional cytology 35.5 percent (32/90) of patients with colon cancer and 42.3 percent (47/111) of patients with g astric cancer had a positive cytology. In immunocytology 47.2 percent (17/3 6) of patients with colon cancer and 46.8 percent (22/47) of patients with gastric cancer were positive. In colon cancer, positive conventional cytolo gy was associated with pT and M category (P = 0.044 and P = 0.0002), wherea s immunocytology was only associated with M category (P = 0.007). No associ ation was found between nodal status and immunocytology in colon cancer and with the grading. There was a statistically significant correlation betwee n pT M category and conventional and immunocytology in gastric cancer (P < 0.0015/P = 0.007 and P < 0.001/P = 0.009, respectively). Positive immunocyt ology was additionally associated with pN category: (P = 0.05). In. a univa riate analysis of RO resected patients (no residual tumor), positive immuno cytology was significantly related to an unfavorable prognosis in patients with gastric cancer only (n = 30). Mean survival time was significantly inc reased in patients with gastric cancer with negative cytology compared with positive cytology (1,205 (standard error of the mean 91) vs. 771 (standard error of the mean, 147) days; P = 0.007) but not in patients with colon ca ncer (1,215 (standard error of the mean, 95) vs. 1,346 (standard error of t he mean, 106) days; P = 0.55). CONCLUSIONS: Because microscopic peritoneal dissemination influences survival time after RO resections only in patients with gastric but not with colon cancer, our results mal provide a basis fo r a decision on additive prophylactic (intraperitoneal) therapy in gastric but not colon cancer.