Aims: Studies on the value of peritoneal tumour cell dissemination for prognosis in gastric cancer using various methods to detect tumour cells have produced conflicting conclusions. We studied the incidence and prognostic relevance of microscopic intraperitoneal tumour cell dissemination in gastric cancer, comparing conventional and immunocytological detection.
Methods: Peritoneal wash-outs of 111 consecutive gastric patients without overt peritoneal carcinomatosis, including 75 curatively resected patients, were studied. Sixty patients with benign disorders served as controls. 100 ml of warm NaCl 0.9% was instilled intraoperatively and 20 ml was reaspirated. The specimens were stained peri-operatively with H&E. In the last 47 patients (30 of whom were curatively resected) additional immunostaining with the HEA-125 antibody was performed. The results of cytology were correlated with the TNM categories and with post-operative follow-up.
Results: Of the patients, 42.3% and 48.9% were positive when conventional and immunocytological staining were employed, respectively. Conventional cytology was significantly associated with the pT and M categories. Immunocytology was significantly associated with the pT, pN and M caterogies. In four of 30 curatively resected patients (13.3%), the results of conventional and immunocytology were different. Three patients with positive immunocytology but negative conventional cytology died during follow-up (median follow-up 45.3 months), whereas one patient with positive conventional but negative immunocytology is still alive. In an univariate analysis 4 years post-surgery, positive immunocytology was significantly associated with an unfavourable prognosis in patients with curatively resected gastric cancer. While only 28.6% (six of 21) of the patients with negative immunocytology had died, this proportion increased to 77.8% (seven of nine) with positive immunocytology (P=0.018). The mean survival of negative vs positive patients amounted to 1205+/-91 vs 772+/-147 days (P=0.007). In contrast, in conventional cytology we found no significantly different survival time between negative and positive patients.
Conclusions: Immunocytology seems to be superior to conventional cytology and should be preferred.