Prognostic significance of peritoneal lavage cytology in patients with colorectal cancer

Abstract

The clinical significance of peritoneal lavage cytology for patients with gastric cancer is recognized, whereas that for patients with colorectal cancer remains controversial. The present study used a nationwide registry to clarify the prognostic significance of peritoneal lavage cytology in patients with colorectal cancer. We retrospectively analyzed factors associated with recurrence and survival in patients with T3-T4 colorectal cancer without distant metastasis taken from the nationwide registry of the Japanese Society for Cancer of the Colon and Rectum between 1984 and 1999. Among 34,554 patients in this study, not all of whom received peritoneal lavage cytology, 35 had positive peritoneal lavage cytology. Gender (P = 0.0004), tumor location (P < 0.0001), histological grade (P < 0.0001), depth of tumor invasion (P < 0.0001), lymph node metastasis (P < 0.0001) and peritoneal cytology (P = 0.015) were risk factors for peritoneal recurrence. Multivariate analysis revealed that tumor location (P < 0.0001), histological grade (P < 0.0001), depth of tumor invasion (P < 0.0001) and lymph node metastasis (P < 0.0001) were independent risk factors for peritoneal metastasis. Gender (P < 0.0001), tumor location (P < 0.0001), age (P < 0.0001), histological grade (P < 0.0001), depth of tumor invasion (P < 0.0001), lymph node metastasis (P < 0.0001) and peritoneal cytology (P = 0.0004) were independent prognostic factors according to the Cox proportional hazards model. Positive peritoneal lavage cytology was associated with poorer survival in patients with stage II and III colorectal cancer. Positive cytology might be a good indicator of candidates for intensive adjuvant chemotherapy. The benefit of intensive adjuvant chemotherapy for such patients should be validated in prospective trials.