Predictors of lymph node metastasis and prognosis in early colorectal cancer patients with signet-ring cell and mucinous adenocarcinomas.

Abstract

717 Background: The local excision of early colorectal cancer is limited by the presence of lymph node metastasis. Signet-ring cell carcinomas and mucinous adenocarcinomas are two relatively infrequent histological subtypes. However, little is known about the predictors of lymph node metastases and prognosis to support the feasibility of local excision in early-stage signet-ring cell and mucinous colorectal adenocarcinomas. Methods: The Surveillance Epidemiology and End Results Database (1988 to 2006) from the National Cancer Institute was used to identify all patients with T1 adenocarcinomas, including conventional adenocarcinoma (AC), mucinous adenocarcinomas (MAC), and signet-ring cell carcinoma (SRC). The prevalence of lymph node metastasis was assessed, and the long-term survival rate in the above three types of colorectal cancer was calculated. Results: Final cohorts of 47,260 patients were eligible for analysis. SRC accounted for 0.3% and MAC accounted for 3.7% of the entire cohort of colorectal adenocarcinomas. Compared to AC, SRC and MAC more frequently presented at a younger age, were located in the proximal colon, and exhibited a higher grade. The incidence of lymph node metastasis in AC, MAC, and SRC was 5.8%, 10.8%, and 15.3%, respectively. Patients with SRC were associated with a worse prognosis, regardless of the tumor location. Patients with MAC of the rectum, but not the colon, were associated with a reduced implication of prognosis. After adjusting for other clinicopathological factors, SRC and MAC of the rectum were independently associated with a high risk of death (HR 2.70, CI 1.77-4.12 and HR 1.65, CI 1.38-1.98 for SRC and MAC, respectively). Histology was not found to be an independent prognostic factor in patients with colon cancer. Conclusions: MAC and SRC are two distinct subtypes of colorectal cancer that require special attention despite their relatively rare prevalence. T1 patients with SRC and patients with MAC of the rectum have higher incidences of lymph node metastasis (LNM), and with these adverse outcomes, local excision is not recommended. Although MAC of the colon has a high rate of LNM, the prognosis of this type is similar to that of AC.