Abstract
BACKGROUND: Histological subtypes of colorectal cancer may be associated with varied prognostic features. This systematic review and meta-analysis aimed to compare clinicopathological characteristics, recurrence and overall survival between colorectal signet-ring cell (SC) and mucinous carcinoma (MC) to conventional adenocarcinoma (AC). METHODS: A literature search of MEDLINE, EMBASE, Ovid and Cochrane Library was performed for studies that reported data on clinicopathological and survival outcomes on SC and/or MC versus AC from January 1985 to May 2020. Meta-analysis was performed using random-effect models and between-study heterogeneity was assessed. RESULTS: Thirty studies of 1,087,055 patients were included: 11,510 (1.06%) with SC, 110,179 (10.13%) with MC and 965,366 (88.81%) with AC. Patients with SC were younger than patients with AC (WMD - 0.47; 95% CI - 0.84 to -0.10; I(2) 88.6%; p = 0.014) and more likely to have right-sided disease (OR 2.12; 95% CI 1.72-2.60; I(2) 82.9%; p < 0.001). Locoregional recurrence at 5 years was more frequent in patients with SC (OR 2.81; 95% CI 1.40-5.65; I(2) 0.0%; p = 0.004) and MC (OR 1.92; 95% CI 1.18-3.15; I(2) 74.0%; p = 0.009). 5-year overall survival was significantly reduced when comparing SC and MC to AC (HR 2.54; 95% CI 1.98-3.27; I(2) 99.1%; p < 0.001 and HR 1.38; 95% CI 1.19-1.61; I(2) 98.6%; p < 0.001, respectively). CONCLUSION: SC and MC are associated with right-sided lesions, advanced stage at presentation, higher rates of recurrence and poorer overall survival. This has strong implications towards surgical and oncological management and surveillance of colorectal cancer.