Previous retrospective research associated signet ring cell histology with poor oncologic outcomes in colon cancer patients. However, potential bias can not be ruled out in previous studies. This is the first propensity-score based investigation assessing the prognostic impact of signet ring cell histology on overall and cancer-specific survival in patients with stage I and II colon cancer.
Stage I and II colon cancer patients undergoing surgery between 2004 and 2013 were identified in the Surveillance, Epidemiology, and End Results (SEER) database. Overall survival (OS) and cancer-specific survival (CSS) were assessed using risk-adjusted Cox proportional hazards regression models and propensity score methods.
Overall, 75,134 stage I-II colon cancer patients were included, of which 380 (0.5%) with signet ring cell histology. In unadjusted analyses, the 5-year OS and CSS in patients with signet ring cell histology was 64.7% (95% confidence interval (CI): 59.3-70.6%) and 84.1% (95% CI: 79.9-88.6%) compared with 73.9% (95% CI: 73.6-74.3%) and 88.6% (95% CI: 88.3-88.9%), respectively, in patients with non-signet ring adenocarcinoma (P = 0.003 and P = 0.026). The survival disadvantage disappeared in risk-adjusted Cox proportional hazard regression analysis (OS: hazard ratio (HR) = 0.96, 95% CI: 0.80-1.15, P = 0.647; CSS 0.88, 95% CI: 0.66-1.17, P = 0.368), and after propensity score matching (OS: HR= 0.92, 95% CI: 0.76-1.11, P = 0.357 and CSS: HR = 0.86, 95% CI: 0.65-1.16, P = 0.315).
This is the first propensity-score adjusted population-based investigation on exclusively stage I and II colon cancer patients providing compelling evidence that signet ring cell histology does not negatively impact survival. Therefore, standard treatment strategies can be applied in these patients.
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All authors have declared no conflicts of interest.