Background: The phenomenon of neuroendocrine differentiation has been observed in colorectal adenocarcinoma. However, the ability of neuroendocrine differentiation to predict the outcome of colorectal adenocarcinoma remains controversial.
Methods: We conducted an extensive search of research studies related to neuroendocrine differentiation using scientific databases, including the PubMed, Embase, OVID, BIOSIS Previews, and Cochrane Central Register of Controlled Trials (up to July, 2013), according to the established search terms. RevMan version 5.2 statistical program was used to analyze the data. An odds ratio (OR) with a 95% confidence interval (CI) was used for the dichotomous data.
Results: Eleven studies with a total of 1,587 patients were included. Patients with neuroendocrine differentiation who underwent a radical operation had a lower 5-year survival rate (pooled OR 0.60, 95% CI 0.37-0.97) compared with those without neuroendocrine differentiation, with evidence of moderate heterogeneity (I (2) = 37%, p = 0.10). A sensitivity analysis and meta-regression showed that the different classification criteria of neuroendocrine differentiation used in these studies were the main source of heterogeneity. When the strong positive rates of neuroendocrine differentiation indicators between the higher (stage III + IV) and the lower (stage I + II) clinical stages were compared, the pooled OR was 1.84 (703 patients; 95% CI 0.98-3.43) without evidence of heterogeneity (I (2) = 0 %, p = 0.89). However, comparisons between consecutive stages showed different ORs: stage II vs. I (203 patients; OR = 0.52, 95% CI 0.17-1.56), stage III vs. II (569 patients; OR = 2.27, 95% CI 1.03-4.98), and stage IV vs. III (375 patients; OR = 1.81, 95% CI 1.00-3.29).
Conclusion: The patients with strong positive indicators of neuroendocrine differentiation had a lower 5-year survival rate. The ability to detect neuroendocrine indicators using conventional methods could improve the prognosis judgment of colorectal adenocarcinoma.