2.2. Data Extraction

In the search and review, 13 eligible studies were finally included [4,12,13,14,15,16,17,18,19,20,21,22,23]. The extracted data from the eligible studies were the author’s information, publication year, study location, number of patients analyzed, the prevalence and the clinicopathological characteristics of ITB, the correlation with various markers, and the information for disease-free survival. For the quantitative aggregation of the survival results, the correlation of disease-free survival between CRC with ITBs and CRC without ITBs was analyzed according to the hazard ratio (HR) using one of two methods. In studies that did not record the HR or confidence interval (CI), we calculated these variables using the HR point estimate, the log-rank statistic or its p-value, and the O-E statistic (the difference between the number of observed and expected events) or its variance. If these data were unavailable, the HR was estimated using the total number of events, the number of patients at risk in each group, and the log-rank statistic or its p-value. The published survival curves were read independently by two authors to reduce variability. The HRs were then combined using Peto’s method [24]. All data were obtained by two independent authors (Kang G.H. and Pyo J.S.).