Results
Among the 46,313 patients described in the database, 1405 were included in this study (427 patients in the low-volume group, 396 patients in the mid-volume group and 582 patients in the high-volume group). The flow diagram of recruitment and exclusion is illustrated in Figure 1. The median follow-up time was 30 months (interquartile range, 19·0-45·0). The clinicopathologic characteristics of the three groups are provided in Table 1. The patients in the high-volume group were more likely to have LVSI (P = 0·004) and lymph node metastasis (P = 0·002); those in the mid- and high-volume groups were more likely to have deep stromal and uterine invasion than were those in the low-volume group (all P < 0·05).