Oncology outcome
In 1405 cases, 48 cases died and 104 cases recurred. The clinicopathologic characteristics of the two groups are shown in Table 1. in the low-, mid- and high-volume groups ,the 5-year DFS was 92·0%, 87·5% and 87·6%; the 5-years OS was 96·1%, 93·1% and 92·5%; there was no significant difference between the three groups (DFS: P=0·215; OS: P = 0·155)· The Kaplan–Meier survival curves are shown in Figures 2· In the multivariable analysis, adjusting for the case mix, patients in different volume groups were not an independent worse prognostic factor for a worse 5-year DFS or OS (DFS: p=0·508;OS: p=0·353, Table 2)
After 1:1 PSM between each two of the three groups, the clinicopathological characteristics were well balanced (Table 3). ① For the low group vs the mid group, including 254 patients in each, there was no significant difference in 5-year DFS or OS (DFS: 90·0% vs 91·6%, P = 0·729; OS: 94·3% vs 93·8%; P = 0·137). In Cox regression analysis adjusting for the above factors, the volume of surgery was not an independent risk factor for DFS and OS (DFS: P = 0·489; OS: P = 0·131). ② There was also no significant difference in OS and DFS between the low and high groups, including 218 patients in each (DFS: P = 0·651, OS: P = 0·474). After eliminating the case mix factors by Cox regression analysis, the volume of surgery was not an independent risk factor for DFS and OS (DFS: P = 0·289; OS: P = 0·583). ③ Between the mid and high groups, with 444 patients in each. there was no significant difference in DFS and OS (DFS: P = 0·754; OS: P = 0·788). After eliminating the case mix factors by Cox regression analysis, the surgical volume of surgeons was not an independent risk factor for DFS and OS (DFS: P = 0·598; OS: P = 0·959).