Impact of expert centers annual case volume on outcomes of minimally-invasive liver resections: international multicenter study

Abstract

Background: Presently, evidence on the volume-outcome relationship for minimally-invasive liver resections (MILR) remains heterogeneous. This study aimed to investigate the volume-outcome relationships in expert centers which had already mounted the initial learning curve of MILR and had a case volume of >20 MILR/annum. Methods: This was an international multicenter retrospective analysis of 22,210 patients undergoing MILR between 2015 and 2022 at 64 centers. Centers were stratified into medium volume (MV), high volume (HV) and very high volume (VHV) defined as 20-50/51-80 and >80 MLR/annum. Difficulty of resections was graded according to the Iwate score and Institute Mutualiste Montsouris (IMM) system. Results: A total of 19,691 MILR met study criteria and were included. Of the 19,961 patients, 4,747 (2 5.6%), 4,222 (23.8%) and 10,243 (50.7%) were performed in 28 MV, 15 HV and 17 VHV centers, respectively. In the overall IMM I and IMM III cohorts, open conversion rates were consistently significantly higher in MV centers. Significantly, in the subgroup analysis of IMM 3 MILR, the VHV cohort had less blood loss [>500 mL: 443.7 (19.6%) vs. 221.6 (22.1%) (MV) vs. 296.9 (26.0%) (HV), P=0.001], shorter operative times [292 vs. 362.7 (MV) vs. 372.9 (HV) min, P<0.001] and shorter postoperative stay [7.8 vs. 8.3 (MV) and 10 (HV) days, P<0.001]. However, the HV cohort had the lower rates of open conversion [79.4 (7.0%) vs. 174.3(7.7%) (VHV) vs. 103.2 (10.3%) (MV); P=0.03]. Conclusions: Center volume-outcome relationship beyond 20 MILR/annum was not clear and results were heterogenous suggesting that factors other than center volume alone had a more significant impact on perioperative outcomes of MILR in these expert centers.