OBJECTIVES: To test contemporary rates and predictors of open conversion at minimally invasive partial nephrectomy (MIPN: laparoscopic or robotic partial nephrectomy). MATERIALS AND METHODS: Within the National Inpatient Sample database (2008-2015) we identified all MIPN patients and patients that underwent open conversion at MIPN. First, estimated annual percentage changes (EAPC) tested temporal trends of open conversion. Second, univariable and multivariable logistic regression models predicted open conversion at MIPN. All models were weighted and adjusted for clustering, as well as all available patient and hospital characteristics. RESULTS: Of 7649 MIPN patients, 287 (3.8%) underwent open conversion. The rates of open conversion decreased over time (from 12 to 2.4%; EAPC: 24.8%; p = 0.004). In multivariable logistic regression models predicting open conversion, patient obesity achieved independent predictor status (OR:1.80; p < 0.001). Moreover, compared to high volume hospitals, medium volume (OR:1.48; p = 0.02) and low volume hospitals (OR:2.11; p < 0.001) were associated with higher rates of open conversion. Last but not least, when the effect of obesity was tested according to hospital volume, the rates of open conversion ranged from 2.2 (non obese patients treated at high volume hospitals) to 9.8% (obese patients treated at low volume hospitals). CONCLUSION: Overall contemporary (2008-2015) rate of open conversion at MIPN was 3.8% and it was strongly associated with patient obesity and hospital surgical volume. In consequence, these two parameters should be taken into account during preoperative patients counselling, as well as in clinical and administrative decision making.

Cancer Prognostics and Health Outcomes Unit Division of Urology University of Montreal Health Center Montreal Quebec Canada

Cancer Prognostics and Health Outcomes Unit Division of Urology University of Montreal Health Center Montreal Quebec Canada; Department of Urology and Division of Experimental Oncology URI Urological Research Institute IRCCS San Raffaele Scientific Institute Milan Italy

Cancer Prognostics and Health Outcomes Unit Division of Urology University of Montreal Health Center Montreal Quebec Canada; Department of Urology European Institute of Oncology IRCCS Milan Italy

Cancer Prognostics and Health Outcomes Unit Division of Urology University of Montreal Health Center Montreal Quebec Canada; Department of Urology San Luigi Gonzaga Hospital University of Turin Turin Italy

Cancer Prognostics and Health Outcomes Unit Division of Urology University of Montreal Health Center Montreal Quebec Canada; Department of Urology University Hospital Frankfurt Frankfurt Am Main Germany

Cancer Prognostics and Health Outcomes Unit Division of Urology University of Montreal Health Center Montreal Quebec Canada; Martini Klinik University Medical Center Hamburg Eppendorf Hamburg Germany

Department of Urology and Division of Experimental Oncology URI Urological Research Institute IRCCS San Raffaele Scientific Institute Milan Italy

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Weill Cornell Medical College New York NY USA; Department of Urology University of Texas Southwestern Dallas TX USA; Department of Urology 2nd Faculty of Medicine Charles University Prag Czech Republic; Institute for Urology and Reproductive Health 1 M Sechenov 1st Moscow State Medical University Moscow Russia

Department of Urology European Institute of Oncology IRCCS Milan Italy

Department of Urology European Institute of Oncology IRCCS Milan Italy; Department of Oncology and Hemato Oncology University of Milan Milan Italy

Department of Urology IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico University of Milan Milan Italy

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