Conversions in robot-assisted partial nephrectomy: a multicentric analysis of 2549 cases.

Background: Conversion in partial nephrectomy to radical nephrectomy occurs in 1-5%. This analysis assessed predictors for conversions in robot-assisted partial nephrectomies.

Methods: Two thousand five hundred forty-nine patients at eight robotic centers for robot-assisted partial nephrectomy were retrospectively analyzed. Intervention was performed by 25 surgeons with varying expertise. Conversion was defined as change from robot-assisted partial nephrectomy to open partial, open radical or robot-assisted radical nephrectomy. Comparative analyses between converted and non-converted cases and within subgroups as well as multivariate regression analyses for predictors for conversion were performed.

Results: Eighty-eight (3.5%) conversions were documented (17% open nephrectomy, 53% open partial nephrectomy, 30% robot-assisted nephrectomy). In case of conversion, patients were significantly older (P<0.001) with a higher Body Mass Index (BMI; P=0.029), larger tumor size (P<0.001), multiple tumors (P<0.001) and higher PADUA scores (P<0.001). Converting surgeons had a significantly lower experience in RAPN (median EXP 64 vs. 29, P<0.001). The main reasons to convert were unfavorable anatomic features (69%). Radical nephrectomy occurred more frequently in tumors with higher PADUA Score (P<0.001). Experienced surgeons in open renal surgery performed more often open partial nephrectomy in case of open conversion (P<0.001). Patients' age, BMI, surgeon's expertise, number of tumors, tumor size and PADUA Score were independent predictors for conversion (P<0.001). Limitations are the retrospective study design and short-term follow-up.

Conclusions: Conversions in robot-assisted partial nephrectomy are predominantly determined by patient- and tumor-related factors, but also surgical experience. Intensified surgical training might reduce the risk of conversions with an increased chance for nephron-sparing surgery in converted cases.