To compare perioperative outcomes between open conversion and planned open surgical approach and to investigate trends.

The National Cancer Database (NCDB) was queried for cT1 and cT2 RCC treated by radical (RN) or partial (PN) nephrectomy between 2010 and 2016. We retrospectively analyzed patient demographics, clinical tumor characteristics, and perioperative outcomes between unplanned open conversion and planned open approaches for RN and PN.

In total, 152,919 patients underwent RN or PN for cT1 or cT2 RCC over the 7-year span. The rate of unplanned open conversion from MIS was 3.9% overall, remaining lowest for cT1 PN (2.7%) and highest for cT2 RN (5.9%). Cases of open conversion tended to have higher rate of upstaged disease. When comparing open conversion to a planned open case, there was no difference in the length of post-operative hospitalization. On logistic regression, unplanned open conversion from MIS was associated with higher odds of positive margin for RN but not for PN. Increased odds of 30-day's readmission were associated with unplanned open conversion from MIS in the setting of cT1 PN only.

When compared to a planned open approach, conversion to open from MIS does not affect length of hospital stay but is associated with higher odds of positive surgical margins for RN and higher odds of 30-day's readmission for cT1 PN. Advanced pathologic stage is associated with an open conversion, likely relating to increased tumor complexity. These findings should be considered preoperatively when determining the best surgical approach.