A Predictive Model for Kidney Failure After Nephrectomy for Localized Kidney Cancer: The Kidney Cancer Risk Equation

Rationale & Objective Nephrectomy is the mainstay of treatment for individuals with localized kidney cancer. However, surgery can potentially result in the loss of kidney function, or in kidney failure requiring dialysis/kidney transplantation. There are currently no clinical tools available to pre-operatively identify which patients are at risk of kidney failure over the long term. The aim of our study was to develop and validate a prediction equation for kidney failure after nephrectomy for localized kidney cancer. Study Design Population-level cohort study. Setting & Participants Adults (n=1,026) from Manitoba, Canada who were diagnosed with non-metastatic kidney cancer between January 1, 2004, and December 31, 2016, were treated with either a partial or radical nephrectomy, and had at least 1 estimated glomerular filtration rate (eGFR) measurement pre- and post-nephrectomy. A validation cohort including individuals in Ontario (n=12,043) with a diagnosis of localized kidney cancer between October 1st, 2008, and September 30th, 2018, who received a partial or radical nephrectomy, and had at least 1 eGFR measurement before and following surgery. New Predictors & Established Predictors Age, sex, eGFR, urinary albumin-creatinine ratio (urine ACR), history of diabetes mellitus, and nephrectomy type (partial/radical). Outcomes The primary outcome was a composite of dialysis, transplantation, or an eGFR <15 mL/min/1.73m2 during the follow-up period. Analytical Approach Cox proportional hazards regression models evaluated for accuracy using area under the receiver operating characteristic curve (AUC), Brier scores, calibration plots, and continuous Net Reclassification Improvement. We also implemented decision curve analysis. Models developed in the Manitoba cohort were validated in the Ontario cohort. Results In the development cohort, 10.3% reached kidney failure after nephrectomy. The final model resulted in a 5-year area under the curve of 0.85 (0.78 - 0.92) in the development cohort and 0.86 (0.84 - 0.88) in the validation cohort. Limitations Further external validation needed in diverse cohorts. Conclusions Our externally validated model can be easily applied in clinical practice to inform pre-operative discussions about kidney failure risk in patients facing surgical options for localized kidney cancer.