Predicting the risk of pT3a stage in cT1 clear cell renal cell carcinoma

We hypothesized that pT3a stage at nephrectomy can be accurately predicted in cT1N0M0 clear cell-renal cell carcinoma (cc-RCC) patients. Of 236 patients, treated with either partial or radical nephrectomy (2005-2019), 25 (10.6%) harbored pT3a stage. Multivariable logistic regression models predicting pT3a were fitted using age, tumor size, tumor location and exophytic rate. The new model was 81% accurate. In calibration plots, minimal departures from ideal prediction were recorded. In decision curve analyses, a net-benefit throughout all threshold probabilities was recorded relative to the treat-all or treat-none strategies. Using a probability cut-off of 21% for presence of pT3a stage, 38 patients (16.1%) were identified, in whom pT3a rate was 36.8%. Conversely, in 198 patients (83.9%) below that cut-off, the rate of pT3a was 5.6%. Alternative user-defined cut-offs may be selected. The new model more accurately identifies a subgroup of cT1N0M0 cc-RCC patients with substantially higher risk of pT3a stage than average.