A multidisciplinary evaluation of inter-reviewer agreement of the nephrometry score and the prediction of long-term outcomes

Purpose: The nephrometry score was introduced in 2009 as a way to quantify renal tumor complexity in a systematic way. However, the reproducibility of scoring has not been rigorously validated across specialty or level of training, nor has it been evaluated with regard to meaningful clinical outcomes.

Materials and methods: We identified 95 consecutive patients with a solid renal mass treated surgically. Each renal tumor was separately scored by 6 reviewers, including 2 staff urologists, 1 staff radiologist, 2 trainees (1 urology, 1 radiology) and 1 medical student. Inter-reviewer agreement for nephrometry score was evaluated using Lin's concordance correlation coefficient. We evaluated the ability of the nephrometry score to predict surgery type, pathological features and clinical outcomes.

Results: Agreement in nephrometry score was substantial among the 3 staff physicians (0.72, 95% CI 0.64-0.80). Nephrometry score agreement continued to be substantial when including the trainees and medical student in the analysis (0.75, 95% CI 0.69-0.81). The median nephrometry score of patients treated with radical nephrectomy was 9.0 vs 7.2 for those treated with a nephron sparing approach (p <0.001). Increasing nephrometry score was associated with increased risk of distant metastasis (HR 3.27, p <0.001), death from renal cell carcinoma (HR 2.83, p <0.001) and death from any cause (HR 1.24, p = 0.017).

Conclusions: Nephrometry scoring with minimal initial instruction was robust across specialties and levels of training. The additional anatomical information that nephrometry score adds to size alone may be associated with other important clinical outcomes such as tumor aggressiveness and survival, and warrants further study.