- Design
- Systematic review and diagnostic meta-analysis
- Population
- 20 studies of preoperative MRI in histologically proven renal cell carcinoma
- Primary outcome
- Accuracy for WHO/ISUP high-grade disease
- Effect
- ADC sensitivity 0.84 (0.77–0.89), specificity 0.57 (0.51–0.63), AUC 0.71; radiomics AUC 0.90
This meta-analysis included 20 studies of quantitative MRI for predicting WHO/ISUP grade in renal cell carcinoma before surgery; 12 contributed to pooled estimates.
In seven apparent diffusion coefficient studies, sensitivity for high-grade disease was 0.84 (95% CI 0.77 to 0.89) but specificity only 0.57 (0.51 to 0.63), with a summary AUC of 0.71. Low-grade tumours had higher ADC by 0.21 × 10⁻³ mm²/s on average. Five MRI-inclusive radiomics or deep-learning studies performed better (sensitivity 0.79, specificity 0.86, AUC 0.90), but were heterogeneous and few were externally validated.
In practice, a low ADC in a solid renal mass raises the possibility of higher grade and may support biopsy over surveillance in a small mass, but a high false-positive rate means it cannot stand alone. Radiomics is not ready for routine reporting.
- Report ADC in solid renal masses on MRI, but do not grade a tumour on it.
- Treat a low ADC as one reason to favour biopsy over surveillance in a small renal mass.
- Recommend biopsy when grade would change management; imaging cannot replace it.
- Do not quote radiomics grading outputs in reports until a model is externally validated.
Why it matters
Pre-operative grade estimation matters most in small masses where surveillance is an option.
Don't overread it
The better radiomics performance comes from five heterogeneous, mostly unvalidated studies.
The statistics, in plain English
Specificity of 0.57 means that of every 100 low-grade tumours, about 43 would be wrongly flagged as high grade. Sensitivity of 0.84 means about 16 in 100 high-grade tumours would be missed.
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