Diagnostic performance of CT for extrarenal fat invasion in renal cell carcinoma: a meta-analysis and systematic review

Abstract Objectives Renal cell carcinoma (RCC) with extrarenal fat (perinephric or renal sinus fat) invasion is the main evidence for the T3a stage. Currently, computed tomography (CT) is still the primary modality for staging RCC. This study aims to determine the diagnostic performance of CT in RCC patients with extrarenal fat invasion. Methods The PubMed, Web of Science, Cochrane Library, and EMBASE databases were systematically searched up to October 11, 2023. Study quality was assessed by the QUADAS-2 tool. Standard methods recommended for meta-analyses of diagnostic evaluation were used. Heterogeneity was analyzed through meta-regression analysis. Results Fifteen studies were included in this meta-analysis. Among them, six studies focused on perinephric fat invasion (PFI) only, four on renal sinus fat invasion (RSFI) only, and five on both. Pooled weighted estimates of sensitivity, specificity, area of SROC curve, PLR, and negative likelihood ratio (NLR) of CT for PFI were 0.69 (95% CI: 0.55–0.79), 0.82 (95% CI: 0.69–0.90), 0.81 (95% CI: 0.77–0.84), 3.85 (95% CI: 2.22–6.67), and 0.38 (95% CI: 0.27–0.55). Pooled weighted estimates of sensitivity, specificity, area of SROC curve, PLR, and NLR of CT for RSFI were 0.81 (95% CI: 0.76–0.85), 0.79 (95% CI: 0.66–0.88), 0.82 (95% CI: 0.78–0.85), 3.91 (95% CI: 2.26–6.77), and 0.24 (95% CI: 0.18–0.31). Conclusion CT has the ability to detect the PFI and RSFI in patients with RCC. However, the diagnostic performance of CT has suffered from the limitation of slightly lower accuracy, resulting from the low positive sample in the current studies. Additionally, the current PLR is low. Critical relevance statement This study provides radiologists and urologists with a systematic and comprehensive summary of CT and CT-related morphological features in assessing extrarenal fat invasion in patients with RCC. Key Points CT can detect extrarenal fat invasion in patients with RCC, but the diagnostic performance is inconsistent. The diagnostic performance of CT is acceptable, but primarily affected by the low positive rate of included patients. Further large-scale trials are necessary to determine the true diagnostic capabilities of CT for extrarenal fat invasion. Graphical Abstract