Differentiation of Renal Oncocytoma From Renal Cell Carcinoma Using 99mTc-Sestamibi SPECT/CT

Background: 99mTc-Sestamibi Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) contributes to the non-invasive differentiation of renal oncocytoma (RO) from renal cell carcinoma (RCC). We investigated whether standard uptake value (SUV) SPECT, has a beneficial role in differentiating renal oncocytoma (RO) from renal cell carcinoma (RCC) besides visual assessment. As a secondary aim, we evaluated the mitochondrial content of 19 oncocytic tumours arranged in a tissue microarray, by immunohistochemistry, using succinate dehydrogenase complex subunit B (SDHB) protein expression. In addition to visual evaluation of 99mTc-Sestamibi uptake by characterizing renal tumours as Sestamibi positive or Sestamibi negative regarding their uptake compared to the non-tumoral renal parenchyma, SUVmean and SUVmax measurements were performed in the renal tumour and the non-tumoral renal parenchyma. Intra Class Correlation calculated to assess the intra-reader reliability of SUV measurements. ROC-analysis demonstrated an optimal cut off SUV value that differentiates RO from RCC. SDHB score was analysed using Cochran–Armitage test for trend.Results: 57 renal tumours from 52 patients were evaluated. Visual evaluation of 99mTc-Sestamibi SPECT/CT examination resulted in a sensitivity of 83%, whereas quantitative evaluation showed a sensitivity of 64% regarding the differential of RO from RCC. A significant trend (p=0,0328) of increased SDHB score found in the Sestamibi positive group.Conclusion: Quantitative evaluation with SUV SPECT measurements did not improve the performance of 99mTc-Sestamibi SPECT/CT in differentiating RO from RCC. 99mTc- Sestamibi SPECT/CT identified a larger Sestamibi-positive tumour group containing RO, Hybrid Oncocytic Chromophobe Tumours and the majority of chromophobe RCCs. Thus, Sestamibi-negative renal tumours, that are possibly malignant, should be considered for surgery. Patients with Sestamibi-positive tumours can be suited for biopsy and follow up according to active surveillance protocols. Low Grade Oncoytic Tumour, a provisional renal entity with no proven recurrence or metastatic potential, appears to be positive on 99mTc- Sestamibi SPECT/CT examination.