PD45-01 EVALUATION AND RISK STRATIFICATION OF RENAL MASSES WITH ^99M TC-SESTAMIBI SPECT/CT

Abstract

There is significant overlap in the imaging characteristics of renal cell carcinoma (RCC) and oncocytoma, resulting in diagnostic uncertainty and unnecessary surgical resection. However, both oncocytomas and chromophobe RCC are known to be rich in mitochondria, compared to clear cell and papillary RCC subtypes. 99m Tc-sestamibi (MIBI) SPECT/CT scans localize within the mitochondria and have emerged as a potential imaging modality to further characterize renal masses. The goal of this study is to evaluate the utility of MIBI SPECT/CT imaging in the assessment and risk stratification of indeterminate renal masses.METHODS: A comparative study including 23 patients with indeterminate renal masses was performed. All patients had prior crosssectional imaging and underwent MIBI SPECT/CT imaging. MIBI SPECT/CT imaging characteristics including lesion density and MIBI uptake were correlated with histopathology from either percutaneous biopsy or surgical resection. Lesions with any degree of MIBI uptake were defined as positive and lesions with no uptake as negative (figure 1).RESULTS: 23 lesions were included with a median size of 3.2cm (1.8-6cm) and a density ranging from 22 to 56 Hounsfield Units. 20 of the lesions were solid enhancing masses and 3 were Bosniak 4 complex cysts with measurable solid components. Biopsy or postsurgical histopathology demonstrated 5 oncocytomas, 1 hybrid oncocytic/chromophobe tumor (HOCT) and 17 RCCs including 13 clear cell, 2 papillary and 1 chromophobe subtype. The median of mean and maximum relative tumor uptake in MIBI positive tumors (oncocytomas and HOCT) was 0.80 and 0.85, compared to 0.30 and 0.30 in cases with RCC, respectively. Using a mean relative tumor uptake of 0.5, all patients with oncocytoma and HOCT (100%) had positive MIBI uptake, and all RCC patients (0%) were negative.CONCLUSIONS: This study contributes to the growing literature indicating that MIBI uptake is a distinguishing imaging feature of low risk renal masses. The combination of presence or absence of MIBI uptake and lesions' density on SPECT-CT represents a novel imaging approach to risk stratifying incompletely characterized renal masses. Further validation of this technique may reduce the need for further imaging and unnecessary biopsy or surgical resection of indeterminate renal masses.

Renal oncocytoma: landscape of diagnosis and management

“…The poor uptake of renal tumour biopsy highlights the need for improved diagnostics of benign renal tumours that are accurate and acceptable to patients and clinicians alike. Technetium (99 m Tc)-sestamibi single-photon emission CT (SPECT)/CT has shown promise in small trials in the USA and Sweden in distinguishing benign oncocytoma from RCC [7][8][9]. 99 m Tc-sestamibi is a radiotracer preferentially taken up by cells with abundant mitochondria such as oncocytoma, and actively transported out of cells in RCCs.…”