Performance of Tc-Sestamibi Single-Photon Emission Computed Tomography/Computed Tomography for Characterizing Renal Masses: Combined Results From a Prospective Scan-and-Resect Trial and Clinical Experience

Purpose: Anatomic imaging and biopsy have limitations in the risk stratification of indeterminate renal masses. Molecular imaging offers opportunities to improve noninvasive risk stratification. Tc-sestamibi is a mitochondrial imaging agent that has shown increased uptake in benign/indolent renal tumors and a lack of uptake in aggressive renal cell carcinomas (RCCs). Materials and methods: We evaluated the accuracy of Tc-sestamibi single-photon emission CT (SPECT/CT) imaging to characterize histologically diagnosed renal masses using 2 cohorts of patients; one from a prospective scan-and-resect clinical trial and a second from routine clinical care. The rate of renal mass positivity (ie, "hot tumors") on Tc-sestamibi SPECT/CT was stratified by histology. Diagnostic performance to identify histologic groupings of interest was measured by sensitivity and specificity. Results: Three hundred forty-four patients with 361 tumors (124 trial, 237 clinical) were included. Most clear cell RCC (97%) and papillary or clear cell papillary RCC (80%-84%) were cold while chromophobe RCCs were equally likely to be hot or cold (52% vs 48%). Surgically resected oncocytomas tended to be hot (69%), with even higher positivity for biopsy with oncocytic neoplasms in the clinical cohort (87%). Limitations included the heterogeneous nature of the cohort and the use of biopsy for histologic diagnosis in the clinical cohort. Conclusions: Tc-sestamibi SPECT/CT is a novel method to effectively risk-stratify indeterminate renal masses. As with any nonsurgical method for renal mass characterization, there are potential false positives and false negatives, and those should be weighed carefully in shared decision-making with the patient to guide further evaluation and management.