Rationale: To assess the diagnostic accuracy of 99mTc-Sestamibi SPECT/CT for characterizing solid renal masses. Methods: Imaging and clinical records of patients who underwent 99mTc-Sestamibi SPECT/CT for clinical work-up of their solid renal masses, from September 2018 to October 2021 were retrospectively reviewed. Histopathology (sample from biopsy/ surgery) formed the reference standard. The histopathologic diagnoses were segregated as malignant/concerning (RCCs other than chromophobe histology) and benign/non-concerning (oncocytic renal neoplasms including chromophobe RCC, other benign diagnoses) to calculate the sensitivity and specificity of 99mTc-Sestamibi SPECT/CT and contrast-enhanced CT (ceCT). The clinical reads of the SPECT/CT images were used for the visual classification of the lesions. Additionally, the images were manually segmented to obtain maximum and mean counts of the lesion, adjacent renal cortex, and maximum and mean lesional HU. Results: 99mTc-Sestamibi SPECT/CT was performed in 42 patients to evaluate their 62 renal masses. A histopathologic diagnosis was available in 27 patients (mean age 66.8±10.4 years; 18 men, 9 women), with 36 solid renal masses. ceCT findings were available in 20 of these patients. The most commonly identified single histology was clear-cell RCC (13/36; 36.1%). Oncocytic tumors were the most common group of non-concerning lesions (15/36) with oncocytoma as the predominant histology (n = 6). The sensitivity and specificity of SPECT/CT for diagnosing a non-concerning lesion was 66.7%, and 89.5% respectively, compared to 10%, and 75% for ceCT, respectively. Lesion to kidney count ratios could be calculated for 31 lesions. The lesion to kidney ratios for maximum and mean counts, and maximum lesion HU showed significant differences between the two groups (P<0.05). Lesion to kidney mean count ratio at a cut-off value of >0.46 showed a sensitivity and specificity of 87.5%, and 86.67% respectively for detecting non-concerning lesions which was significantly higher than that of ceCT. The highest area under the curve of 0.92 was obtained by retrospectively combining maximum HU and mean lesion-to-kidney count ratio on SPECT/CT. Conclusion: The current literature on the utility of 99mTc-Sestamibi SPECT/CT for characterization of solid renal masses is limited. We offer additional evidence on the incremental value of 99mTc-Sestamibi SPECT/CT over ceCT for differentiating the malignant/aggressive renal tumors from the benign/indolent ones, thereby potentially avoiding over-treatment and its associated complications. Quantitative assessment can further increase the diagnostic accuracy of SPECT/CT and may be used in conjunction with the visual interpretation.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2022 Jun 30 [Epub ahead of print]
Ashwin Singh Parihar, Joyce Mhlanga, Carrie Ronstrom, Lisa R Schmidt, Robert S Figenshau, Farrokh Dehdashti, Richard L Wahl
Washington University School of Medicine, United States.