Prospective Evaluation of ^99mTc-MIBI SPECT/CT for the Diagnosis of Solid Renal Tumors

Objectives: The differentiation of benign renal tumors from renal cell carcinomas (RCCs), such as oncocytoma or fat-poor angiomyolipoma, remains a conundrum with conventional cross-sectional imaging techniques. ^99mTc-MIBI SPECT/CT offers a potential noninvasive means of determining the histology of renal solid tumors. In this study, we explored the effectiveness of 99^mTc-MIBI SPECT/CT for the diagnosis of renal lesions. Patients and Methods: Patients were recruited as part of an institutional review board-approved prospective clinical trial. 30 patients with solid solitary renal lesions were imaged with ^99mTc-MIBI SPECT/CT before surgical resection. Preoperative SPECT/CT scans were reviewed by two blinded readers, and their results were compared with reviewed surgical histopathology. Following pathology data, 3(10%) tumors were classified as renal oncocytomas, 1(1%) angiomyolipoma, and other tumors were all RCC (89%). Relative quantification was performed by measuring tumor-to-normal renal parenchyma background ratios.

Results: Postsurgical pathology confirmed the diagnosis of benign histology (oncocytoma/ angiomyolipoma) in 4 and 26 malignant histology (RCC). All 3 oncocytomas and 1 angiomyolipoma demonstrated radiotracer uptake near the normal renal parenchymal uptake (range of uptake ratios, 0.70-0.96). In contrast, 25 out of 26 (96%) RCCs were profoundly lower uptake (range of uptake ratios, 0.07-0.52) relative to renal background. Only one RCC (uptake ratios, 0.72) was falsely positive on SPECT/CT.

Conclusions: ^99mTc-MIBI SPECT/CT appears to be of value in distinguishing benign renal tumors from RCC. This imaging method can be used to diagnose two types of benign kidney tumors. Our experiment may be eventually used to help better evaluate patients diagnosed with a solid renal mass. In summary, ^99mTc-MIBI SPECT/CT is a promising imaging test for the noninvasive diagnosis of solid renal tumors. However, larger numbers are needed to precisely define the sensitivity and specificity of this test. Keywords: Oncocytoma, Angiomyolipoma, Renal Cell Carcinoma,^99mTc-MIBI, SPECT/CT

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