Differentiation of renal cell carcinoma (RCC) from oncocytoma is a common diagnostic dilemma. A number of studies have suggested that technetium- 99m (99mTc)-sestamibi SPECT/CT has the potential to characterize indeterminate renal masses. According to a study of real-world experience from Fox Chase Cancer Center – Temple Health (FCCC) in Philadelphia, however, 99mTc-sestamibi SPECT/CT is not yet ready to replace renal biopsy.1
The study reported by Avery E. Braun, DO, and colleagues in the FCCC Department of Surgical Oncology, Division of Urologic Oncology was a single-institution, retrospective review of data obtained from patients whose renal masses were characterized with 99mTc-sestamibi SPECT/CT between February 2020 and October 2021.
All scans were performed based on departmental standardized practice and interpreted by a senior nuclear radiologist. When a 99mTc-sestamibi SPECT/CT scan was positive, it was considered “hot” for oncocytic tumor. This occurred when uptake was qualitatively equivalent between the mass of interest and normal renal parenchyma, suggestive of oncocytoma, hybrid oncocytic/ chromophobe tumor (HOCT), or chromophobe RCC. A negative 99mTc-sestamibi SPECT/CT scan was considered “cold” if dropout of signal was observed between the mass and renal parenchyma, which was suggestive of RCC.
Demographic and pathologic data were collected and compared between patients with positive/” hot” and negative/” cold” scans and between management strategies. For patients who subsequently underwent definitive surgical intervention, radiographic findings were compared against final surgical pathology.
By October 2021, 59 patients with a total of 76 renal masses had undergone 99mTc-sestamibi imaging. Sixteen (21.1%) masses were defined as “hot” and 60 (78.9%) were defined as “negative” i.e., consistent with RCC.
On review of demographics, younger age at diagnosis (70.6 vs 76.4 years, P=0.033) and sex (P=0.048) were associated with a negative/”cold” 99mTc-sestamibi image, while patient race and history of diabetes or hypertension were not. In addition, none of the mass characteristics evaluated, including laterality, size, and RENAL nephrometry score, and clinical stage, was associated with positive/ “hot” or negative/ “cold” scans.
Review of management decisions based on scan findings showed that 10 positives/ “hot” scans led to active surveillance and 4 to biopsy. Three biopsy results were concordant with preoperative imaging and consistent with chromophobe RCC (1) or oncocytoma (2), and 1 was discordant with preoperative imaging and was associated with clear cell RCC. Of the 60 patients with negative/”cold” scans, 14 opted for active surveillance, 3 in cryotherapy, and 1 systemic therapy. Five biopsies revealed discordant pathology with preoperative imaging in 3 (oncocytoma). The researchers calculated that the negative predictive value for ruling out oncocytic tumor for masses that underwent pathologic sampling was 82.6%.
Dr Braun and his colleagues concluded that based on their findings from this large institutional experience, further work is needed to define the clinical utility of 99mTc-sestamibi SPECT/CT in differentiating renal masses before it can be considered an alternative to biopsy.
David Ambinder, MD is a urology resident at New York Medical College / Westchester Medical Center. His interests include surgical education, GU oncology and advancements in technology in urology. A significant portion of his research has been focused on litigation in urology.
- Braun A, Schober J, Castro-Bigalli A, et al. Utility of technectium-99m sestamibi SPECT/CT in minimizing overtreatment of benign renal mass. Poster #85 presented at the 22nd Annual Meeting of the Society of Urologic Oncology (SUO), December 103, 2021, Orlando, FL.