MP33-05: Diagnostic Parameters of ^99mTc-sestamibi SPECT/CT for Renal Oncocytomas and Hybrid Oncocytic/Chromophobe Tumors: Combined Prospective Trial Data

Alexa Meyer*, Hiten Patel, Lilja Solnes, Reema Goel, Mehrbod Javadi, Phillip Pierorazio, Christian Pavlovich, Mohamad Allaf, Michael Gorin, Steven Rowe, Baltimore, MD

Introduction: Previously, we reported the results of our prospective trial of 50 patients imaged with 99mTc-sestamibi SPECT/CT prior to surgical resection, and showed that 99mTc-sestamibi SPECT/CT can aid in the differentiation of benign renal oncocytomas and hybrid oncocytic/chromophobe tumors (HOCTs) from other renal tumor histologies. Here, we present the following 75 patients in the prospective trial cohort. The objective of this study was to determine the diagnostic performance of this imaging test using data from the overall cohort.

Methods: Patients presenting with a solid T1 renal mass were imaged with 99mTc-sestamibi SPECT/CT prior to surgery. For the new 75 patients in the cohort, SPECT/CT scans were analyzed by two readers, and discrepancies were resolved by a third reader. Tumors were characterized as positive (i.e. “hot”) or negative (i.e. “cold”). Radiotracer uptake was quantified. Following surgical resection, the cases were reviewed by genitourinary pathologists. Diagnostic parameters were calculated for the novel patients, as well as for the overall cohort. True positive was defined as any tumor diagnosed as an oncocytoma or HOCT following surgical resection.

Results: In total, 125 patients were enrolled in the trial. 1 tumor was non-diagnostic on imaging secondary to bowel overlying the tumor, and was excluded from analysis. In the novel 74 patients, 99mTc-sestamibi SPECT/CT correctly identified 9/12 oncocytomas and HOCTs, resulting in sensitivity of 75.0% (95% CI 42.8-94.5). 10 tumors were false positives (FP), resulting in specificity of 83.9% (95% CI 72.3-92.0). These included 5 papillary renal cell carcinomas (RCC), 3 chromophobe RCC, 1 low grade RCC with oncocytic features, and 1 angiomyolipoma. The positive predictive value (PPV) was 47.4% (95% CI 24.4-71.1) and negative predictive value (NPV) was 94.5% (84.9-98.9%). For the combined cohort of 124 patients, 99mTc-sestamibi SPECT/CT correctly identified 16/20 oncocytomas and HOCTs, resulting in sensitivity of 80.0% (95% CI 56.3-94.3). 12 tumors were FP, resulting in specificity of 88.5% (95% CI 80.7-93.9). The additional 2 FP were chromophobe RCC. The overall PPV was 57.1% (95% CI 37.2-75.5) and NPV was 95.8% (89.7-98.9%).

Conclusions: Data from this prospective trial shows that 99mTc-sestamibi SPECT/CT can aid in the risk stratification of small renal masses. A “hot” 99mTc-sestamibi SPECT/CT should proceed to biopsy for further work-up. A “cold” 99mTc-sestamibi SPECT/CT can avoid biopsy and proceed directly to surgery.

Source of Funding: none