Evaluation of [99mTc]Tc-HYNIC-PSMA-11 avidity in subtypes of renal cell carcinoma tumors

Renal cell carcinoma (RCC) is one of the most lethal urologic malignancies. The role of prostate-specific membrane antigen (PSMA) in prostate cancer is well known. PSMA has been shown in other tumors including renal cell carcinoma. [99mTc]Tc-HYNIC-PSMA-11 SPECT/CT is known as a cost effective alternative to [68Ga]Ga-PSMA in prostate cancer. We prospectively evaluated the bio-distribution and diagnostic role of 99mTc-HYNIC-PSMA SPECT/CT in patients with renal tumors before surgery; and also investigated whether the intensity of Tc-PSMA uptake will be different based on tumor histopathology. 14 patients with primary renal tumors, clinically suspicious for RCC, underwent [99mTc]Tc-HYNIC-PSMA-11 SPECT/CT before surgery. All SPECT/CT images were reviewed separately. For quantitative analysis, volume of interest (VOI) was drawn over the tumor as well as the liver and maximum and mean counts were determined. In visual analysis, all renal lesions showed decreased uptake compared to the adjacent parenchymal tissue and liver. Whole body [99mTc]Tc-HYNIC-PSMA-11 scan in all cases could detect the region of tumoral lesion and the size and limits of the tumor were compatible with CT findings and histopathologic results. The ratio of maximum count of the tumor to the mean count of the liver showed no statistically significant difference between different subtypes (P value =0.50); however, the mean value was higher in clear renal cell RCC compared to non-clear cell RCC type (1.40 vs 1.23). In our study, the low and inconsistent uptake of [99mTc]Tc-HYNIC-PSMA-11 in primary tumor of RCC suggest that this radiopharmaceutical is not an ideal agent for imaging this patient population.