Imaging of metastatic clear cell renal cell carcinoma with PSMA-targeted ¹⁸F-DCFPyL PET/CT.

OBJECTIVE

Molecular imaging with positron emission tomography (PET) provides a powerful means of identifying and characterizing cancerous processes, as well as providing a quantitative framework within which response to therapy can be ascertained. Unfortunately, the most commonly used PET radiotracer, ¹⁸F-fluorodeoxyglucose (FDG), has not demonstrated a definitive role in determining response to therapy in metastatic renal cell carcinoma (RCC). As a result, new radiotracers able to reliably image RCC could be of tremendous value for this purpose.

METHODS

Five patients with known metastatic RCC were imaged with the low-molecular weight radiotracer ¹⁸F-DCFPyL, an inhibitor of the prostate-specific membrane antigen at 60 min post injection. ¹⁸F-DCFPyL PET/CT and conventional images (either contrast-enhanced computed tomography or magnetic resonance imaging) were centrally reviewed for suspected sites of disease.

RESULTS

In all five patients imaged, sites of putative metastatic disease were readily identifiable by abnormal ¹⁸F-DCFPyL uptake, with overall more lesions detected than on conventional imaging. These PET-detected sites included lymph nodes, pancreatic parenchymal lesions, lung parenchymal lesions, a brain parenchymal lesion, and other soft tissue sites. ¹⁸F-DCFPyL uptake ranged from subtle to intense with maximum standardized uptake values (SUVmax) for the identified lesions of 1.6-19.3. Based upon this small patient series, limited pathology and imaging follow-up of these patients suggests a higher sensitivity for ¹⁸F-DCFPyL compared to conventional imaging in the detection of metastatic RCC (94.7 versus 78.9%).

CONCLUSIONS

PSMA expression in the tumor neovasculature of RCC has been previously established and is believed to provide the basis for the imaging findings presented here. PSMA-based PET/CT with radiotracers such as ¹⁸F-DCFPyL may allow more accurate staging of patients with RCC and conceivably the ability to predict and follow therapy in patients treated with agents targeting the neovasculature.