Quantitative analysis of ¹⁸F-NaF dynamic PET/CT cannot differentiate malignant from benign lesions in multiple...

A renewed interest has been recently developed for the highly sensitive bone-seeking radiopharmaceutical ¹⁸F-NaF. Aim of the present study is to evaluate the potential utility of quantitative analysis of ¹⁸F-NaF dynamic PET/CT data in differentiating malignant from benign degenerative lesions in multiple myeloma (MM). 80 MM patients underwent whole-body PET/CT and dynamic PET/CT scanning of the pelvis with ¹⁸F-NaF. PET/CT data evaluation was based on visual (qualitative) assessment, semi-quantitative (SUV) calculations, and absolute quantitative estimations after application of a 2-tissue compartment model and a non-compartmental approach leading to the extraction of fractal dimension (FD). In total 263 MM lesions were demonstrated on ¹⁸F-NaF PET/CT. Semi-quantitative and quantitative evaluations were performed for 25 MM lesions as well as for 25 benign, degenerative and traumatic lesions. Mean SUV_average for MM lesions was 11.9 and mean SUV_max was 23.2. Respectively, SUV_average and SUV_max for degenerative lesions were 13.5 and 20.2. Kinetic analysis of ¹⁸F-NaF revealed the following mean values for MM lesions: K₁ = 0.248 (1/min), k₃ = 0.359 (1/min), influx (K_i) = 0.107 (1/min), FD = 1.382, while the respective values for degenerative lesions were: K₁ = 0.169 (1/min), k₃ = 0.422 (1/min), influx (K_i) = 0.095 (1/min), FD = 1. 411. No statistically significant differences between MM and benign degenerative disease regarding SUV_average, SUV_max, K₁, k₃ and influx (K_i) were demonstrated. FD was significantly higher in degenerative than in malignant lesions. The present findings show that quantitative analysis of ¹⁸F-NaF PET data cannot differentiate malignant from benign degenerative lesions in MM patients, supporting previously published results, which reflect the limited role of ¹⁸F-NaF PET/CT in the diagnostic workup of MM.