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

A renewed interest has been recently developed for the highly sensitive bone-seeking radiopharmaceutical F-NaF. Aim of the present study is to evaluate the potential utility of quantitative analysis of F-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 F-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 F-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 for MM lesions was 11.9 and mean SUV was 23.2. Respectively, SUV and SUV for degenerative lesions were 13.5 and 20.2. Kinetic analysis of F-NaF revealed the following mean values for MM lesions: K = 0.248 (1/min), k = 0.359 (1/min), influx (K) = 0.107 (1/min), FD = 1.382, while the respective values for degenerative lesions were: K = 0.169 (1/min), k = 0.422 (1/min), influx (K) = 0.095 (1/min), FD = 1. 411. No statistically significant differences between MM and benign degenerative disease regarding SUV, SUV, K, k and influx (K) were demonstrated. FD was significantly higher in degenerative than in malignant lesions. The present findings show that quantitative analysis of F-NaF PET data cannot differentiate malignant from benign degenerative lesions in MM patients, supporting previously published results, which reflect the limited role of F-NaF PET/CT in the diagnostic workup of MM.