11 C-Choline Pharmacokinetics in Recurrent Prostate Cancer.

The aim of this study was to investigate the value of pharmacokinetic modeling for quantifying ¹¹ C-choline uptake in patients with recurrent prostate cancer. Methods: In total, 194 patients with clinically suspected recurrence of prostate cancer underwent ¹¹ C-choline dynamic PET over the pelvic region (0-8 min), followed by a 6-min static acquisition at about 25 min after injection. Regions of interest were drawn over sites of disease identified by a radiologist with experience in nuclear medicine. ¹¹ C-choline uptake and pharmacokinetics were evaluated by SUV, graphical analysis (Patlak plot; K _i ^P ), and 1- and 2-compartment pharmacokinetic models ( K ₁ , K ₁ / k ₂ , k ₃ , k ₄ , and the macro parameter K _i ^C ). Twenty-four local recurrences, 65 metastatic lymph nodes, 19 osseous metastases, and 60 inflammatory lymph nodes were included in the analysis, which was subsequently repeated for regions of interest placed over the gluteus maximus muscle and adipose tissue as a control. Results: SUV _mean and K _i ^P were 3.60 ± 2.16 and 0.28 ± 0.22 min ^-1 in lesions, compared with 2.11 ± 1.33 and 0.15 ± 0.10 min ^-1 in muscle and 0.26 ± 0.07 and 0.02 ± 0.01 min ^-1 in adipose tissue. According to the Akaike information criterion, the 2-compartment irreversible model was most appropriate in 85% of lesions and resulted in a K ₁ of 0.79 ± 0.98 min ^-1 (range, 0.11-7.17 min ^-1 ), a K ₁ / k ₂ of 2.92 ± 3.52 (range, 0.31-20.00), a k ₃ of 0.36 ± 0.30 min ^-1 (range, 0.00-1.00 min ^-1 ) and a K _i ^C of 0.28 ± 0.22 min ^-1 (range, 0.00-1.33 min ^-1 ). The Spearman ρ between SUV and K _i ^P , between SUV and K _i ^C , and between K _i ^P and K _i ^C was 0.94, 0.91, and 0.97, respectively, and that between SUV and K ₁ , between SUV and K ₁ / k ₂ , and between SUV and k ₃ was 0.70, 0.44, and 0.33, respectively. Malignant lymph nodes exhibited a higher SUV, K _i ^P , and K _i ^C than benign lymph nodes. Conclusion: Although ¹¹ C-choline pharmacokinetic modeling has potential to uncouple the contributions of different processes leading to intracellular entrapment of ¹¹ C-choline, the high correlation between SUV and both K _i ^P and K _i ^C supports the use of simpler SUV methods to evaluate changes in ¹¹ C-choline uptake and metabolism for treatment monitoring.
(© 2018 by the Society of Nuclear Medicine and Molecular Imaging.)