¹¹C-Choline pharmacokinetics in recurrent prostate cancer

The aim of this study was to investigate the value of pharmacokinetic modeling for quantifying ¹¹C-choline uptake in patients with recurrent prostate cancer. Methods: In total, 194 patients with clinically suspected recurrence of prostate cancer underwent ¹¹C-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. ¹¹C-choline uptake and pharmacokinetics were evaluated by SUV, graphical analysis (Patlak plot; K_i ^P), and 1- and 2-compartment pharmacokinetic models (K₁, K₁/k₂, k₃, k₄, 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: SUVmean 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 K1 of 0.79 ± 0.98 min^-1 (range, 0.11-7.17 min^-1), a K₁/k₂ of 2.92 ± 3.52 (range, 0.31-20.00), a k₃ 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 γ 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 K₁, between SUV and K₁/k₂, and between SUV and k₃ 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 ¹¹C-choline pharmacokinetic modeling has potential to uncouple the contributions of different processes leading to intracellular entrapment of ¹¹C-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 ¹¹C-choline uptake and metabolism for treatment monitoring.