Comparison of trans-1-amino-3-[¹⁸ F]fluorocyclobutanecarboxylic acid (anti-[¹⁸ F]FACBC) accumulation in lymph node prostate cancer metastasis and lymphadenitis in rats

Introduction: Trans-1-amino-3-[¹⁸ F]fluorocyclobutanecarboxylic acid (anti-[¹⁸ F]FACBC) is a positron emission tomography (PET) tracer used to visualize prostate cancer (PCa). In this study, we investigated the differences in anti-[¹⁸ F]FACBC accumulation between metastatic and inflamed lymph node (LN) lesions. Methods: A PCa LN metastasis (PLM) model was developed by inoculating a rat PCa cell line, MAT-Ly-Lu-B2, into popliteal LNs of Copenhagen rats. Acute lymphadenitis (AL) was induced by injecting concanavalin A (Con A) into the hind footpad, and chronic lymphadenitis (CL) was induced by daily injection of Con A into the tissues surrounding the popliteal LNs for 2 weeks. Main lesions of all animal models were established in lumbar and/or inguinal LNs. Biodistribution and dynamic PET imaging data were acquired after tracer injection. T2-weighted magnetic resonance (MR) images were registered with PET images. Results: In the biodistribution study, the uptake ratios of PLM-to-lymphadenitis in lesional lumbar and inguinal LNs were 0.97 − 1.57 and 1.47 − 2.08 at 15 and 60 min post-anti-[¹⁸ F]FACBC injection respectively. In PET imaging, the lesional lumbar LNs of CL and PLM, but not of AL, were visualized on anti-[¹⁸ F]FACBC-PET/MR fusion images without disturbance from radioactivity from urine, and the rank order of anti-[¹⁸ F]FACBC accumulation at 50 − 60 post-injection in lesional lumbar LNs was PLM > CL > AL. Conclusions: Anti-[¹⁸ F]FACBC accumulation in LNs with PLM was higher than that in inflamed LNs. Advances in knowledge: The study showed that although low but significant levels of anti-[¹⁸ F]FACBC uptake by chronic inflamed lesions might cause false-positives in anti-[¹⁸ F]FACBC-PET in some PCa patients, uptake of the tracer at acutely inflamed sites was minimal. Implications for patient care: The findings of this study suggest the potential of Anti-[¹⁸ F]FACBC for distinguishing between tumors and acute inflammation in clinical practice