BACKGROUND: The aim of this study was to observe and characterize the nonspecific ¹⁸F-choline lymph node uptake in patients with prostate cancer.

MATERIAL AND METHODS: In this single center, prospective observational study which was done in University Hospital Center Zagreb between December 2012 and October 2014, 69 patients (median age 71 years; range 50–92) with prostate cancer were included. Patients underwent ¹⁸F-choline PET/CT for staging or restaging of prostate cancer. The mean follow-up period was 11.5 months. Kruskal-Wallis test was used to find out if the differences between SUV values of specific and nonspecific accumulation of the tracer are statistically significant.

RESULTS: Nonspecific accumulation of ¹⁸F-choline in lymph nodes was found in 36 patients (52.7%). Most of these findings (n = 24) were nonspecific accumulation of the tracer in mediastinal lymph nodes. Other sites of nonspecific tracer uptake were pulmonary hila (n = 20), inguinal lymph nodes (n = 15), and axillary lymph nodes (n = 10). Mean SUV values for mediastinal lymph nodes, pulmonary hila, axillary and inguinal lymph nodes were 4.8, 4.3, 3.1 and 4.1, respectively. Mean SUV value of nonspecific sites of tracer accumulation was lower (not significantly; (p = 0.2) than tracer uptake values measured in metastases sites (bone metastases mean SUVmax value — 13.2, metastatic lymph nodes mean SUVmax value — 9.2).

CONCLUSIONS: ¹⁸F-choline PET/CT is a valuable and an established functional diagnostic imaging method for staging and restaging prostate cancer. However, nonspecific uptake of the tracer can often be seen in lymph nodes not related to primary disease. Patient history, clinical examination, laboratory tests and correlation with other imaging methods, must be taken into consideration when interpreting ¹⁸F-choline PET/CT findings.