Detecting prostate cancer metastases - PET/CT and the sentinel node technique

Abstract: Prostate cancer is one of the most common malignancies. Its treatment is highly dependent on the presence or absence of metastases. The available invasive and non-invasive modalities for detecting metastases are imperfect. Positron-emission tomography fused with computed tomography (PET/CT) is a non-invasive method for detecting metastases that is presently evaluated for prostate cancer. Fluoride and choline are PET/CT tracers with different properties; fluoride detects bone metastases only, while choline may detect metastases in bone, lymph nodes, and other organs. Sentinel node (SN) detection is an invasive method that allows selective dissection of the lymph nodes most likely to contain metastases. The SN technique may increase the detection rate by identifying metastases also outside the template of a standard lymphadenectomy. The clinical implications of the combination of choline and fluoride PET/CT were prospectively evaluated in Study I. The findings of choline PET/CT were compared with extended pelvic lymph node dissection (ePLND) in Study II. The clinical implications of early choline PET/CT in patients with biochemical recurrence (BCR) after radical prostatectomy (RP) was evaluated in Study III. SN detection was prospectively evaluated and compared with ePLND in Study IV. The main results were: 1) A fifth of patients with high-risk prostate cancer and normal or inconclusive planar bone scan had extensive metastatic findings on the PET/CT exams, leading to change of management. The choline and fluoride scans did on their own indicate metastases in patients in which the other scan did not. 2) Choline PET/CT had a high specificity (0.98) but, depending on the cut-off value of tracer uptake, had a low sensitivity (0.21–0.46) for lymph node metastases. 3) Choline PET/CT indicated metastases in 28% of hormone-naïve patients with BCR after RP and prostate-specific antigen of less than 2 ng/mL. 4) SN detection performed at least equal to ePLND in determining lymph node stage, with sensitivity 0.96. Conclusions: Choline and fluoride PET/CT and SN detection may be valuable diagnostic modalities for detecting metastases of prostate cancer.