Localization of primary prostate cancer with dual-phase 18F-fluorocholine PET.

Abstract

This study compared 18F-fluorocholine uptake in malignant and benign areas of the prostate at 2 time points to determine the suitability of delayed or dual-phase 18F-fluorocholine PET for localizing malignancy in the prostate gland. Twenty-six men (15 newly diagnosed with prostate cancer, 2 with recurrent prostate cancer, 6 with no evidence of prostate cancer recurrence after treatment, and 3 with no history of prostate cancer) underwent dual-phase PET consisting of initial whole-body PET starting 7 min after injection of 3.3-4 MBq/kg of 18F-fluorocholine followed by 1-h delayed PET of the pelvis. Tracer uptake in the prostate on the initial and delayed images was measured on a sextant basis. Prostate biopsy or whole-prostate histologic examination after radical prostatectomy was used to classify a prostate sextant as a dominant malignant region or probable benign region. For each sextant, a retention index based on the measured maximum standardized uptake value (SUVmax) was calculated on the initial and delayed images. In 15 prostates with both benign and malignant sextants on histologic examination, a malignant-to-benign ratio of SUVmax was also calculated for each time point. A dominant malignant region was found in 17 subjects, and a probable benign region was found in 24 subjects. The mean SUVmax for dominant malignant regions increased significantly between initial and delayed scans, from 7.6 to 8.6 (mean retention index, +14%; 95% confidence interval, 6%-22%; P = 0.002). The mean SUVmax for probable benign regions decreased significantly between initial and delayed scans, from 4.8 to 3.9 (mean retention index, -17%; 95% confidence interval, -10% to -23%, P < 0.001). The mean malignant-to-benign ratio increased significantly, from 1.4 on the initial scan to 1.8 on the delayed scan (P = 0.003). The areas under the receiver operating characteristic curves for distinguishing dominant malignant regions from probable benign regions based on initial SUVmax, delayed SUVmax, and retention index were 0.81, 0.92, and 0.93, respectively. On dual-phase PET of the prostate, areas of malignancy consistently demonstrated stable or increasing 18F-fluorocholine uptake, whereas most areas containing benign tissue demonstrated decreasing uptake. Delayed or dual-phase imaging after injection of 18F-fluorocholine may improve the performance of 18F-fluorocholine PET for localizing malignant areas of the prostate.