Delayed 18F-FDG PET for detection of paraaortic lymph node metastases in cervical cancer patients

This prospective study investigated the usefulness of dual-phase F-18-FDG PET scans (40 min and 3 h) in detecting paraaortic lymph node (PALN) metastasis for cervical cancer. Methods: One hundred four consecutive cervical cancer patients (international Federation of Gynecology and Obstetrics staging Ib-IVb, recurrent or persistent tumors) were included. All patients received a whole-body F-18-FDG PET scan at 40 min and an additional scan from the T11 level to the inguinal region at 3 h after injection of 370 MBq F-18-FDG. The maximum standardized uptake value (SUV) and retention index (RI [%], obtained by subtracting the normalized SUV value obtained at 40 min from that at 3 h) of the lesions were determined. Results: In all, 38 of the 104 patients were confirmed to have PALN metastases. For 31 patients (81.6%) with 13 upper (L1-L2 level) and 30 lower (L3-L4 level) PALNs, these metastases were detected with the 40-min scan. In addition, for 7 patients (18.4%) with 7 lower PALNs, metastases were found with the 3-h scan (RI = 12.6%). Two patients (3.0%) had 2 false-positive lesions initially (40 min) but were classified as benign with the 3-h scan. The sensitivity, specificity, and accuracy of 18F-FDG PET scans at 40 min were 81.6%, 97.0%, and 91.3%, respectively. These quantities were all 100% when both the 40-min and 3-h scans were taken together. Eight patients (21.1 %) had their treatment planning changed. We divided the 38 patients into 2 subgroups. Subgroup A included those with either only upper or only lower PALN metastases, and subgroup B included those with both upper and lower PALN metastases. In subgroup A, the SUV values were greater in the upper than in the lower PALNs in both the 40-min and 3-h images (P = 0.077). In subgroup B, there was no significant difference of SUV values between upper and lower PALNs in the 40-min (P = 0.433) and 3-h (P = 0.937) images. Conclusion: Our results showed that an additional 3-h scan is helpful for PALN detection of cervical cancer patients. A delayed image (3 h) is especially useful for lower PALN metastases.