Retrocrural lymph node metastasis revealed by FDG PET/CT: A predictor of supra-diaphragmatic spread in ovarian cancer

Objectives Retrocrural lymph nodes (RCLNs) communicate with para-aortic LNs in upper abdomen and posterior mediastinal LNs. It is possible that, when RCLNs are involved, supra-diapharagmatic extension would occur in abdomino-pelvic cancers. However, there is no study to prove this assumption so far. We investigated whether RCLN metastases detected on FDG PET/CT can be a predictor of supra-diaphragmatic spread of ovarian cancer.

Methods In year 2007 and 2008, 510 patients with ovarian cancer underwent F-18 FDG PET/CT in our institute. Among them, 50 were revealed to be stage IV. Two nuclear medicine physicians assessed the metastases in RCLNs on FDG PET/CT images. We subdivided the population by mode of metastases, who had hematogenous metastases in extraperitoneal organs such as the liver, lung and bone (group 1), lymphatic metastases in supra-diaphragmatic LNs (group 2) and both organs and LNs (group 3). The incidences of RCLN metastasis between three subgroups were compared.

Results Among 50 patients with stage IV, 24 patients had RCLN metastases (48%). The number of patients was 12 in group 1, 25 in group 2, and 13 in group 3. FDG PET/CT showed RCLN metastasis in 2 patients of group 1 (16.7%), 16 patients of group 2 (64%), and 6 patients of group 3 (46.2%). By Chi-square test, group 2 and group 2 plus group 3 showed significantly higher incidence of RCLN metastasis than group 1 (p<0.05, p<0.05). In addition, RCLN metastasis was found on FDG PET/CT in 6 out of 17 patients (35.3%) having malignant pleural effusion.

Conclusions Interestingly, the incidence of RCLN metastasis was considerably high in patients with stage IV ovarian cancer (48%). The incidence was higher in patients who had supra-diaphragmatic LN metastases than in patients having hematogenous metastases. These findings suggest that RCLN metastasis revealed by FDG PET/CT could be used as a predictor of extraperitoneal spread of ovarian cancer, especially supra-diaphragmatic lymphatic metastasis