Potential impact of 18F-FDG PET/CT on patients selection for neoadjuvant chemotherapy before radical cystectomy

Background The detection of lymph node metastases in bladder cancer has a major impact on treatment decisions and patients prognosis. Due to limited value of conventional imaging, the place of molecular and functional imaging needs to be precised, particularly in the neoadjuvant setting. Methods From June 2011 to June 2013, 102 patients with clinically localized BCa were simultaneously staged with 18F-FDG PET/CT before RC. This study assessed the diagnostic accuracy of 18F-FDG PET/CT for the detection of metastases in normal-sized lymph nodes using extended pelvic lymph node dissection and histopathology as the reference standard. Results A total of 1211 LNs were examined histopathologically. Sixty-seven (5.5%) metastatic nodes were found in 26/102 patients (25.5%). Lymph node density was 22%. On patient-based analysis, sensitivity, specificity, predictive positive value (PPV), negative positive value (NPV) and accuracy for 18F-FDG PET/CT were calculated as 50%, 96.2%, 80%, 86.2% and 85.3% respectively. On a field-based analysis, sensitivity, specificity, PPV, NPV and accuracy for 18F-FDG PET/CT were calculated as 50.0%, 99.0%, 71.9%, 97.4%, and 96.5% respectively. The majority of missed metastases were micrometastasis <5 mm in long axis diameter. Conclusions 18F-FDG PET/CT improves diagnostic efficacy for lymph node staging in patients staged N0 with conventional cross-sectional imaging. 18F-FDG PET/CT could be used as a surrogate marker for detection of metastases in non-enlarged pelvic lymph nodes and enhances management strategy guiding patients selection for neoadjuvant chemotherapy.