PD22-11: Accuracy of pelvic lymph nodal staging in Urothelial Carcinoma of Urinary Bladder by Multiparametric MRI and 18-FDG PET/CT: A Prospective comparative study
Introduction: Accurate lymph-node staging of patients with muscle-invasive bladder cancer (BC) is decisive for the allocation to optimal treatment algorithms. Contrast-enhanced CT imaging has been the guideline-recommended standard for years. However, sensitivity and specificity are limited with significant inter-rater variability. Metabolic imaging like FDG PET/CT has a low pooled sensitivity of 57% and pooled specificity of 92% in pre-operative detection of lymph nodes. Similarly sensitivity of MRI for nodal staging have been reported and sensitivity varies from 40-88% with concomitant specificities of 75-91%. . Current improvements in MRI technology due to addition of functional MR sequences i.e. dynamic contrast-enhanced (DCE) imaging and diffusion-weighted imaging (DWI) have enhanced its clinical utility. The current study was designed to compare the diagnostic efficacy of multiparametric MRI (mp-MRI) over FDG PET/CT to detect lymph node metastases. Methods: The current study was a prospective comparative analysis to evaluate the diagnostic performance of mpMRI over FDG PET/CT for nodal evaluation of bladder cancer patients. Total of 24 patients with biopsy proven muscle invasive bladder cancer were subjected to mpMRI and FDG PET/CT for evaluation of nodal status pre-operatively . For mpMRI ADC value cut off of 0.8 x 10-3 mm2/s was used to predict presence of lymph node metastasis. While SUVmax cutoff of 3.5 was used to predict significant lymphadenopathy in FDG PET CT. SUVmax cutoff of 3.5 was used to predict significant lymphadenopathy.Out of the 24 patients enrolled 17 underwent surgery and were included in the study. Accuracy of each imaging was determined with the gold standard histolopathological evaluation. Differences in sensitivity, specificity, and accuracy between MRI and PET/CT were estimated using the McNemar exact test. Results: The majority of patients were male (94%) and elderly (94%). Out of the 17 patients, 10 patients had positive nodes on the surgical specimen. Sensitivity of PET/CT and mpMRI for node detection were 70% and 80% respectively with specificity of 80% and 100%.PPV of mpMRI was 100% compared to 87.5% for PET CT. NPV was also high for mpMRI (77.8%) compared to PET CT (66.67%) with overall accuracy of 88.26% for mpMRI compared to 76.47% for PET Conclusions: The study indicated a better diagnostic performance for mpMRI compared to PET CT for nodal staging. However, this did not achieve statistical significance. mpMRI based assessment might improve standardization and have a great potential to significantly improve staging of BC patients in the future. SOURCE OF Funding: none
