Comparison of Magnetic Resonance Imaging (MRI) and Positron Emission Tomography-Computed Tomography (PET CT) for Detection of Parametrial Involvement and Lymph Node Metastasis in Patients with Cervical Cancer: A Prospective Study

Abstract

There are few lacunae in the Federation Internationale de Gynecologie et d’Obstetrique (FIGO) staging system for Carcinoma of cervix, as the patients are not assessed for lymph node as well as distant metastases, though these are important prognostic factors. Magnetic resonance imaging (MRI) as well as Flurodeoxy glucose positron emission tomography/computed tomography (FDG PET/CT) has been used for evaluation of local tumor extent and nodal as well as distant metastasis in case of cervical cancer. To compare the usefulness of MRI and FDG PET/CT for detection of parametrial involvement and lymph node metastasis in increasing the accuracy of staging of patients with cervical cancer. In this prospective hospital-based study, 38 patients with cervical cancer were prospectively enrolled. Patients were studied in two groups; Group A (22 cases) included recently diagnosed cases for initial workup and base line staging (prior to any treatment). Group B (16 cases) included treated cases of cervical cancer, on follow-up, suspected clinically to have recurrence, at 6 months or more after completion of planned standard treatment. MRI and FDG PET/CT scan were performed within 1-week interval of each other for all enrolled patients. The criterion for lymph node metastases on MRI was size > 10 mm in short axis diameter and abnormal signal or contrast enhancement in parametrium for involvement. On FDG PET/CT, only areas with FDG uptake significantly higher than the background and FDG uptake visible on at least two consecutive axial slices were considered as positive for malignancy. MRI and FDG PET/CT findings were compared with histopathologic examination (HPE). Group A: On patient-based analysis, MRI versus FDG PET/CT sensitivity for detection of lymph node metastases was: 57 versus 86%, specificity was 71 versus 71% and diagnostic accuracy was 64 versus 78%, respectively. On lymph node-based analysis, MRI versus FDG PET/CT sensitivity was 50 versus 87%, specificity 98 versus 98 and diagnostic accuracy 97 versus 98%, respectively. The efficacy of MRI for detecting parametrial invasion was (sensitivity = 67%, specificity = 91%, diagnostic accuracy was 86%) and for FDG PET/CT was (sensitivity = 0%, specificity = 91%, diagnostic accuracy = 71%). The FIGO staging was found to be inaccurate in 21% cases. Group B: For local disease recurrence: MRI versus FDG PET/CT, the sensitivity was 83 versus 92%, specificity was 75 versus 75% and accuracy was 81 versus 87%. Sensitivity and accuracy of MRI was better than FDG PET/CT in detection of local disease recurrence. When MRI and FDG PET/CT were compared for detecting nodal recurrence, according to cases, the sensitivity was 83 versus 92%, specificity was 75 versus 75% and accuracy was 81 versus 87%. FDG PET/CT had higher sensitivity and accuracy than MRI in detection of lymph nodal recurrence. FDG PET/CT is superior to MRI in detection of local as well as distant lymph node metastases. FDG PET/CT has ability to detect distant metastases beyond the true pelvis. MRI is superior to PET/CT for detection of early parametrial invasion and local recurrence.