Feasibility of integrated PET/MRI and PET/CT imaging for gynecological malignancies

Objectives: To assess the technical feasibility and diagnostic performance of FDG-PET/MRI whole body imaging compared to PET/CT for staging of patients with a gynecological malignancy. Methods: From February 1, 2014 to December 31, 2016, a total of 25 patients with a gynecologic malignancy were prospectively enrolled into this pilot study. Patients underwent sequential PET/CT and PET/MRI whole body imaging studies after administration of a single dose of F-18 FDG. PET/MRI and PET/CT images were independently reviewed by two expert radiologists. Readers were blinded to the results of the other imaging procedures. Clinical and pathologic information was abstracted from medical charts. Results: 18 patients were included in the final analysis, 7 were excluded - 3 due to inability to tolerate PET/MRI due to claustrophobia, 3 due to enrollment at time of recurrence, and 1 due to lack of surgical or clinical staging. Median age of patients was 62 years (range 31-88). 56% of patients were non-Hispanic white and median BMI was 27 kg/m2 (range 19-37). 61% of patients (11/18) had cervical cancer, while the remaining patients had endometrial cancer. PET/MRI as compared to PET/CT was able to detect 18/18 primary tumors, 7/7 patients with regional lymph nodes, and 1/1 patient with an abdominal metastasis. 2 patients had additional lymph nodes outside of the abdominopelvic cavity detected on PET/CT that were not seen on PET/MRI. Whereas, 6 patients had parametrial invasion and 1 patient had invasion of the bladder clearly seen on PET/MRI not detected on PET/CT. 5 cervical cancer patients had discordant clinical versus radiographic staging based on PET/MRI detection of soft tissue involvement not clinically palpated (see Table 1). Management changed for one patient who had clinical stage IB1 and radiographic stage IIB cervical cancer with treatment changing from surgery to chemoradiation. Conclusions: PET/MRI is feasible and has at least comparable diagnostic ability to PET/CT for identification of primary cervical and endometrial tumors and regional metastases. PET/MRI may be superior to PET/CT for initial radiographic assessment of cervical cancers and have added benefits in assessing treatment response for these cancers. Additional studies are needed to investigate which patients would benefit the most from PET/MRI. Learning objectives: Identify situations in which FDG-PET/MRI might be a useful adjunct to staging of gynecologic malignancies.