Diagnostic accuracy of MR imaging of patients with leptomeningeal seeding from lung adenocarcinoma based on 2017 RANO proposal: added value of contrast-enhanced 2D axial T2 FLAIR.

ABSTRACT

PURPOSE: We purposed to compare diagnostic accuracy of contrast-enhanced (CE) 3D T1-weighted fast field echo (3D T1-WI), CE 2D spin echo T1-weighted image (2D T1-WI), and CE 2D T2 FLAIR on evaluation of leptomeningeal metastasis(LM) using detailed features suggested in RANO proposal in a homogeneous group with cytology-proven LM. METHODS: Thirty-five lung adenocarcinoma patients with CSF cytology-proven leptomeningeal metastasis were enrolled in this retrospective analysis, who were enrolled in the prospective study (NCT03257124). MR images including CE 3D T1-WI, CE 2D T1-WI, and CE 2D FLAIR were reviewed. Presence of leptomeningeal nodule, leptomeningeal enhancement, and cranial nerve enhancement was evaluated according to the RANO proposal. Diagnostic accuracy of each sequence was compared and added value of CE 2D FLAIR to CE 3D T1-WI was evaluated. RESULTS: Two patients had unmeasurable small nodules recognized on 3D T1-WI only. Leptomeningeal enhancement was positive in 60%, 60%, and 77.1%, cranial nerve enhancement was positive in 51.4%, 45.7%, and 68.6% of the patients on 3D T1-WI, 2D T1-WI, and 2D FLAIR, respectively. Overall sensitivity for detection of LM was 71.4%, 71.4%, and 82.9% on 3D T1-WI, 2D T1-WI, and 2D FLAIR. When adding 2D FLAIR to 3D T1-WI, overall sensitivity for detection of LM was 82.9%. CONCLUSION: 3D T1-WI is the best for identifying leptomeningeal nodules. The sensitivity of 2D FLAIR is the highest for both LNE and CNE. Since both sequences are complementary, it can be helpful to take both sequences. Checking each feature according to the RANO proposal, especially CNE, may help you not to miss LM.