Non-inferiority of a non-gadolinium-enhanced magnetic resonance imaging follow-up protocol for isolated optic pathway gliomas.

Background: Pediatric patients with optic pathway gliomas (OPGs) typically undergo a large number of follow-up MRI brain exams with gadolinium-based contrast media (GBCM), which have been associated with gadolinium tissue retention. Therefore, careful consideration of GBCM use in these children is warranted.

Objective: To investigate whether GBCM is necessary for OPG MR imaging response assessment using a blinded, non-inferiority, multi-reader study.

Materials And Methods: We identified children with OPG and either stable disease or change in tumor size on MRI using a regional cancer registry serving the U.S. Pacific Northwest. For each child, the two relevant, consecutive MRI studies were anonymized and standardized into two imaging sets excluding or including GBCM-enhanced images. Exam pairs were compiled from 42 children with isolated OPG (19 with neurofibromatosis type 1), from a population of 106 children with OPG. We included 28 exam pairs in which there was a change in size between exams. Seven pediatric radiologists measured tumor sizes during three blinded sessions, spaced by at least 1 week. The first measuring session excluded GBCM-enhanced sequences; the others did not. The primary endpoint was intra-reader agreement for ≥ 25% change in axial cross-product measurement, using a 12% non-inferiority threshold.

Results: Analysis demonstrated an overall 1.2% difference (95% confidence interval, -3.2% to 5.5%) for intra-reader agreement using a non-GBCM-enhanced protocol and background variability.

Conclusion: A non-GBCM-enhanced protocol was non-inferior to a GBCM-enhanced protocol for assessing change in size of isolated OPGs on follow-up MRI exams.