Operative performance of RAPNO DIPG imaging criteria-a study from the International DIPG/DMG Registry.

Background: The Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group for diffuse intrinsic pontine glioma (DIPG) recently published its recommendations. We aim to test the operative performance of the RAPNO DIPG criteria imaging component by retrospectively applying it to a patient sample from the International DIPG/DMG Registry (IDIPGR).

Methods: Longitudinal MRIs for 46 patients were independently reviewed by 2 pediatric neuro-radiologists. Utilizing RAPNO DIPG imaging criteria for the pontine lesions, response was categorized as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). The response category for each MRI was compared between 2 readers and classified as concordant if they agreed, minor discordant if one reported SD and the other reported PR or PD, and major discordant if one reported PR and the other reported PD.

Results: A total of 277 paired MRIs were analyzed, and 124 paired MRIs were evaluated for concordance. The response category was concordant between readers in 84 (68%) MRI comparisons. In 31 MRI comparisons (25%) the reads were minor discordant, and major discordant in 9 (7%). No CRs were reported. Minor discordant cases were within 10% of the boundary for PR or PD in 20 (65%) of these cases. The median difference between the 2 readers' measurements was 2 mm (range 0-29 mm).

Conclusion: This study demonstrated that RAPNO DIPG imaging criteria can be applied with concordance or minor discordance between readers in 93% of the cases. Discordant measurements were largely at the boundaries of response type.