RAPNO Criteria and MRI Assessment in PLGG: Recommendations vs. Real-World Practice

In this segment, Dr. Chi, Dr. Chintagumpala, and Dr. Abdelbaki discuss the RAPNO (Response Assessment in Pediatric Neuro-Oncology) criteria and how radiographic assessment is applied, and sometimes misapplied, in pediatric low-grade glioma (PLGG).

RAPNO is not typically referenced by name in family discussions, according to Dr. Chi, who says "our child is our best assessment tool and certainly the MRIs, too, and all of the other symptomatology that, played into whether or not a therapy was warranted." Many PLGGs are non-contrast enhancing, making contrast uptake an unreliable marker; T2/FLAIR sequences may reveal more immediate changes. The transition from a non-enhancing to an enhancing tumor warrants attention, particularly when enhancement appears with ragged edges or necrotic features. These findings more concerning in older adolescents, although nodular enhancement can fluctuate and does not always signify progression. RAPNO criteria offer useful recommendations, particularly regarding cyst assessment and which MRI sequences to evaluate but require prospective validation and are not day-to-day rules. The clinical difference between a 23% and a 27% increase is negligible; outside of trials, these criteria serve as guidelines, not rigid rules.

Radiology reports sometimes describe increased contrast uptake as progression, which can alarm families unnecessarily. T2/FLAIR imaging is the more reliable sequence for PLGG assessment, as contrast uptake may fluctuate spontaneously over serial scans.

In the next episode, "Applying RAPNO Criteria with Clinical Judgment in PLGG," the panel examines the practical limitations of applying percentage-based RAPNO progression criteria outside of clinical trials.