Evaluating Focal Areas of Signal Intensity (FASI) in Children with Neurofibromatosis Type-1 (NF1) Treated with Selumetinib on Pediatric Brain Tumor Consortium (PBTC)-029B.

Background: Understanding the effect of selumetinib on FASI may help elucidate the biology, proliferative potential, and role in neurocognitive changes for these NF1-associated lesions.

Methods: Patients with NF1-associated LGG and FASI treated with selumetinib on PBTC-029B were age-matched to untreated patients with NF1-associated FASI at Cincinnati Children's Hospital Medical Center. Paired bidirectional measurements were compared over time using nonparametric tests.

Results: Sixteen age-matched pairs were assessed (age range: 2.8-16.9 years, 60% male). Initial FASI burden was not different between groups (median range 138.7 cm [88.4-182.0] for the treated subjects vs. 121.6 cm [79.6-181.9] for the untreated subjects; = 0.98). Over a mean follow-up of 18.9 (±5.9) months, the LGG size consistently decreased with treatment while no consistent change among the treated or untreated FASI size was seen. At the paired time points, the median treated LGG decreased significantly more than the treated FASI (-41.3% (LGG) versus -10.7% (FASI), = 0.006). However, there was no difference in the median size change in the treated versus untreated FASI (-10.7% (treated FASI) versus -17.9% (untreated FASI), = 0.08). Among the treated subjects, there was no correlation between the change in LGG and FASI (r = -0.04, = 0.88).

Conclusions: Treatment with selumetinib did not affect the overall FASI size in children with NF1 treated for progressive low-grade glioma.