LGG-02. A PHASE II PROSPECTIVE TRIAL OF SELUMETINIB IN CHILDREN WITH RECURRENT/PROGRESSIVE PEDIATRIC LOW-GRADE GLIOMA (PLGG) WITH A FOCUS UPON OPTIC PATHWAY/HYPOTHALAMIC TUMORS AND VISUAL ACUITY OUTCOMES: A PEDIATRIC BRAIN TUMOR CONSORTIUM (PBTC) STUDY, PBTC-029B. (23rd April 2019)