Serum phosphorus calcium, magnesium and potassium >= lower limit of normal (LLN) 55.0 Serum calcium and magnesium above the institutional lower limit of normal, within 14 days of registration and within 7 days of the start of treatment 180.0 Serum phosphorus >= lower limit of normal (LLN) 42.0 Calcium >= LLN 42.0 Magnesium >= LLN 42.0 Potassium >= LLN 42.0 Serum phosphorus, calcium, magnesium and potassium >= lower limit of normal (LLN) 72.0 Serum phosphorus >= lower limit of normal (LLN) 90.0 Serum calcium >= LLN 90.0 Serum magnesium >= LLN 90.0 Serum potassium >= LLN 90.0 Serum phosphorus >= lower limit of normal (LLN) (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) 135.0 Serum calcium >= LLN (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) 135.0 Serum magnesium >= LLN (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) 135.0 Serum potassium >= LLN (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) 135.0 RECURRENT/ PROGRESSIVE DIPG (STRATUM 1): Potassium >= lower limit of normal (LLN) 50.0 RECURRENT/ PROGRESSIVE DIPG (STRATUM 1): Serum total calcium (correct for serum albumin) or ionized calcium >= LLN 50.0 NON-PROGRESSED DIPG (STRATUM 2): Serum total calcium (correct for serum albumin) or ionized calcium >= LLN 50.0