Serum phosphorus calcium, magnesium and potassium >= lower limit of normal (LLN) 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 Serum phosphorus >= lower limit of normal (LLN) Calcium >= LLN Magnesium >= LLN Potassium >= LLN Serum phosphorus, calcium, magnesium and potassium >= lower limit of normal (LLN) Serum phosphorus >= lower limit of normal (LLN) Serum calcium >= LLN Serum magnesium >= LLN Serum potassium >= LLN 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) Serum calcium >= LLN (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) Serum magnesium >= LLN (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) Serum potassium >= LLN (if below LLN, for asymptomatic patients replacement may be initiated if clinically indicated without delaying the start of study treatment) RECURRENT/ PROGRESSIVE DIPG (STRATUM 1): Potassium >= lower limit of normal (LLN) RECURRENT/ PROGRESSIVE DIPG (STRATUM 1): Serum total calcium (correct for serum albumin) or ionized calcium >= LLN NON-PROGRESSED DIPG (STRATUM 2): Serum total calcium (correct for serum albumin) or ionized calcium >= LLN