Inclusion Criteria:

1. Written and voluntary consent obtained from the patient or their legal guardians
2. Patient must be greater than 2 and less than 26 years old at time of study entry or at time of initial diagnosis
3. Patient must have had histologic verification of a solid malignancy at initial diagnosis (excluding brain stem tumors and visual pathway gliomas)
4. Patient must have recurrent measurable or evaluable disease after therapy or refractory to conventional therapy with presence of disease confirmed by standard imaging or biopsy
5. Must start protocol therapy within two weeks of disease evaluation and determination of eligibility
6. Performance status of > 20% on Lansky play scale for subjects < 10 years of age, > 20% on Karnofsky score for subjects >= 10 years of age
7. Patient must have fully recovered from acute toxic effects of prior therapy, to meet eligibility criteria
8. Adequate bone marrow function defined as peripheral absolute neutrophil count (ANC) > 500/mm^3, hemoglobin > 8 g/dl, platelets > 50,000/mm^3
9. Adequate renal function defined as serum creatinine < 1.5 X upper limit of normal (ULN) or age adjusted creatinine clearance of > 70 ml/min/1.73m^2
10. Adequate liver function defined as total bilirubin < 1.5 X upper limit of normal (ULN) and AST < 2 X upper limit of normal (ULN)
11. Serum calcium, phosphorus, or PTH levels must be </= to the upper limit of normal age adjusted values
12. Urine calcium level must be </= to the upper limit of normal value
13. Women of childbearing potential must have a negative serum or urine pregnancy test and not be breastfeeding prior to study therapy. Women of childbearing potential must be using an adequate form of contraception to avoid pregnancy during therapy and for at least 4 weeks after the end of study therapy in such a manner that the risk of pregnancy is minimized (Women of childbearing potential defined as not post-menopausal for 12 months or no previous surgical sterilization)

Exclusion Criteria:

1. Any past history of urine calcium stones, idiopathic hypercalcemia, hereditary bone disease, or hypercalciuria in the subject
2. Concurrent Medications: Patients currently taking digitalis or thiazides are ineligible
3. Concurrent Medications: Oral calcium and vitamin D supplements and all homeopathic medications must be discontinued 2 weeks prior to study entry and while on study therapy
4. Use of other anti-tumor therapy, including but not limited to chemotherapy, radiation therapy, immunotherapy, other investigational agents or other biologic therapy, during study therapy, with the exception of palliative radiation therapy to non-index lesions