This is a Phase 2, open-label, randomized, controlled clinical study of pediatric subjects treated with pamidronate with calcium and vitamin D versus calcium and vitamin D alone following hematopoetic cell transplantation (HCT). The purpose of this study is to test the hypothesis that subjects receiving pamidronate with calcium and vitamin D will have higher lumbar spine bone mineral content (LBMC; adjusted for height, age, sex, Tanner stage, and race) measured by dual-energy X-ray tomography (DXA) at 1 year post-HCT than subjects receiving calcium and vitamin D alone (Control Group). Sixty subjects (≥1 and <18 years of age at the time of enrollment and receiving an allogeneic HCT for a hematologic malignancy or severe aplastic anemia) will be evaluated at the University of Minnesota Amplatz Children's Hospital and Seattle Children's Hospital. Subjects randomized to pamidronate treatment will receive infusions approximately 100, 180, and 270 days after HCT. Laboratory evaluations, DXA, and peripheral quantitative computed tomography (pQCT) will be performed at specified time points to evaluate safety and treatment efficacy. Subjects will participate in the study for 1 year. In addition, the following secondary hypotheses will be tested:
- Subjects treated with pamidronate will have higher total body BMC (TBMC; excluding head; adjusted for height, age, sex, Tanner stage, and race) measured by DXA 1 year post-HCT compared to the Control Group.
- Subjects treated with pamidronate will have higher total bone mineral density (BMD), cortical BMD, trabecular BMD, and estimated bone strength measured by pQCT 1 year post-HCT compared to the Control Group.
- Cytokine levels will increase rapidly in the first 3 weeks after HCT, preceding an increase in markers of bone resorption.
- In the Control Group, increased cytokine levels and receptor activator of nuclear factor-κ B ligand (RANKL)/ osteoprogerin (OPG) ratio 3 weeks post-HCT will be associated with decreased BMC and BMD at 1 year post HCT.
- Markers of bone resorption will increase in the first 100 days after HCT, will remain elevated until at least Day 180 in the Control Group, but will decrease after initiation of pamidronate at Day 100 in the Pamidronate Group.
- Markers of bone formation, including osteocalcin (OCN) will decrease in the first 100 days after HCT and in the Control Group lower OCN levels at Day 100 will be associated with lower BMC and BMD 1 year post-HCT.