While the clinical need for and the scientific merit remain valid, this regulated drug trial was not feasible logistically due to limited funds.

This study explores the effect of zoledronic acid on incident vertebral fractures and osteonecrotic lesions in children recently diagnosed with acute lymphoblastic leukemia.

Inclusion Criteria:

1. Subject or subject's legally acceptable representative has provided informed consent.

2. Children aged 8 to 16 years at the time of enrolment with a confirmed diagnosis of acute lymphoblastic leukemia (ALL).

3. Children with vertebral fractures or osteonecrotic lesions according to the following criteria:

   1. children with vertebral fractures on lateral spine x-ray and/or osteonecrotic lesions on MRI of the hips and/or knees identified through routine clinical screening at least 8 weeks following chemotherapy initiation OR
   2. children with vertebral fractures on lateral spine x-ray and/or osteonecrotic lesions of the hips and/or knees on MRI that are identified at any time in the first 12 months after chemotherapy initiation following presentation with back pain (in the case of vertebral fractures, identified by lateral spine x-rays) and/or hip pain (in the case of osteonecrotic lesions, identified by MRI) and/or knee pain (in the case of osteonecrotic lesions, identified by MRI).

Exclusion Criteria:

1. Any child for whom the treating physician feels participation is not advised.
2. Prior treatment with an osteoporosis agent (e.g. bisphosphonate).
3. Co-morbidities affecting musculoskeletal health (e.g. cerebral palsy).
4. Children with renal failure (eGFR<60ml/min/1.73m2).
5. Children with untreated vitamin D deficiency (vitamin D <50nmol/L).
6. Children with hypocalcemia.
7. Children planning dental procedures and/or dental surgery during the course of the study.
8. Children with asthma who are acetylsalicylic acid (ASA) sensitive.
9. Children with a documented history of atrial fibrillation.
10. Currently pregnant or planning a pregnancy during the study.
11. Currently breastfeeding or planning on breastfeeding during the study.