What are the requirements for Dual-Energy X-ray Absorptiometry (DEXA) scans in survivors of Acute Lymphoblastic Leukemia (ALL) after treatment?

DEXA Scan Requirements for Acute Lymphoblastic Leukemia Survivors

ALL survivors should receive baseline DEXA scans after treatment completion and follow-up scans every 2 years, especially those treated with cranial/craniospinal radiotherapy, total body irradiation, or high-dose corticosteroids.

Risk Factors for Low Bone Mineral Density in ALL Survivors

ALL survivors face significant risk of reduced bone mineral density (BMD) and increased fracture risk due to both the disease itself and its treatments. Key risk factors include:

Treatment-Related Factors

• Cranial or craniospinal radiotherapy (high-quality evidence for very low BMD) 1
• Total body irradiation (high-quality evidence for low BMD) 1
• High cumulative doses of corticosteroids (moderate-quality evidence) 1
• Methotrexate exposure 1
• Hematopoietic stem cell transplantation 1

Patient-Related Factors

• Hypogonadism (moderate-quality evidence) 1
• Growth hormone deficiency (moderate-quality evidence) 1
• Low BMI or underweight (high-quality evidence) 1
• Male sex (moderate-quality evidence) 1
• White race (moderate-quality evidence) 1
• Older age at diagnosis (≥10 years) 2
• Low physical activity 1
• Current or prior smoking 1

DEXA Scan Recommendations

Initial Assessment

• Baseline DEXA scan should be performed after completion of ALL therapy 1, 3
• The scan should include lumbar spine and hip(s) measurements, which are rated as "usually appropriate" (rating 9/9) by the American College of Radiology 1

Follow-up Schedule

• Every 2 years for patients treated with:

  • Cranial/craniospinal radiotherapy
  • Total body irradiation
  • High-dose corticosteroids 1

• More frequent monitoring may be warranted for patients with:

  • Previous abnormal DEXA results (Z-score <-1)
  • History of fractures during or after treatment
  • Ongoing endocrine abnormalities 1

Interpretation of DEXA Results

BMD Z-scores should be interpreted according to International Society for Clinical Densitometry criteria:

• Normal BMD: Z-score >-1
• Low BMD: Z-score between -1 and -2
• Osteoporosis: Z-score <-2 plus clinically significant fracture history 3

Clinical Implications

Studies show that 30-40% of ALL survivors may develop osteopenia and 8-11% may develop osteoporosis 3, 2. The fracture rate in ALL patients can be up to 6 times higher than in healthy controls 4, with approximately 18.5% of patients developing fractures 2.

Monitoring Considerations

• Consistency is critical: Use the same DEXA machine and anatomical sites for follow-up studies when possible 5
• Patient positioning: Proper positioning is essential for accurate measurements, with the femur properly rotated so the lesser trochanter is not visible during hip studies 5
• Artifact awareness: Be alert to potential artifacts that may affect measurements, including osteoarthritis, hardware from previous surgeries, and improper positioning 5

Common Pitfalls to Avoid

1. Delayed screening: Failing to obtain baseline DEXA scans after treatment completion
2. Inadequate follow-up: Not maintaining regular monitoring, especially in high-risk patients
3. Misinterpretation: Using adult T-scores instead of age-appropriate Z-scores for children and young adults
4. Overlooking modifiable risk factors: Not addressing vitamin D deficiency, inadequate calcium intake, and physical inactivity

While some studies suggest that BMD may normalize over time in some ALL survivors treated without cranial radiation 6, 7, the significant risk of fractures and potential long-term bone health issues warrant consistent monitoring throughout the lifespan, particularly for those with additional risk factors.