What is the management and workup for a patient with a moth-eaten appearance of the proximal femoral metaphysis on X-ray (Xr) of the right femur?

Management and Workup of Moth-Eaten Proximal Femoral Metaphysis

A moth-eaten appearance in the proximal femoral metaphysis is highly concerning for malignant bone pathology—most commonly metastatic disease, multiple myeloma, or primary bone sarcoma—and requires urgent tissue diagnosis via biopsy alongside comprehensive staging workup. 1

Immediate Diagnostic Workup

Advanced Imaging

MRI of the entire femur with and without contrast is the critical next step to define the intraosseous and extraosseous extent of the lesion, assess cortical involvement, and evaluate fracture risk. 1 MRI demonstrates marrow signal abnormality and soft tissue extension that plain radiographs cannot detect. 1

• CT chest, abdomen, and pelvis with contrast is mandatory to identify a primary malignancy (lung, breast, kidney, thyroid, prostate are most common sources of bone metastases) and assess for systemic disease. 1
• Whole-body bone scintigraphy or PET-CT should be obtained to identify additional skeletal lesions and determine if disease is solitary or multifocal. 1
• CT of the affected femur without contrast (bone algorithm reconstruction) provides detailed cortical assessment for surgical planning if MRI is contraindicated. 1

Laboratory Evaluation

• Complete blood count, comprehensive metabolic panel, calcium, alkaline phosphatase, and lactate dehydrogenase to assess for metabolic derangements and tumor burden. 1
• Serum protein electrophoresis (SPEP), urine protein electrophoresis (UPEP), and serum free light chains to evaluate for multiple myeloma. 1
• Prostate-specific antigen (PSA) in men and consideration of tumor markers (CEA, CA 19-9, CA 15-3) based on clinical suspicion. 1

Tissue Diagnosis

Image-guided core needle biopsy is essential to establish histologic diagnosis before initiating treatment. 1 The biopsy tract should be planned along the anticipated surgical incision if resection is considered, to avoid tumor seeding. 1

Fracture Risk Assessment and Prophylactic Intervention

The combination of imaging findings and lesion-related pain is predictive of pathologic fracture risk. 1

Indications for Prophylactic Surgical Stabilization

Prophylactic surgery is recommended when: 1

• Persistent or increasing pain despite radiation therapy completion
• Lytic lesion involving >50% of cortical circumference
• Proximal femur involvement with lesser trochanter fracture
• Diffuse involvement of the femoral shaft
• Weight-bearing pain suggesting impending fracture

Intramedullary nailing is the preferred surgical approach for metastatic disease of the proximal femur, providing immediate stability and pain relief in 80-85% of patients. 1 For lesions involving the femoral head and neck, total hip arthroplasty with endoprosthetic reconstruction may be required. 1

Postoperative radiotherapy (30 Gy in 10 fractions or 20 Gy in 5 fractions) should be administered 2-4 weeks after orthopedic stabilization to achieve local tumor control. 1

Systemic Therapy Considerations

Bone-modifying agents (denosumab or zoledronic acid) should be initiated to reduce the incidence of skeletal-related events in patients with metastatic carcinoma or multiple myeloma involving bone. 1 Denosumab demonstrates superior reduction in skeletal-related events compared to zoledronic acid, though it carries higher risk of hypocalcemia. 1 Zoledronic acid has increased risk of renal toxicity and acute phase reactions. 1

Monitor serum calcium and supplement with calcium and vitamin D to prevent hypocalcemia, particularly with denosumab. 1

Critical Differential Diagnosis Pitfalls

While metastatic disease is most likely, primary bone sarcomas (osteosarcoma, leiomyosarcoma) can present with identical moth-eaten radiographic appearance and must be excluded via biopsy. 2, 3 These require fundamentally different treatment (limb-salvage surgery with neoadjuvant chemotherapy) compared to metastatic disease. 2, 3

Do not assume metastatic disease without tissue confirmation, as misdiagnosis can lead to inappropriate palliative treatment when curative resection was indicated. 2, 3

Contraindications to Surgical Intervention

Surgery should be avoided when: 1

• Life expectancy <4 weeks
• Poor general medical condition precluding safe anesthesia
• Inadequate reduction or suboptimal implant positioning cannot be achieved

Multidisciplinary Coordination

Immediate referral to orthopedic oncology, medical oncology, and radiation oncology is required for coordinated treatment planning. 1 The optimal sequence of biopsy, surgical stabilization, radiation, and systemic therapy depends on fracture risk, tumor histology, and overall prognosis. 1