Denosumab for Giant Cell Tumour of Bone

BoneNeoadjuvant

Denosumab for Giant Cell Tumour of Bone

Giant cell tumour of bone

Overview

  • Denosumab is a fully human monoclonal antibody targeting RANKL (receptor activator of nuclear factor kappa-B ligand)
  • RANKL is expressed by the neoplastic stromal cells of GCT and drives osteoclast-mediated bone destruction
  • Denosumab blocks RANKL, inhibiting osteoclast recruitment, resulting in tumour consolidation and new bone formation
  • Approved indications: unresectable GCT; pre-operative downstaging to allow limb salvage; recurrent/metastatic GCT; skeletally immature patients
  • Brand name: Xgeva (120 mg subcutaneous)

Regimen & Dosing

Regimen

  • Denosumab 120 mg subcutaneous injection
  • Loading doses: Day 1, Day 8, Day 15 of Cycle 1
  • Maintenance: 120 mg SC every 4 weeks (28-day cycles)
  • Duration: until disease progression, unacceptable toxicity, or surgical resection
  • Pre-operative use: typically 3–6 months prior to planned surgery

Dosing

  • Denosumab 120 mg SC on Days 1, 8, and 15 of Cycle 1 (loading phase)
  • Denosumab 120 mg SC on Day 1 of each subsequent 28-day cycle (maintenance)
  • No dose reduction schedule - consider dose delay for toxicity
  • Calcium and vitamin D supplementation mandatory: calcium ≥500 mg/day + vitamin D ≥400 IU/day unless hypercalcaemia present

Eligibility & Contraindications

Eligibility

  • Histologically confirmed giant cell tumour of bone
  • Unresectable disease (spine, pelvis, sacrum, skull base)
  • Resectable disease where denosumab may reduce surgical morbidity (downstaging)
  • Recurrent or metastatic GCT
  • Skeletally immature patients where surgery would damage physis
  • No prior severe hypersensitivity to denosumab

Contraindications

  • Hypocalcaemia - correct before initiating (risk of severe symptomatic hypocalcaemia)
  • Pregnancy and breastfeeding (teratogenic - effective contraception required)
  • Severe renal impairment (eGFR <30 mL/min) - increased risk of hypocalcaemia; use with caution
  • Active dental/jaw infection or planned invasive dental procedure - risk of osteonecrosis of the jaw (ONJ)
  • Prior history of ONJ

Monitoring

  • Baseline: serum calcium, phosphate, magnesium, creatinine, FBC, dental review
  • Calcium and vitamin D supplementation throughout treatment
  • Serum calcium at each cycle (Day 1): withhold if symptomatic hypocalcaemia
  • Dental review before initiation; avoid invasive dental procedures during treatment
  • Bone turnover markers (ALP, CTX) - optional, may reflect response
  • MRI of primary site every 3–6 months to assess response
  • Monitor for osteonecrosis of the jaw (ONJ): jaw pain, swelling, exposed bone
  • Rebound hypercalcaemia after cessation - monitor calcium for 8–10 weeks after stopping
  • FDG-PET or bone scan at clinician's discretion for disease assessment

Notes

  • Denosumab does NOT cure GCT - surgery remains the definitive treatment in most resectable cases
  • Rebound phenomenon after cessation: rapid tumour re-growth and hypercalcaemia reported - plan surgery before discontinuation
  • Pathological changes induced by denosumab (ossification) can make histological grading difficult - inform pathologist
  • Pulmonary 'metastases' (benign implants) in GCT may respond to denosumab - monitor with CT chest
  • Malignant GCT: denosumab has limited activity - treat as high-grade sarcoma
  • ONJ risk: ~1–2%; dental hygiene and avoidance of invasive procedures reduces risk
  • Do not abruptly discontinue without surgical plan - rebound tumour activity well documented
  • Off-label use for aneurysmal bone cyst showing emerging evidence