Assessment of surgical downstaging in an open-label Phase 2 trial of denosumab in patients with Giant Cell Tumour of Bone — ASN Events
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Assessment of surgical downstaging in an open-label Phase 2 trial of denosumab in patients with Giant Cell Tumour of Bone (#411)

Paul D Stalley 1 , Stefano Ferrari 2 , Piotr Rutkowski 3 , Robert J Grimer 4 , Sander PD Dijkstra 5 , Andrzej Pienkowski 3 , Gualter Vaz 6 , Leanne L Seeger 7 , Amy Feng 8 , Bruce A Bach 8
  1. Department of Orthopaedic Surgery, Royal Prince Alfred Hospital, Sydney, NSW, Australia
  2. Chemotherapy Unit, Istituto Ortopedico Rizzoli, Bologna, Italy
  3. Department of Soft Tissue/Bone Sarcoma and Melanoma, Maria Sklodowska-Curie Memorial Center and Institute of Oncology, Warsaw, Poland
  4. Orthopaedic Oncology Unit, Royal Orthopaedic Hospital, Birmingham, UK
  5. Department of Orthopedic Surgery, Leiden University Medical Center, Leiden, The Netherlands
  6. Department of Orthopedic Surgery, Edouard Herriot Hospital, Lyon, France
  7. Department of Radiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, USA
  8. Amgen Inc, Thousand Oaks, California, USA

Aims: Surgical resection, the standard treatment for giant cell tumour of bone (GCTB), may be associated with severe morbidity and may not be curative for all lesions. In an open-label phase 2 study, treatment with denosumab was associated with delayed surgery and/or a less morbid procedure in most patients with resectable GCTB. We report an unplanned, interim analysis of surgical downstaging in patients with resectable GCTB whose initially planned surgery was associated with severe morbidity.
Methods: Adults or skeletally mature adolescents with resectable GCTB received denosumab 120 mg SC every 4 weeks and on study days 8 and 15. Planned and actual GCTB surgical procedures following treatment are reported. Procedure selection and timing were based on review of radiographic imaging and clinical response.
Results: Overall, 222 patients enrolled and were evaluable for surgical downstaging (men, 46%; median age, 34 years); most had lesions in the lower (n=117) and upper (n=62) extremities or pelvis/sacrum (n=33). In total, 193 (86%) patients either had no surgery (n=109; 48%) or had a less morbid procedure (n=84; 37%). All 222 patients received denosumab; median (range) time on denosumab was 14.1 (1.0−57.1) months for all patients and 17.5 (1.0−57.1) months for the 109 patients with no surgery. The proportions of patients with a planned surgical procedure who had not undergone surgery were: hemipelvectomy (n=8/10; 80%), amputation (n=32/40; 80%), joint/prosthesis replacement (n=6/25; 24%), joint resection/fusion (n=14/35; 56%), en bloc resection (n=31/85; 36%), en bloc excision (n=7/8; 88%), curettage (n=8/18; 44%). The native joint preservation rate was 96% in the 25 patients with a planned joint/prosthesis replacement and 86% in 35 patients with a planned joint resection/fusion.
Conclusions: Consistent with initial results, treatment with denosumab was associated with delayed invasive surgery or a less morbid procedure than was planned in most patients with resectable GCTB.

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