e23511 Background: Giant cell tumour of bone (GCTB) is a locally aggressive and osteolytic tumour.The peak incidence is during the third and fourth decades of life. The majority of tumours occur in the metaepiphyseal (end) region of the long bones. Surgical resection is the preferred treatment option, if possible but it is a tumor which always poses progressive problems. Denosumab is indicated in recurrent or unresectable GCTB. Methods: We report a series of 70 patients treated for GCT at the medical oncology department of the CPMC (Algiers) in collaboration with the orthopedics department of Mustapha University Hospital from January 2020 to December 2023. Results: 70 patients ( 50 women and 20 men). The sex ratio is 0.54 The average age is 22 years (11-54 years). Reason for consultation : - Pathological fracture: n = 10 - Pain: n = 30 - Functional impotence: n = 20 - Tumor mass: n = 5 - Concept of trauma: n = 5 Stage of the disease: -Localized: n = 29 -Recurrence: n = 30, -Recurrence + pulmonary metastases: n = 10, -Sarcomatous transformation: n = 1 Type of treatment: -Radiotherapy, n = 1 -Exercised biopsy: n = 10, -Curettage + cementoplasty: n = 50 -Exeresis with osteosynthesis material: n = 8, -Amputation : n = 1 Medical treatment: Denosumab: n = 45 The number of courses with denosumab was between 6 and 55 cycles. Denosumab was administered neoadjuvantly in 10 patients, in 20 patients with reccurence disease, 15 patients in the metastatic phase - In terms of toxicity, we noted moderate hypocalcemia in 3 patients. -Objective responses: 95% ORR, 5 complete radiological responses and 10 partial responses, 20 stable patients and 9 out of 10 patients who received neoadjuvant denosumab were able to operate.Progression Free Survival was 28 months. Conclusions: GCTs are aggressive tumors with intermediate malignancy that should not be underestimated. The treatment is essentially surgical. Denosumab is indicated for both neoadjuvant and adjuvant use, it allows obtaining a clear clinical and radiological improvement.