Locally Advanced Gctb Recurrence After Neoadjuvant Denosumab Use.

e23507 Background: Giant Cell Tumor of Bone is a RANK/RANK-ligand (RANKL) positive, aggressive, locally destructive tumor leading to pain and impairment of movement and limb function. Even though surgery remains the standard treatment, the use of denosumab, monoclonal antibody RANK-L inhibitor is associated with tumor response and surgical morbidity, with downstaging benefit. Methods: All GCTB patients from 2005 to 2020 from Pernambuco Cancer Center Hospital were included in the study and followed up. All patients received Denosumab 120mg on D1, D8 and D15 (attack phase), and maintenance phase of 120mg monthly. Results: A total of Fifty GCTB Patients were included in the study, being mostly women (62%), between 21-40 yrs. old (56%), Capanacci III (72%), with tumors located in femur (41%), tibia (23%), and more rarely in talus or orbit. Denosumab neoadjuvant was prescribed to 40 patients, being 28 locally advanced disease and 12 irresectable or metastatic disease, with a median of 10 doses received. Among resectable Patients, after neoadjuvant denosumab, 25 were submitted to intralesional surgery (curettage/bone cement) and 3 to en-bloc surgery/prothesis. Overall recurrence after neoadjuvant denosumab was observed in 22% (9/40) and 32% (8/25) among Patients that received neoadjuvant denosumab and intralesional surgery. Denosumab was approved for irresectable GCTB, or when surgery may render high morbidity. Neoadjuvant Denosumab use has been related to lower recurrence rate, as well as reduction in invasive procedures morbidity and sequelae in motricity. In the present study, recurrence rate of 22%, regardless of the therapeutic modality applied, corroborates recurrence rates in published data (16-30%). Among locally advanced patients, even though recurrence rates are expectedly higher, there were lower rates of aggressive surgery and joint preservation. Motor sequelae was observed in 12,5% (5/40) of patients, with quality of life improvement and pain reduction after treatment. Conclusions: Neoadjuvant denosumab for GCTB provides promising results, with acceptable recurrence rates, as well as a less aggressive approach, with lower risk of morbidity or sequelae and excellent safety profile.