Real‐world experience of tyrosine kinase inhibitors in children, adolescents and adults with relapsed or refractory bone tumours: A Canadian Sarcoma Research and Clinical Collaboration (CanSaRCC) study

OBJECTIVES: We conducted a retrospective multi‐centre study to assess the real‐world outcome of regorafenib (REGO) and cabozantinib (CABO) in recurrent/refractory bone tumours (BTs) including osteosarcoma (OST), Ewing sarcoma (EWS) and chondrosarcoma (CS)/extra‐skeletal mesenchymal CS (ESMC). METHODS: After regulatory approval, data from patients with recurrent BT (11 institutions) were extracted from CanSaRCC (Canadian Sarcoma Research and Clinical Collaboration) database. Patient characteristics, treatment and outcomes were collected. Progression‐free survival (PFS) and overall survival (OS) were estimated using the Kaplan–Meier method. RESULTS: From July 2018 to May 2022, 66 patients received REGO or CABO; 39 OST, 18 EWS, 4 CS and 5 ESMC. Median age was 27.8 years (range 12–76); median starting dose was 60 mg for CABO (n = 37, range 40–60) and 120 mg for REGO (n = 29, range 40–160). Twenty‐eight (42.4%) patients required dose reduction: hand‐foot syndrome 7 (10.6%), nausea/vomiting 1 (1.5%), diarrhoea 1 (1.5%), 2 elevated LFTs (3%), elevated bilirubin 1 (1.5%) and mucositis 1 (1.5%). The median OS for patients with OST, EWS, CS and ESMC was 8.5 months (n = 39, 95% CI 7–13.1); 13.4 months (n = 18, 95% CI 3.4–27.2), 8.1 (n = 4, 95% CI 4.1–9.3) and 18.2 (n = 5, 95% CI (10.4–na), respectively. Median PFS for OST, EWS, CS and ECMS was 3.5 (n = 39, 95% CI 2.8–5), 3.9 (n = 18, 95% CI 2.1–5.9), 5.53 (n = 4. 95% CI 2.13–NA) and 11.4 (n = 5, 95% CI 1.83–14.7), respectively. Age, line of therapy, REGO versus CABO, or time from diagnosis to initiation of TKI were not associated with PFS on univariable analysis. CONCLUSION: Our real‐world data show that TKIs have meaningful activity in recurrent BT with acceptable toxicities when started at modified dosing. Inclusion of TKIs in earlier lines of treatment and/or maintenance therapy could be questions for future research.