Updated results from ALTER-S002: A single-arm multicenter trial of the combination of anlotinib with chemotherapy in patients with stage IIB classic osteosarcoma of the extremity.

11529 Background: The overexpression of multiple tyrosine kinase receptors in osteosarcoma indicated a promising therapy targeting these receptors. Anlotinib is a multi-targeted tyrosine kinase inhibitor that potentially inhibits tumor angiogenesis. The combination of anti-angiogenic drugs with chemotherapeutic agents is proposed to act synergistically to achieve favorable tumor control, especially as the neoadjuvant therapy. We had reported the neoadjuvant therapy data of anlotinib in combination with chemotherapy for treatment-naive stage IIB classical osteosarcoma of the extremity in the 2023 ESMO congress. Here we report an update on the effectiveness and safety of the follow-up. Methods: In this open-label, single-arm, multicenter phase II clinical trial. Eligible patients(pts) were aged 12-40 years with histologically confirmed primary localized extremity classic osteosarcoma, stage IIB, operable. Pts received anlotinib (10mg, po, d1-14, q3w), doxorubicin (A) (20-25mg/m 2 iv, d1-3, q3w) and cisplatin (P) (70-90mg/m 2 , iv, d1, q3w) for the first nine weeks. Pts underwent radical surgery after the exclusion of contraindications at week 10. After surgery, pts received A+P at weeks 12-14, and anlotinib plus A+P at weeks 15-20 with the drug dose unchanged. Since week 21, anlotinib (12mg, po, d1-14, q3w) monotherapy was maintained until week 104 or the occurrence of an EFS event. The primary endpoint was 24-month EFS rate, secondary endpoints were 36-month EFS rate, local recurrence rate, lung metastasis rate, 3-year OS rate and safety. Results: From May 2020 to Apr 2022, 52 eligible pts were enrolled, while 51 pts underwent surgery after 3 cycles of neoadjuvant therapy. At the data cut-off date (Oct. 2023), the median EFS was not reached, 12 and 24-month EFS rates were 84.18% (95% CI :70.82, 91.77) and 73.43% (95% CI :57.40, 84.21), respectively. The stratified analysis of EFS showed that the length and diameter of the target lesion are independent prognostic factors. The median OS was not reached, the 24-month OS rate was 95.92% (95% CI :84.65, 98.96). Among the 51 pts who underwent surgical treatment, 12(23.53%, 95% CI: 12.79, 37.49) pts experienced recurrence or metastasis. Most treatment-related adverse events (TRAEs) were grade 1-2. Grade 3/4 TRAEs (≥20%) included neutropenia (51.92%), leukopenia (38.46%), thrombocytopenia (36.54%) and anemia (32.69%). Conclusions: The updated results suggested that anlotinib combined with doxorubicin and cisplatin in the perioperative period showed favorable efficiency and manageable adverse events in Stage IIB classic osteosarcoma of the extremity. Clinical trial information: ChiCTR 2000033298.