Results of a randomized prospective clinical trial evaluating maintenance chemotherapy in patients with high-grade, operable osteosarcoma: A report from the Latin American Group of Osteosarcoma Treatment.

10532 Background: Preclinical models show that a daily antiangiogenic regimen at low-dose may be effective against chemotherapy-resistant tumors. In patients (pts) with high grade, operable osteosarcoma (OST) of the extremities, efficacy of maintenance therapy with continuous oral cyclophosphamide and methotrexate was investigated. Methods: Pts ≤30yrs with high-grade OST were eligible for registration at diagnosis. Eligibility for randomization included: 1. Non-metastatic pts 2. high-grade extremity OST 3. receipt of two cycles pre-operative methotrexate, doxorubicin, cisplatin (MAP); 4. complete macroscopic resection of primary tumor. The study design includes a backbone of 10 weeks of preoperative therapy using MAP. Following surgery, non-metastatic pts were randomized by blocks to complete 31 weeks of MAP or to receive 73 weeks of maintenance therapy following MAP; while metastatic pts received maintenance therapy in combination with MAP since the beginning of treatment. The primary end point was event...