A 17-year-old patient complains of pain in the area of the left knee joint. Soft tissues of thigh in the affected region are infiltrated, joint function is limited. X-ray picture of the distal metaepiphysis of the left femur shows a destruction focus with periosteum detachment and Codman's triangle found at the defect border in the bone cortex. X-ray of chest reveals multiple small focal metastases. What treatment is indicated?