Skip metastases in osteosarcoma: experience of the Cooperative Osteosarcoma Study Group

Purpose The outlook for patients with osteosarcoma who present with synchronous regional bone metastases (skip metastases), either in the primary bone site or transarticular, is considered to be extremely poor. This study was conducted to further investigate the prognostic implication of skip metastases in osteosarcoma. Patients and Methods The authors retrospectively analyzed the collected data of 1,765 consecutive patients with newly diagnosed high-grade osteosarcoma of bone who were registered in the neoadjuvant Cooperative Osteosarcoma Study Group studies and identified 24 patients (1.4%) with unequivocally proven skip metastases. All 24 patients were treated by an aggressive surgical approach coupled with polychemotherapy. Demographic, diagnostic, tumor, and treatment-related variables and response and survival data were analyzed. Results Skip metastases were identified preoperatively in 11 of 24 patients by bone scan, eight of 22 patients by plain x-ray, 15 of 18 patients by magnetic resonance imaging, and five of 10 patients by computed tomography. A complete surgical remission (CSR) of all clinically detectable tumor sites was achieved in 22 of 24 patients during front-line therapy. With a median follow-up time of 4.4 years (8 years for survivors) from diagnosis, 12 patients were alive, all of whom were in continuous CSR. Survival did correlate with location of skip metastases and histologic response to neoadjuvant chemotherapy. Conclusion Synchronous regional bone metastases are rare in osteosarcoma, and preoperative detection relies on appropriate diagnostic imaging. Aggressive multimodal therapy holds the promise to achieve prolonged survival, especially in patients in whom these metastases occur within the same bone as the primary lesion and whose tumors respond well to chemotherapy.