Osteosarcoma Arising After Ewing Sarcoma or Vice Versa: A Report of 20 Affected Patients from the Cooperative Osteosarcoma Study Group (COSS).

BACKGROUND/AIM: Ewing sarcoma can arise in patients after osteosarcoma or vice versa. Our aim was to learn more about which patients develop these secondary tumors, which treatments may be effective, and which patients might survive. PATIENTS AND METHODS: The database of the Cooperative Osteosarcoma Study Group (1980-09/2022) was searched for all patients with an osteosarcoma (including undifferentiated pleomorphic sarcoma of the bone) who also suffered from Ewing sarcoma (incl. peripheral neuroectodermal tumor) at any time, previously or thereafter. The identified patients were then analyzed for patient, tumor, and treatment-related variables as well as their disease- and survival-status at the last follow-up. RESULTS: A total of 20 eligible patients [17 Ewing sarcoma prior to osteosarcoma, 3 vice versa; 10 males, 10 females; median age at 1st cancer 10.5 (2.4-20.6), at 2nd cancer 20.5 (9.9-42.4) years] were identified. None of the patients developed a 3rd cancer and none had a known tumor-predisposition syndrome. Sixteen/17 secondary osteosarcomas and no secondary Ewing sarcoma developed in sites that had previously been irradiated. Nineteen/20 (95%) patients received primary multi-agent chemotherapy for their 1st and 2nd cancers. Actuarial overall and event-free survival probabilities at five years after the diagnosis of the secondary cancer were 69% and 42%, respectively. CONCLUSION: Secondary osteosarcoma arising after Ewing sarcoma is almost exclusively associated with radiation. This is not the case vice versa. Either way, long-term survival is a realistic possibility with appropriate multidisciplinary treatment; thus, therapeutic negligence is clearly inadequate.