Chemo-Nonresponsive Telangiectatic Osteosarcoma With Oligometastatic Recurrence Managed With Multimodality Therapy Including Stereotactic Ablative Body Radiotherapy (SABR): A Case Report With a Pathologic Treatment Effect.

Osteosarcoma is an aggressive primary bone malignancy that predominantly affects children, adolescents, and young adults. Outcomes remain poor for patients with high-risk features such as limited histopathologic response to neoadjuvant chemotherapy and early metastatic relapse. Other poor prognostic factors are a large tumor size, local recurrence, and pulmonary metastases. We report a young adult male with a large telangiectatic osteosarcoma of the ulna with minimal necrosis after neoadjuvant methotrexate, doxorubicin (Adriamycin), and cisplatin (MAP), who declined further systemic chemotherapy after definitive surgery. He subsequently developed early pulmonary metastases and later bilateral adrenal metastases, managed with repeated metastasis-directed interventions guided by multidisciplinary tumor board deliberations and patient-centered decision-making. A notable feature of this case is the use of modern radiotherapy, including preoperative stereotactic body radiotherapy (SBRT) for a locally recurrent right adrenal bed lesion, followed by surgical resection and intraoperative radiotherapy. The SBRT used high fraction sizes of 8 Gy per fraction and was described as stereotactic ablative body radiotherapy (SABR). Histopathologic evaluation of the resected specimen demonstrated an extensive treatment effect with no viable tumor cells. Over nearly a decade of follow-up, the patient has maintained prolonged survival and good quality of life despite multiple recurrences and an initial lack of chemosensitivity. This case highlights how integrated, patient-centered multimodality care can be applied in complex osteosarcoma and provides pathologic evidence consistent with a marked SABR treatment effect in an adrenal tumor bed recurrence. These observations are hypothesis-generating and support further study in selected osteosarcoma settings.