By Your Powers Combined: Treating Pelvic Osteosarcoma With Combination Radiation and Thermoablation

A 77-year-old man with a history of diabetes, atrial fibrillation, heart failure with preserved ejection fraction, and class III obesity presented with 6 months of right groin pain. MRI showed a 10.5 × 6.9 × 12.1-cm tumor of the right pubis and ischium with soft-tissue extension involving the femoral acetabular joint, pelvic sidewall, obturator internus, adductor muscles, and abutting the prostate gland (Fig. 1). Core-needle biopsy confirmed a high-grade osteosarcoma. A positron emission tomography/computed tomography scan demonstrated a fluorodeoxyglucose-avid lesion without distant metastases (stage III, T3bN0M0). Standard-of-care treatment involves neoadjuvant chemotherapy, surgical resection, and adjuvant chemotherapy, with associated 5-year survival rates of approximately 37%. 1 Brown JM Matichak D Rakoczy K Groundland J. Osteosarcoma of the pelvis: Clinical presentation and overall survival. Sarcoma. 2021; 20218027314 Crossref PubMed Scopus (14) Google Scholar Internal hemipelvectomy is an option, but even this limb-sparing procedure is highly invasive and carries risks of long-term morbidity and perioperative mortality. 2 Beck LA Einertson MJ Winemiller MH DePompolo RW Hoppe KM Sim FF. Functional outcomes and quality of life after tumor-related hemipelvectomy. Phys Ther. 2008; 88: 916-927 Crossref PubMed Scopus (52) Google Scholar This patient declined internal hemipelvectomy as well as chemotherapy due to his elderly status, multiple comorbidities, and toxicity risks. However, he remained interested in less-invasive cancer-directed therapies. He was managed with debulking cryoablation of the soft-tissue component of the tumor followed by 2 rounds of cooled radiofrequency ablation of the intraosseous component. External beam radiation therapy of 80 Gy in 40 daily fractions was delivered with intensity-modulated radiation therapy technique (Fig. 2). The patient had improved pain posttreatment and was able to do pool exercises once more, although his right lower extremity remained comparatively weakened. At 13 months a positron emission tomography/computed tomography scan revealed a metastasis to the right pelvic side wall, and at 27 months additional lung metastases were found, despite achieving control of the primary tumor. Fig. 2Intensity-modulated radiation therapy isodose distribution with a prescription of 80 Gy to the gross tumor with a 5-mm planning target volume margin. View Large Image Figure Viewer Download Hi-res image Download (PPT)