(P 291) CASE REPORT: RADICAL EN BLOC MULTI-LEVEL SPONDYLECTOMY FOR A LOCALLY RECURRENT OSTEOSARCOMA

Objective: Present the technical challenges in extensive en bloc spondylectomy in locally advanced spinal sarcoma.

Methods: A 16-year-old male patient presents with extensive local progression of a spinal osteosarcoma. His primary symptoms are pain and worsening neurological deficits due to spinal cord compression. There is no evidence of metastatic disease. Initially diagnosed with a sarcoma of the spine at age 14, his first biopsy showed small blue round cell histology, although no EWSR1, CIC nor BCOR translocation had been detected. Subsequent biopsies, revealed osteoid, suggesting the diagnosis of osteosarcoma. Targeted RNA sequencing revealed, a novel YAP1::NUTM2B fusion in the tumor, which has been described elsewhere in more detail. (PMID: 38738521) Initial treatment consisted of induction chemotherapy (Protocol EE2012), a total en bloc spondylectomy of the 12th thoracic vertebra, and adjuvant chemoradiotherapy with proton therapy (45Gy, 25x1.8Gy). A postoperative thoracic chyle leak was managed with lipiodol injections. Six months later, follow-up imaging showed a local recurrence. A re-challenge with ifosfamide-etoposide resulted in a mixed response, leading to a switch to the EURAMOS protocol, followed by debulking surgery and conventional radiotherapy (70Gy, 35 x 2Gy). Despite these efforts, he presented with further multifocal progression of the local recurrence two years post diagnosis. He developed bladder dysfunction and progressive muscle weakness in the lower extremities. Because of the clinical course with aggressive local disease but without metastatic radical en bloc resection of the local recurrence was considered. After extensive evaluation and consultation with pediatric oncologists, surgeons, and rehabilitation physicians, the decision was made to proceed with surgery.

Results: The patient was positioned prone in a Gardner-Wells traction clamp. Screws were implanted at T2-8 and L4-ilium using CT navigation, and a stabilization rod was placed to support the spine. An elliptical excision of the scar was performed, and the thorax was opened at the 9th intercostal space. Ribs 9-12 were divided, a laminectomy was performed at the 9th thoracic vertebra, and the spinal cord was transected between T8 and T9. The 8th thoracic and 3rd lumbar discs were resected, the retroperitoneal space was opened, and the diaphragm was divided. The tumor was removed en bloc. The diaphragm and posterior thoracic pleura were reconstructed with a Gore-Tex mesh. An arteriovenous loop was created with a saphenous vein graft, and the posterior renal fascia was reconstructed with marlex mesh. The anterior vertebral column was reconstructed with a structural femoral semicircular allograft with the monocortical tibial bone graft press-fit into it, and the posterior column was reconstructed with four titanium rods. This phase lasted 18 hours with a blood loss of 2500 ml. The following day, a free myocutaneous anterolateral thigh (ALT) flap was transplanted onto the arteriovenous loop. This stage took 8 hours with limited blood loss. The postoperative course was complicated by ALT flap failure leading to multiple revisions and urosepsis. All analgesics were stopped two months postoperatively. He was discharged from the hospital after 78 days. Pathology showed negative resection margins. Six months after surgery, the first oncologic follow-up showed no local recurrence or metastatic disease. He has no invalidating neuropathic pain and is regaining self-sufficiency.

Conclusion: Extensive en bloc spondylectomy is feasible but should be performed by experienced multi-disciplinary teams. Multi-visceral resections and transection of the spinal cord, although highly morbid, can be considered in selected cases. We believe that the diaphragm should be adequately reconstructed to prevent herniation of abdominal organs, which may lead to obstruction or pulmonary complications. In spite of the high morbidity of the procedure, the goals of reaching symptom and tumor control have been achieved and the patient is happy.