(P 61) ADJACENT VENOUS TUMOR THROMBUS IN PRIMARY OSTEOSARCOMA OF THE PELVIS AND EXTREMITIES

Objective: Despite the high rate of venous tumor thrombus (VTT) in osteosarcoma of the pelvis, there are few descriptions of VTT associated with extrapelvic primary osteosarcoma. We sought to further describe the prevalence and presenting features of venous tumor thrombus in osteosarcoma of both the pelvis and extremities.

Methods: We reviewed 308 patients with osteosarcoma treated between 2000 and 2022 at our institution. Primary lesions were located in the upper extremity (n=40), lower extremity (n=198), or pelvis (n=70). Medical records and histopathology were reviewed to identify patients with thrombi in proximity to their primary lesion.

Results: Tumors abutted vessels in 131 cases (42.5%) and encased vessels in 30 cases (9.7%). Twenty-one patients were diagnosed with VTT (Table 1). The rate of VTT was 25% for pelvic and 1.7% for extremity osteosarcoma. The most common imaging features associated with VTT were enhancement with contrast (100%), venous enlargement (83%), vessel encasement (66%), and visible intraluminal osteoid matrix (50%). Disease-specific survival (DSS) for patients with VTT was 95% at 12 months, 49% at three years, and 31% at five years. When controlling for presence of metastatic disease, VTT was associated with worse DSS (HR 2.3, 95% CI [1.11, 4.84]) (Figure 1).

Conclusion: VTT is rare within osteosarcoma and occurs more commonly in the pelvis than the extremities. Imaging features include enhancement with contrast, venous dilation, and vessel encasement. VTT portends a worse prognosis for patients with osteosarcoma with a similar survivability to metastatic disease.