30th December 2024

Aetiology of SVCO

SVCO is predominantly caused by malignancy and its complications. Obstruction can be external, related to tumour mass or mediastinal lymphadenopathy, or secondary to thrombus. The causes of cancer related SVCO are summarised in Table 11.

External compression

The commonest cause of external compression is lung cancer. Non-small cell lung cancer (NSCLC) causes 50% of all SVCO, although less than 2% of patients with NSLC develop SVCO. Conversely, 15-20% of small cell lung cancer (SCLC) patients develop SVCO, however these only make up 25% of all SVCO cases, due to its lower prevalence.

Other malignancies that result in SVCO include non-Hodgkin’s lymphoma (usually driven by mediastinal lymphadenopathy) and, more rarely, thymomas or mediastinal germ cell tumours.

Superior vena cava (SVC) clots

Clots within the superior vena cava may also cause SVCO. Malignancy increases this risk due to its prothrombotic nature. Tumours that cause extrinsic compression of the SVC create turbulent flow, leading to thrombus formation. Patients receiving systemic anti-cancer therapy may have an indwelling intravascular device, such as Hickmann or PICC lines, which also increase risk of clotting.