21st June 2023

Superior Vena Cava Obstruction (SVCO)

Aetiology

Malignant SVCO can arise from a number of different mechanisms. These include extrinsic compression from an adjacent tumour, whether from a primary lung/mediastinal tumour or from locoregional lymphadenopathy. There can also be direct invasion into the superior vena cava from adjacent malignancy and obstruction secondary to malignancy-associated thrombosis or embolism.

The most common malignancies associated with SVCO are lung cancers, particularly small cell carcinoma (found in 10% of these patients) as well as non-small cell lung cancer (2-4% of these patients). Typically, tumours sited in the right upper lobe pose the greatest risk due to their anatomical location. Lymphomas are also a common cause, in particular diffuse large B-cell lymphoma (DLBCL) and primary mediastinal large B-cell lymphoma. Other malignancies of the mediastinum including thymoma, thymic carcinoma, germ-cell tumours and mesothelioma contribute to the remaining causes.

The archetypal presenting symptoms include upper limb, neck and facial swelling, dyspnoea, and chest discomfort. These symptoms may be further aggravated by leaning forward. Persistent swelling can lead to oedema of the larynx, leading to stridor and dysphagia. Furthermore, patients can develop cerebral oedema leading to headaches, confusion, and brainstem herniation. Thankfully, due to the greater availability of early imaging, these severe sequelae (airway compromise and cerebral oedema) are becoming increasingly rare. Depending on the underlying tumour biology, the development of SVCO tends to be gradual, which typically allows for the patient to develop venous collaterals, allowing the patient to compensate.

Most patients will have an abnormal chest x-ray. Further imaging in the haemodynamically stable patient is with cross-sectional imaging i.e. CT thorax or MRI (particularly in the case of a ‘Pancoast’ tumour). Duplex ultrasonography can be useful in determining the coexistence of thrombus. Dedicated venography (CT/MRI) may have an application in the planning of endovenous recanalisation. In those patients without a tissue diagnosis, it is imperative that this is sought, and this may be done concurrently with initial management.

Management

The management of malignant SVCO is dependent on the severity of the symptoms and the underlying biology of the malignancy. In those patients presenting in extremis, urgent SVC stenting should be sought via Interventional Radiology. It may be possible for a tissue diagnosis to be obtained at the same time. In patients who present with mild-moderate symptoms, the management should be tissue-directed. In those patients with known chemosensitive disease e.g. small cell lung cancer, germ-cell etc, early chemotherapy may be the treatment of choice. In those patients with less sensitive disease, exploration of SVC stenting should be sought in the first instance and where this is not possible, palliative radiotherapy should be considered.

The use of glucocorticoid steroids is not evidence-based but is commonly employed. They can be used for steroid-responsive conditions such as lymphoma or concurrently with radiotherapy. However, in patients with mild-moderate symptoms it is important to remember that in those patients lacking a tissue diagnosis, a biopsy should be prioritised. This is particularly relevant in the case of suspected lymphoma, where early administration of steroids will provide a rapid clinical response, at the expense of obtaining a tissue diagnosis. This would ultimately lead to delays in diagnosis and subsequent definitive management. The concurrent use of anticoagulation should be employed in patients with confirmed thrombosis, however, prophylactic use is debated and so no consensus statement can be offered on its empirical use.