OncologyTier 1Disease (DEADMAN)

Metastatic disease manifestations - superior vena cava (SVC) obstruction

Description

Obstruction of SVC flow -> venous hypertension in the head, neck and upper limbs
Rarely an immediate emergency - collaterals develop over weeks
- *The exceptions: stridor from airway compromise, and cerebral oedema with altered conscious state - these are emergencies*
Getting tissue before treating is usually the priority, because the commonest causes (SCLC, lymphoma, germ cell tumour) are exquisitely treatment-sensitive and steroids/radiotherapy destroy diagnostic material

~15,000 cases/yr in the US; incidence rising with intravascular devices
~60-90% malignant
- NSCLC ~50% (commonest overall by volume)
- SCLC ~25% (highest proportional risk - central, bulky)
- Lymphoma ~10% (esp. primary mediastinal B-cell, lymphoblastic)
- Germ cell tumour, thymoma, mesothelioma, metastatic (breast, colon)
Benign causes now ~10-40% and rising: indwelling central lines and pacemaker leads - the commonest benign cause

SVC is thin-walled, low-pressure, and surrounded by rigid structures (sternum, trachea, right main bronchus, aorta, nodes) -> easily compressed
Three mechanisms:
- Extrinsic compression - tumour or nodes (commonest)
- Intraluminal thrombus - catheter-associated, or superimposed on external compression
- Direct invasion of the vessel wall
-> venous hypertension -> collaterals via azygos, internal mammary, lateral thoracic and vertebral venous plexuses
- Collateral development explains why a slowly growing tumour may be almost asymptomatic while acute thrombosis is dramatic
Obstruction above the azygos entry is better tolerated than below it

Non-malignant causes

Clinical

Facial, neck and upper limb swelling; facial plethora and cyanosis
Distended neck veins that are non-pulsatile and have no visible waveform - the discriminator from raised JVP in heart failure
Distended chest wall collateral veins (look at the anterior chest with the patient undressed)
Periorbital oedema, chemosis and conjunctival injection, distended retinal veins on fundoscopy, exophthalmos
Dyspnoea (commonest symptom), cough, hoarseness, dysphagia
Pemberton's sign - arms raised above the head for 1 minute -> facial plethora, raised JVP, distended head and neck veins, inspiratory stridor
Worse lying flat and on bending forward

Red flags demanding immediate treatment

Investigation

CXR - mediastinal widening, mass, right hilar mass, unilateral pleural effusion (suggests malignancy)
- Normal in ~15%
CT chest with IV contrast is the investigation of choice
- Defines SVC patency, level and length of obstruction, extrinsic vs intraluminal, collaterals, and the causative mass
- Guides biopsy route and stent planning
Get tissue: sputum cytology, pleural fluid, peripheral node biopsy, EBUS/bronchoscopy, mediastinoscopy, CT-guided core biopsy
Tumour markers if germ cell tumour possible (AFP, beta-hCG - can spare a young man a biopsy)
Doppler of upper limb veins if catheter thrombosis suspected

A. Supportive - immediately, for everyone

Sit upright, oxygen
Avoid upper limb IV access and venepuncture on the affected side
Corticosteroids: benefit is unproven except in lymphoma and thymoma - *withhold until tissue is obtained* if lymphoma is possible (steroids lyse lymphoma and destroy the diagnosis)
Diuretics give symptomatic relief but no evidence of benefit; avoid volume depletion

B. Establish the diagnosis before definitive therapy

*This is the single most important management decision*
Exception: airway compromise or cerebral oedema -> stent or radiotherapy first

C. Definitive treatment

Situation	Treatment
SCLC, lymphoma, germ cell tumour	Chemotherapy - rapid response, often within days
NSCLC, other solid tumours	Radiotherapy +/- chemotherapy
Severe symptoms, or refractory/recurrent obstruction	Endovascular stent - relieves symptoms within 24-72 h, the fastest option
Catheter-associated thrombus	Anticoagulation; remove the line if infected or non-functional (a functioning line may be retained with anticoagulation)

SVC stenting
- Highest and fastest symptom relief; can be done before histology in a crisis
- Complications: stent migration, infection, pulmonary embolism, perforation
- Anticoagulate after stenting
Anticoagulation is not routine for extrinsic compression without thrombus
Surgical bypass is reserved for benign disease refractory to stenting

Lung cancer - small cell (proportionally highest risk), non-small cell
Lymphoma - primary mediastinal large B-cell, lymphoblastic, Hodgkin
Germ cell tumour, thymoma, mesothelioma
Metastatic breast and colorectal cancer
Central venous catheters, PICC lines, pacemaker and ICD leads - the leading benign cause
Fibrosing mediastinitis (histoplasmosis, TB), IgG4-related disease, sarcoidosis
Post-radiation mediastinal fibrosis
Retrosternal goitre, thoracic aortic aneurysm
May coexist with pericardial effusion/tamponade and tracheal compression - look for all three

Symptoms usually improve within 1-2 weeks of effective treatment; collaterals persist
Stenting relieves symptoms in >90% within 24-72 hours
Prognosis is determined by the underlying cause, not by the SVC obstruction itself
- Lymphoma and germ cell tumour: potentially curable
- SCLC: excellent initial response, median survival still <12 months
- NSCLC: median survival ~6 months once SVC obstruction develops
- Benign/catheter-related: excellent
Recurrence ~10-20% after radiotherapy, lower after stenting
Complications: laryngeal and cerebral oedema, thrombosis extending into subclavian/jugular veins, stent thrombosis or migration

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