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Superior Vena Cava Syndrome: A Cancer-Related Medical Emergency
(More PulmCCM Topic Updates)
Multiple cancers are expected to rise in prevalence in the U.S. over the coming decades, and so is the risk for cancer-related medical emergencies. For a few, superior vena cava syndrome (SVC syndrome) will be the first manifestation of their cancer. It's important to be able to recognize and treat these oncologic emergencies; some key points on superior vena cava syndrome are highlighted here, thanks to Michael McCurdy and Carl Shanholtz's review in the July 2012 Critical Care Medicine.
- Acute Tumor Lysis Syndrome
- Hypercalcemia of Malignancy
- Spinal Cord Compression by Cancer
- Malignant Pericardial Disease
Superior Vena Cava Syndrome (SVC Syndrome)
What It Is:
Obstruction of flow through the superior vena cava into the right atrium; hence its other name, superior vena cava obstruction syndrome.
What Causes SVC Syndrome (Who Gets It?):
Superior vena cava syndrome is caused by compression or invasion by mediastinal masses (tumors and/or lymphadenopathy), stenosis of the SVC, or thrombosis.
In the pre-antibiotic era, infections (tuberculosis) were the most common cause of superior vena cava syndrome. By the 1980s, malignancy accounted for 90% of the cases of SVC syndrome. With the increase in the placement of catheters in the large vessels over recent decades, line-related thrombosis, vessel stenosis and other benign causes like fibrosing mediastinitis now account for an estimated 20-40% of cases of SVC syndrome.
Infection-related SVC syndrome: Tuberculosis, histoplasmosis and the infectious sequela fibrosing mediastinitis are uncommon causes of superior vena cava syndrome in the U.S., but still occur.
Malignancy-related SVC syndrome: Lung cancer and non-Hodgkin lymphoma together cause about 95% of cancer-related superior vena cava syndrome. About 2-4% each of patients with lung cancer or non-Hodgkin lymphoma will develop SVC syndrome during their illness. Puzzlingly, Hodgkin lymphoma rarely causes SVC syndrome despite its often affecting the mediastinal lymph nodes.
Thrombosis-related SVC syndrome: Placement of intravenous catheters in the large vessels is believed to be causing an increasing proportion of cases of superior vena cava syndrome, although precise numbers are hard to come by because the absolute risk for any given catheter placement is extremely low (hundreds of thousands of central venous lines are placed in the U.S. each year, for example). Many cases of line-related thrombosis causing superior vena cava occur in hypercoaguable cancer patients.
Collateral vessels can dilate and proliferate in response to a slow obstruction of flow through the superior vena cava, resulting in a compensated state for weeks before symptoms develop.
What To Look Out For in Suspected Superior Vena Cava Syndrome:
Facial edema is the most common symptom of superior vena cava syndrome. This can be subtle; a patient may describe feeling bloated or "puffy." Venous distension in the neck may be present on exam.
In patients with malignancy, dyspnea, cough, chest and shoulder pain, and hoarseness are more commonly noted than in "benign" compression. Dyspnea may be worse when leaning forward or lying down. Arm swelling is another common symptom of SVC syndrome.
What To Do for Superior Vena Cava Syndrome:
Although superior vena cava syndrome has been traditionally regarded as a medical emergency, authors imply it should perhaps be reclassified most often as an urgency, with time for deliberation and testing to guide thoughtful decision-making. Before rushing the patient with "typical" SVC syndrome to radiation therapy, consider that the resulting tissue necrosis could make a biopsy uninterpretable and seriously compromise the diagnosis and management of cancer, if present. (This assumes that frank airway obstruction or cerebral edema are not present -- two situations in which superior vena cava syndrome is a true emergency and immediate radiation therapy and/or stent placement are essential.)
Diagnosing the underlying cause of superior vena cava syndrome is essential, whenever possible, because many causes of SVC syndrome are benign. A contrast-enhanced CT scan of the chest is the most useful imaging study. Authors advise the careful use of selected invasive diagnostic procedures such as cytology of sputum and/or bronchial washings, thoracentesis for pleural effusions, and needle biopsy of any palpable lymph nodes. They do not mention bone marrow biopsy, but some would say suspicion for lymphoma should make this a consideration. Standard physician thinking has been that intrathoracic or transthoracic needle biopsies in patients with SVC syndrome generally carry an unacceptable risk for life-threatening bleeding, but each patient's situation should be considered individually.
Specific interventions employed for superior vena cava syndrome include:
Endovascular stents: Self-expandable stents are highly effective at relieving the symptoms of superior vena cava syndrome. Over 90% of patients report symptom relief after stent placement, and the technical success rate of placement is greater than 95%. Multiple stents may need to be placed in series (so-called “kissing stents”). Stents may even be placed in a superior vena cava that is totally occluded or contains thrombus; catheter–directed thrombolysis, balloon angioplasty, or mechanical thrombectomy may be required prior to stent placement.
Superior vena cava stents have the advantage of not requiring a diagnosis prior to implementation. Complication rates of placement are 3-7%, but potentially catastrophic (infection, pulmonary embolus, stent migration, bleeding, or perforation of the SVC); SVC stents should therefore be reserved for patients who require urgent or emergent intervention due to symptoms. Most other patients can be managed more conservatively, for example with chemotherapy and/or radiation, if malignancy is the cause of SVC syndrome.
Short-term anticoagulation is provided at many centers after SVC stent placement. Whether long-term anticoagulation is needed or helpful after stent placement not due to SVC thrombus is unknown. Some authors have recommended warfarin for months; others suggest antiplatelet therapy alone.
Chemotherapy: Initial chemotherapy is the treatment of choice for superior vena cava syndrome due to small cell lung cancer, non-Hodgkin lymphoma, or germ cell cancers. Radiation therapy is not used alone in these patients, and could possibly be counterproductive.
Patients with non-small cell lung cancer (NSCLC) with SVC syndrome do not respond well to chemotherapy, and are usually managed with radiation therapy and/or endovascular stent.
Radiation therapy: Most patients with superior vena cava syndrome due to cancer have radiation sensitive tumors. Radiation therapy can result in rapid improvement in patients with SVC syndrome due to lung cancer, in less than 72 hours usually. Some patients may require weeks to respond to radiation, and about 20% of patients with SVC syndrome do not achieve symptomatic benefit from radiation therapy.
Catheter-directed thrombolytic therapy: Has been employed on a case by case basis to treat obstruction of the superior vena cava due to thrombus. Anecdotal reports suggest effectiveness, but the true benefits and risks in SVC syndrome due to thrombus are unknown.
Glucocorticoids: May be helpful in patients with lymphoma or thymoma or other steroid–responsive malignancies. Steroids are not recommended for use in patients with superior vena cava syndrome due to lung cancer or other causes. Corticosteroids are commonly used prophylactically to reduce swelling during radiation therapy, but this is a separate indication (and without evidence of benefit).
Diuretics: There is no evidence to suggest that diuretics are beneficial in treating SVC syndrome, although they are commonly used.