Chapter 37 svco

general oncology from devita presentation

1. Superior vena cava syndrome:

2. Superior vena cava (SVC) syndrome results from any condition that leads to obstruction of blood flow through the SVC. Obstruction can be caused by invasion or external compression of the superior vena cava by adjacent pathologic processes involving the right lung, lymph nodes, and other mediastinal structures, or by thrombosis of blood within the SVC . In some cases, both external compression and thrombosis coexist 

3. In the preantibiotic era, syphilitic thoracic aortic aneurysms, fibrosing mediastinitis , and other complications of untreated infection were frequent causes of the SVC syndrome. In the postantibiotic era, malignancy became the most common cause. More recently, the incidence of SVC syndrome due to thrombosis has risen, largely because of increased use of intravascular devices such as catheters and pacemaker wires.

4. PATHOPHYSIOLOGY  —  Obstruction of the SVC can be caused by invasion or external compression by adjacent pathologic processes involving the right lung, lymph nodes, or other mediastinal structures , or by thrombosis of blood within the SVC. As the flow of blood within the SVC becomes obstructed, venous collaterals form, establishing alternative pathways for the return of venous blood to the right atrium.

5. Collateral veins may arise from the azygos , internal mammary, lateral thoracic, paraspinous , and esophageal venous systems. The venous collaterals dilate over several weeks. As a result, upper body venous pressure is markedly elevated initially but decreases over time. However , even when well-developed collateral drainage patterns are present, central venous pressures remain elevated, producing the characteristic signs and symptoms of SVC syndrome.

6. The rapidity of onset of symptoms and signs from SVC obstruction depends upon the rate at which complete obstruction of the SVC occurs in relation to the recruitment of venous collaterals . Patients with malignant disease may develop symptoms of SVC syndrome within weeks to months because rapid tumor growth does not allow adequate time to develop collateral flow.

7. The interstitial edema of the head and neck is visually striking but generally of little clinical consequence. However , edema may narrow the lumen of the nasal passages and larynx, potentially compromising the function of the larynx or pharynx and causing dyspnea , stridor , cough, hoarseness, and dysphagia . In addition, cerebral edema can also occur and lead to cerebral ischemia, herniation , and possibly death . Cardiac output may be diminished transiently by acute SVC obstruction, but within a few hours, blood return is reestablished by increased venous pressure and collaterals.

8. Hemodynamic compromise, if present, more often results from mass effect on the heart than from SVC compression 

9. Etiology : Malignancy  —  An intrathoracic malignancy is responsible for 60 to 85 percent of cases of SVC syndrome. Non-small cell lung cancer (NSCLC) is the most common malignant cause of SVC syndrome, accounting for 50 percent of all cases , followed by small cell lung cancer (SCLC, 25 percent of all cases) and non-Hodgkin lymphoma (NHL, 10 percent of cases). Together , lung cancer and NHL are responsible for approximately 95 percent of cases of SVC syndrome that are caused by malignancy .

10. Lung cancer   —  Approximately 2 to 4 percent of patients with lung cancer develop SVC syndrome at some point during their disease course . SVC syndrome is more common with SCLC, occurring in approximately 10 percent of cases at presentation. This is presumably because SCLC develops and grows rapidly in central rather than peripheral airways. Fewer than 2 percent of patients presenting with NSCLC have SVC syndrome as a complication, but because of the higher incidence, NSCLC is a more frequent cause of SVC syndrome than is SCLC . Venous obstruction in these cases results from extrinsic compression of the SVC by either the primary tumor or enlarged mediastinal lymph nodes, or as a result of direct tumor invasion of the SVC .

11. Lymphoma  —  SVC syndrome develops in 2 to 4 percent of cases of NHL. Diffuse large cell and lymphoblastic lymphomas are the most common subtypes that are associated with SVC syndrome. SVC syndrome is even more common in patients with primary mediastinal large B-cell lymphoma with sclerosis, an unusual and aggressive NHL subtype that represents 3 to 7 percent of all diffuse large-cell lymphomas. Patients typically present with a rapidly enlarging anterior mediastinal mass, frequently with associated SVC syndrome .

12. Although most NHLs cause SVC syndrome by extrinsic compression due to enlarged lymph nodes , patients with intravascular ( angiotropic ) lymphoma have intravascular occlusion as the primary pathogenic mechanism . Other  — Other malignant tumors that are less commonly associated with the SVC syndrome include : thymoma , primary mediastinal germ cell neoplasms , mesothelioma , and solid tumors with mediastinal lymph node metastases ( eg , breast cancer)

13. Nonmalignant disorders   —  Nonmalignant conditions account for 15 to 40 percent of SVC obstructions. Although the incidence of SVC syndrome due to infections such as tuberculosis and syphilis has decreased, there has been an increase in SVC thrombosis associated with the presence of intravascular devices such as central venous catheters and cardiac pacemaker leads 

14. Clinical maniestations : Regardless of etiology, dyspnea is the most common symptom . In addition, patients frequently complain of facial swelling or head fullness, which may be exacerbated by bending forward or lying down. Other symptoms include arm swelling, cough, chest pain, or dysphagia . Patients with cerebral edema may have headaches, confusion, or possibly coma .

15. On physical examination, the most common findings are facial edema and venous distension in the neck and on the chest wall . Arm edema, cyanosis, and facial plethora can be seen. In most cases, symptoms are gradually progressive over several weeks and then get better over time, due to the development of venous collaterals.