The Mandate for Chemotherapeutic Decompression in Superior Vena Caval Obstruction

Abstract

The superior vena caval syndrome has been recognized since 1757, at which time William Hunter described a case secondary to aortic aneurysm. Individual case reports have appeared since, and in the past thirty years, larger series have been reported. Despite this two-hundred-year history, uniformity of opinion as to the best method of therapy of the syndrome is still lacking. The anatomy of the superior vena cava adequately explains the clinical picture which results from obstruction or compression of this vessel. It drains venous blood from the head and neck and the thoracic wall. Of considerable importance is the fact that the lower half of the superior vena cava is enclosed within the fibrous layer of the pericardium. Its main tributary is the azygos vein which arises at the level of the renal veins and ascends the posterior mediastinum to join the superior vena cava at the level of the second costal cartilage. Obstruction to the superior vena cava may occur at three sites: (a) above the entrance of the azygos vein, with the azygos vein and proximal superior vena cava patent; (b) at the junction of the azygos vein with the superior vena cava; (c) proximal to the entrance of the azygos vein into the superior vena cava. The superior vena cava is particularly vulnerable to obstruction because it is a thin-walled, low-pressure vessel locked in a tight compartment and surrounded by nodes, bronchi, and aorta. A slowly developing obstruction such as that seen with benign lesions is tolerated well; a rapidly developing obstruction, as with malignant lesions, is tolerated poorly. The symptoms of the superior vena caval syndrome are due to venous hypertension in the areas normally drained by the vessel or its tributaries. They will vary in severity depending on the degree, location, and rapidity of the obstruction, as well as on the development of a collateral circulation. The elevated venous pressure causes edema to develop in the organs and tissues drained by the superior vena cava. A major principle of therapy, therefore, is to reduce the edema and thereby relieve most of the symptoms as rapidly as possible. This is especially so in those patients with the “wet-brain” syndrome, characterized by drowsiness, stupor, unconsciousness, and seizures. It is well established that cellular edema is one of the early tissue reactions to radiotherapy. This usually can be avoided if radiation therapy is begun with small doses which are gradually increased with the patient's response. It may take many days before an effective amount of therapy can be delivered to the tumor or to the lymph nodes causing the caval obstruction. Other measures, such as intensive diuresis with mercurials, a low-salt diet, and maintenance of the patient in a head-elevated position for as much of the time as is possible, may help to reduce the disturbing edema, but will do nothing to relieve the cause of the obstruction.