Need for invasive diagnostic procedures in the management of superior vena cava syndrome.

Radiation therapy is considered the first treatment of choice for thoracic malignant diseases causing superior vena cava syndrome (SVCS). However, its use is poorly documented in cases in which intravascular tumor thrombosis is the major cause of obstructive symptoms. We report two cases of SVCS caused by thoracic malignancy. The first case failed to respond to the initial course of mediastinal radiation therapy. Contrast and radionuclide venography revealed two sites of tumor thrombosis located outside the radiation portal. Irradiation of these areas resulted in prompt relief of symptoms and complete relief of obstruction. In the second case, superior venacavogram and transluminal biopsy established the diagnosis and location of superior vena cava obstruction.