Obstruction of either the central airways or superior vena cava is a complication of cancer which can cause severe breathlessness.
Although high level evidence to support these treatments is lacking, treatment guidelines recommend that for central airway obstruction causing dyspnoea, either endobronchial treatments (laser, brachytherapy, electrocautery, cryosurgery, stenting) or external beam radiotherapy may provide effective palliation. [1,2] A systematic review comparing external beam radiotherapy plus brachytherapy for obstruction with external beam radiotherapy alone showed no strong evidence to support adding brachytherapy to external beam radiotherapy. External beam radiotherapy alone seemed to be more effective than brachytherapy. 
Chemotherapy should be considered, where clinically appropriate, as the first line treatment for chemosensitive tumours causing obstruction.  There is evidence that both endovascular stenting and radiotherapy are effective in malignant superior vena cava obstruction. [1-2]