I was involved in helping to manage pain in a cancer patient recently. The case was made more complex because of the shortness of breath the the patient was experiencing.
Breathlessness in the ill patient with cancer can be challenging to manage. Every patient and their family should be reassured as the experience can be extremely frightening. Simple general measures can be performed like changing position and teaching breathing exercises. After excluding and treating reversible causes like an effusion (fluid collection) around the lung and heart, chest infection, anaemia and airway obstruction which make can make it mechanically more difficult to breathe, various medications can be tried including opioids, benzodiazepines and steroids. Oxygen is useful if there is low oxygen level, and sometimes bronchodilators can make a difference even in the absence of a wheeze.

Management should be multi-disciplinary with engagement of the physiotherapist, oncologist palliative physician, respiratory physician as well pain specialist.
In cases like these, I am reminded that even though we cannot always cure, we can always provide a little care, and a lot of comfort.