Brain cancer may cause fatigue because of the tumor’s effect on the organ. This is very difficult to treat until the overall prognosis improves. Usually, it takes about six months for patients to recover from extreme tiredness. Meanwhile, other factors may trigger fatigue too.
Unsurprisingly, a brain cancer diagnosis often causes stress and this may result in fatigue. Furthermore, other symptoms like cognitive difficulties and eating problems may have the side-effect of tiredness. Often several signs of brain cancer relate to and influence each other. (via The Brian Tumor Charity)