Can mechanical ventilation aid lung cancer patients?

Not really: Mechanical ventilation is to assist patients whose lungs are so sick they can't breathe adequately on their own. There is no advantage from a lung cancer perspective to be on a ventilator.

Depends: If they have just had surgery or have a treatable pneumonia, yes. If they have respiratory failure from the cancer, it is simply prolonging the dying process.

No: It is not a cancer treatment. Occasionally it may be needed during lung cancer treatment (as in some cases after lung resection) but it is a supportive treatment.