Makhdoom Sarwar, as with any medical treatment, it comes down to discussion with the patient and what is important to them.
Some people want a long life at any cost, others want to avoid possible side effects. Again, what gives life quality is different for everyone, some people want to be free of pain, others want to be able to be around family, others get quality of life from being able to work in the garden or play sports.
There are different reasons to prescribe the same drug, this is reflected in choice of dosage and period of treatment.