Each case would obviously be individualized and as I mentioned this decision is usually made by the medical oncologist. Because if you have an elderly patient, one, the chemotherapy will not be as effective, so you don't usually try it. In a younger patient, you will do anything to try and prolong survival. So they get everything. After all the purpose of it is to kill living cells.
Chemotherapy is designed to kill the cells that divide the fastest.
These are usually the cancer cells. But some normal healthy cells in the body will also be killed by the chemotherapy. That is why many patients get ill while undergoing it. Common side effects, nausea, vomiting and hair loss. Sometimes the chemotherapy will effect a patient's bone marrow.