Not sure what you mean by marks. If you need a line or port yes there will be permanent marks. Many people who have intravenous chemotherapy via a peripheral cannula also have permanent marks
However marks dont effect the medical, the underlying pathology and effect of the chemotherapy do
Chemotherapy in the main is given for life threatening disease so if needed there is seldom any alternative I am afraid. It must then be declared at any future medical as to do otherwise is a criminal offense and voids any insurance. If you have been advised to have chemotherapy I would proceed and then discuss with your regulator
Good luck