Best Answer: Chemotherapy is basically targeting cancer cells to inhibit growth or for complete destruction, but healthy cells are also affected this way. Immunotherapy is basically strengthening the immune system to fight against infection. In relation to oncolgy, oncology patients are prone to infection (due to limited number of WBCs which fight off infections) and so they are given a boost for their immune system. Most oncology patients do not die from cancer itself but from acquired infection due to the body's inability to protect against it.