Immunotherapy is a promising new approach to cancer treatment that uses a series of precision strikes to disintegrate cancer from within the body itself. Doctors use gene therapy to train a patient’s immune system to recognize and destroy their cancer in the same way it dispatches bacteria and viruses. The therapy can be very powerful because the “drug” are cells churned out by the patients themselves. If the treatment succeeds, the body gets trained to keep on treating itself, ideally for a lifetime.