What if the path to curing cancer has been part of the body all along? For generations the three pillars of cancer treatment have been surgery, radiation, and chemotherapy. But both chemotherapy and radiation are crude weapons with significant collateral damage to healthy tissue, and surgery can leave cancerous cells behind. Scientists have long tried to understand how to get the immune system—the body's natural defense mechanism—to recognize cancer cells as the enemy and destroy them. And now we may finally be turning the corner: Doctors are finding that clinical regimens known as immunotherapies can empower a patient's immune system to fight the disease like it might an infection, while sparing a person's normal cells.