Immunotherapy harnesses the body’s own immune system to recognize and destroy cancer cells. The most widely used class is immune checkpoint inhibitors — antibodies targeting PD-1, PD-L1, or CTLA-4 — that release natural brakes on T cells, enabling them to attack tumors. Unlike chemotherapy or targeted therapy, immunotherapy can produce durable, long-term remissions that persist years after treatment ends, even in advanced metastatic disease. Responses are enriched in patients whose tumors express predictive biomarkers such as PD-L1, high tumor mutational burden (TMB-H), or microsatellite instability (MSI-H/dMMR). Combination approaches with chemotherapy, targeted agents, or radiation continue to expand the受益 patient population.