immunotherapy

Immunotherapy for lung cancer works not by attacking the tumor directly but by releasing the brakes on the patient's own immune system so it can recognize and destroy the cancer. Cancers often survive by displaying a kind of stand-down signal that switches off approaching immune cells. The most widely used lung cancer immunotherapies, called checkpoint inhibitors, block that off-switch so the immune cells stay active.

The immune system has natural checkpoints — molecules like PD-1 on immune cells and PD-L1 on other cells — that normally prevent it from attacking the body's own tissues. Many lung cancers exploit this by waving the PD-L1 flag to look harmless. Checkpoint inhibitor antibodies cover up these signals, in effect cutting the brake line so T cells can do their job against the tumor.

These drugs have meaningfully improved survival for many people with advanced lung cancer, both non-small-cell and small-cell types, used alone or combined with chemotherapy, and increasingly after surgery as well. How well they work relates in part to tumor features such as the level of PD-L1, though no single marker predicts the response perfectly.

A balanced caveat: because immunotherapy ramps up the immune system, it can occasionally cause it to attack healthy organs — the skin, gut, lungs, thyroid, and others — so side effects look like autoimmune inflammation and need prompt recognition and treatment.