targeted therapy

Targeted therapy is cancer treatment aimed at a specific molecular flaw that drives a particular tumour, rather than at all dividing cells. If classic chemotherapy is carpet-bombing everything that grows fast, targeted therapy is a guided strike at one structure the cancer depends on. The key idea is that many tumours have an addiction: a single mutated protein or signal they cannot live without.

These drugs only work if that target is actually present, so they go hand in hand with biomarker testing. A tumour might be tested for a specific mutated gene, an overactive receptor, or a fusion protein; only patients whose cancer carries the matching feature are likely to benefit. The targets are usually proteins involved in growth signalling, such as tyrosine kinases, growth factor receptors, or downstream pathway components.

Targeted therapy often spares many normal tissues and so avoids some classic chemotherapy toxicities, but it is not side-effect-free; it produces its own pattern of effects (rashes, diarrhoea, high blood pressure, organ-specific injury) because the targeted pathways also matter in healthy cells. Crucially, tumours frequently evolve resistance by mutating the target or switching to a bypass pathway, so durable control often requires combinations or successive drugs.