Targeted Therapy

Targeted therapy is a class of anti-cancer treatment that acts on specific molecules involved in tumor growth, progression, and spread. Rather than broadly affecting all rapidly dividing cells as conventional chemotherapy often does, it is designed to interact with defined molecular targets that a tumor depends on. The distinction is not absolute—some targeted agents act on targets present in normal cells too—and such therapy is often combined with surgery, radiation, or other systemic treatment.

Most targeted therapies are built upon molecular targets, including proteins on or inside the cell (such as growth-factor receptors), kinase enzymes that relay growth signals, regulators of the cell cycle or programmed cell death, and blood-vessel-forming factors that feed the tumor. Determining the right target relies on molecular testing that reveals whether a tumor harbors a specific mutation, amplification, or overexpression.

Small-molecule inhibitors are compounds typically taken by mouth that can enter cells and reach intracellular targets such as tyrosine kinases. They block the signaling that drives cancer-cell division, for example inhibitors of the epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), and others. Their selection depends on accurate molecular test results, and their efficacy and side effects vary between patients.

Monoclonal antibodies are designed proteins that bind to specific targets on the surface of cancer cells. They can block growth signals, tag cancer cells for recognition by the immune system, or deliver a toxic payload directly to the tumor. They are usually given by intravenous infusion or subcutaneous injection and act through mechanisms distinct from those of small-molecule inhibitors.

Biomarkers are central to targeted therapy: they help identify who is more likely to benefit from a specific treatment and who may not gain enough benefit or may face side effects without a clear advantage. They are measured on tissue or liquid samples and include gene mutations, copy-number changes, and protein-expression levels. Clinical decisions based on them must be made within the full diagnostic context and under specialist supervision.

Despite initial effectiveness, tumors may become resistant to targeted therapy over time. Resistance arises through multiple mechanisms—for example new mutations in the target that prevent drug binding, activation of alternative survival pathways, or changes in gene regulation. This has driven sequential treatment strategies, and repeat sampling/testing may be performed to guide the next options.