Chemotherapy

Chemotherapy is the use of cytotoxic drugs to destroy or suppress the growth of cancer cells. Most regimens are systemic, but regional delivery is also used. Chemotherapy can aim to cure, to shrink tumors before other treatments (neoadjuvant), to eliminate microscopic disease after surgery (adjuvant), or to relieve symptoms in advanced disease (palliative).

Most chemotherapies interfere with cell division or DNA replication. They are traditionally classified by mechanism: alkylating agents, antimetabolites, natural products, and platinum compounds. In modern practice, chemotherapy often combines several drugs with complementary effects to improve efficacy and limit resistance; dosing is given in cycles to allow recovery of normal tissues.

Administration and monitoring: routes include oral tablets and intravenous infusion. Regimens are repeated in cycles, with planned rest periods. Treatment response is monitored by imaging and laboratory tests; blood counts and organ function are frequently checked to manage side effects.

Common side effects result from damage to rapidly dividing cells, especially bone marrow, the lining of the gut, and hair follicles. These include anemia, infection risk, mucositis, nausea, vomiting, diarrhea, fatigue, neuropathy, and hair loss. Long-term risks include reduced fertility and, rarely, therapy-related leukemia or other secondary cancers. Some agents cause organ-specific toxicity (e.g., heart, kidneys, nerves).

History and scope: The term chemotherapy emerged in the early 20th century, with pioneering work in mustard derivatives in the 1940s and 1950s. Since then, the field has evolved to include targeted therapies and immunotherapies alongside traditional cytotoxic drugs, expanding options for many cancers. Limitations include tumor heterogeneity and drug resistance, toxicity, and incomplete effectiveness in some cancers.