Chemotherapy — Systemic Drug Treatment for Cancer

Chemotherapy encompasses a broad class of pharmacologic agents that disrupt the cellular division cycle. Because malignant cells replicate more rapidly and with fewer genetic repair mechanisms than most healthy cells, they are selectively vulnerable to cytotoxic compounds. These drugs act through varied biochemical mechanisms, including damaging DNA strands, inhibiting cellular replication enzymes, or preventing structural spindle formation during mitosis.

Depending on the clinical context, chemotherapy may be prescribed as a primary definitive therapy, as neoadjuvant treatment to shrink tumours prior to surgical resection, or as adjuvant therapy to eradicate microscopic residual disease. It is often scheduled in repeated cycles, allowing healthy tissues adequate recovery intervals between doses to manage toxicities.

Chemotherapy frequently forms the backbone of comprehensive cancer care. Deciding to undergo chemotherapy involves weighing anticipated therapeutic benefits against potential short-term and long-term side effects. Understanding your specific regimen empowers you to anticipate scheduled treatment cycles, monitor for predictable adverse effects, and discuss supportive medications such as anti-emetics. Together with your clinical team, you can establish realistic goals of care, whether aiming for long-term remission, symptom management, or life extension.

Before starting chemotherapy, complete blood counts, renal function panels, and liver function assays are checked to verify physiological fitness. Cardiac evaluations, such as echocardiograms, may be required for anthracycline-based regimens. Pharmacogenomic testing, including DPYD gene testing before 5-fluorouracil or capecitabine and UGT1A1 testing prior to irinotecan, helps identify metabolic variations that elevate severe toxicity risks, enabling tailored dose adjustments.

Chemotherapy is widely utilised across haematological malignancies and solid tumours. It is a cornerstone in treating leukaemias, lymphomas, breast cancer, colorectal cancer, ovarian cancer, and small cell lung cancer. In some malignancies, such as testicular cancer and Hodgkin lymphoma, chemotherapy provides high cure rates even in advanced stages. In other advanced solid tumours, it serves to control tumour burden and improve quality of life.

Chemotherapy is frequently combined with other therapeutic modalities. In chemoradiotherapy, it acts as a radiosensitiser to augment the local effect of radiation. It is also routinely paired with targeted therapies or checkpoint inhibitor immunotherapies to enhance anti-tumour responses. When toxicities such as cytopenias arise, supportive medications like granulocyte colony-stimulating factors may be administered, or chemotherapy dosages may be modified to ensure patient safety.