Chemotherapy: Systemic Drug Treatment to Kill Cancer Cells or Halt Division—Often Combined with Surgery, Radiation, Immunotherapy

Chemotherapy uses cytotoxic drugs that target rapidly dividing cells. It is systemic—circulating throughout the body—unlike surgery or radiation which are local.

Mechanisms

• Alkylating agents (cyclophosphamide): DNA cross-linking.
• Antimetabolites (5-FU, methotrexate): mimic nucleotides, block synthesis.
• Anthracyclines (doxorubicin): intercalate DNA, inhibit topoisomerase II.
• Taxanes (paclitaxel): stabilize microtubules → mitotic arrest.
• Platinum analogs (cisplatin): DNA adducts.
• Targeted agents (TKIs, mAbs): specific molecular targets (often combined with chemo).

Administration

• IV infusion (most common), oral, intrathecal, intraperitoneal.
• Cycles (e.g., every 2–3 weeks) allow normal tissue recovery.

Side Effects

Myelosuppression, nausea, alopecia, mucositis, neuropathy, cardiotoxicity, infertility—vary by agent. Supportive care (growth factors, antiemetics, scalp cooling) mitigates many.

Integration

Neoadjuvant (pre-surgery), adjuvant (post-surgery), definitive (with radiation), palliative. Multidisciplinary tumor boards optimize sequencing.