Che

Chemotherapy
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Chemotherapy is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents) as part of a standardized chemotherapy regimen. Chemotherapy may be given with a curative intent or it may aim to prolong life or to reduce symptoms.

History

The origins of chemotherapy can be traced back to the early 20th century. The first use of chemicals to treat cancer was in the form of mustard gas derivatives during World War II. Researchers discovered that nitrogen mustard could be used to treat lymphoma, leading to the development of other chemotherapeutic agents.

Mechanism of Action

Chemotherapy works by targeting rapidly dividing cells, a hallmark of cancer cells. However, it also affects normal cells that divide rapidly, such as those in the bone marrow, digestive tract, and hair follicles, leading to side effects.

Types of Chemotherapeutic Agents

Chemotherapeutic agents can be classified into several categories based on their mechanism of action:

• Alkylating agents: These drugs work by adding an alkyl group to the DNA, which prevents the DNA from replicating. Examples include cyclophosphamide and ifosfamide.

• Antimetabolites: These mimic the building blocks of DNA or RNA, interfering with their synthesis. Examples include methotrexate and 5-fluorouracil.

• Anti-tumor antibiotics: These interfere with DNA by inserting themselves between DNA base pairs. Examples include doxorubicin and bleomycin.

• Topoisomerase inhibitors: These interfere with the enzymes that help separate the strands of DNA during replication. Examples include etoposide and irinotecan.

• Mitotic inhibitors: These prevent cell division by inhibiting the mitotic spindle. Examples include vincristine and paclitaxel.

Administration

Chemotherapy can be administered in several ways, depending on the type of cancer and the specific drugs used:

• Intravenous (IV): The most common method, where drugs are injected directly into a vein.

• Oral: Some chemotherapeutic agents can be taken in pill form.

• Intramuscular (IM): Injection into a muscle.

• Subcutaneous: Injection under the skin.

• Intrathecal: Injection into the cerebrospinal fluid to treat cancers of the central nervous system.

Side Effects

The side effects of chemotherapy are due to its effects on normal, rapidly dividing cells. Common side effects include:

• Myelosuppression: Decreased production of blood cells, leading to anemia, leukopenia, and thrombocytopenia.

• Gastrointestinal toxicity: Nausea, vomiting, diarrhea, and mucositis.

• Alopecia: Hair loss.

• Fatigue: A common and often debilitating side effect.

• Neurotoxicity: Peripheral neuropathy and cognitive changes.

Resistance

Cancer cells can develop resistance to chemotherapy through various mechanisms, such as:

• Drug efflux: Increased expression of P-glycoprotein that pumps drugs out of cells.

• Drug inactivation: Increased metabolism of drugs to inactive forms.

• DNA repair: Enhanced ability to repair DNA damage caused by chemotherapy.

Combination Therapy

Chemotherapy is often used in combination with other treatments, such as surgery, radiation therapy, and immunotherapy. This multimodal approach can improve outcomes by targeting cancer cells in different ways.

Future Directions

Research in chemotherapy is ongoing, with efforts to develop more targeted therapies that minimize damage to normal cells. Personalized medicine and pharmacogenomics are promising fields that aim to tailor chemotherapy regimens to individual patients based on genetic profiles.

See Also

• Oncology
• Radiation therapy
• Immunotherapy
• Targeted therapy