Contents
- What is cancer chemotherapy?
- How does chemotherapy work?
- Actions of Chemotherapy Drugs
- What are the different types of chemotherapy drugs?
- Alkylating Agents
- Antimetabolites
- Antimicrotubule Agents
- Antitumor Antibiotics
- Topoisomerase Inhibitors
- Small Molecule Tyrosine Kinase Inhibitors
- Miscellaneous Cancer Drugs
- What are the various chemotherapy treatment settings?
- Primary induction therapy
- Maintenance chemotherapy
- Neo-adjuvant chemotherapy
- Adjuvant chemotherapy
- Palliative chemotherapy
- How is chemotherapy given?
- Administration of Chemotherapy Drugs
- What are the negative effects of chemotherapy?
- Adverse Effects of Anti-Cancer Drugs
What is cancer chemotherapy?
Chemotherapy is the use of drugs to destroy cancer cells. It is the major tool for medical management of cancer (malignant tumors) and is not used for benign tumors. These chemicals are often highly toxic to cells, and therefore also known cytotoxic drugs. Chemotherapy is usually a systemic approach meaning that it can affect the entire body while other cancer treatments like surgery or radiation therapy are a local approach.
How does chemotherapy work?
Actions of Chemotherapy Drugs
Cancer transforms normal cells into malignant cells that then undergo abnormal division. The regulating mechanisms to control cell growth and differentiation is essentially hampered or lost and there is uncontrolled growth. Chemotherapy destroys the cancer cells by different mechanisms. Some chemotherapy drugs promote cancer cell destruction by interfering with cellular function and multiplication. Many chemotherapeutic drugs inhibit DNA synthesis while some drugs damage the DNA or cell, leading to cell death. Chemotherapy cannot specifically differentiate cancer cells and the normal healthy cells. This can lead to damage in several normal cells in the process resulting in significant adverse effects.
What are the different types of chemotherapy drugs?
Alkylating Agents
Alkylating agents inhibit cell function and division by reacting with DNA and alkylating it. This type of drugs include cyclophosphamide, mephalan, nitrosureas like carmustine and platinum compounds like cisplatin.
Antimetabolites
These resemble the normal substance within the cell and affect cancer cells by interfering with its division. Examples include fluorouracil and methotrexate.
Antimicrotubule Agents
Vinca alkaloids like vincristine are drugs that are derived from the plant Vinca rosea and taxanes like paclitaxel obtained from yews, inhibit the cell division by inhibiting the microtubule.
Antitumor Antibiotics
These are anticancer drugs derived from fungi like anthracyclins (doxorubicin).
Topoisomerase Inhibitors
It blocks the action of topoisomerase I and II, enzymes that promote unbinding of double helical DNA, which is essential for cell replication. This group includes drugs like irinotecan and topotecan.
Small Molecule Tyrosine Kinase Inhibitors
This is a group of drugs that are targeted drugs which inhibit certain enzymes present in pathways involving cancer cells. Unlike the conventional chemotherapy drugs, these are not cytotoxic. Drugs in this group include imatinib, sorafenib and sunitinib.
Miscellaneous Cancer Drugs
Drugs targeting proteasome like bortezomib, histone deacetylase inhibitors like vorinostat, thalidomide, and L-asparaginase are some of the other chemotherapeutic agents which are approved for treating cancer.
What are the various chemotherapy treatment settings?
Primary induction therapy
Chemotherapy administered as the first treatment for patients with advanced cancer in the absence of any alternative treatment options is referred to as primary induction therapy. In advanced cancer, when multiple drugs are useful against cancer, the most effective drugs that are considered to be standard drugs are referred as first-line drug. Drugs used after failure of a first-line agent are known as a second-line drug.
Maintenance chemotherapy
Following induction, the chemotherapy may be continued at lower doses than required for induction therapy until complete remission or disease progression.
Neo-adjuvant chemotherapy
Neo-adjuvant chemotherapy is the use of chemotherapy before local therapy like surgery or radiation therapy in patients who have cancer that has not spread. Neo-adjuvant chemotherapy is expected to shrink the tumor and increase the success rate of the planned local treatment that follows it.
Adjuvant chemotherapy
Chemotherapy given after surgery or radiotherapy to destroy leftover cancerous cells is referred as adjuvant chemotherapy.
Palliative chemotherapy
Palliative chemotherapy is aimed to prolong life and provide improvement in quality of life without any expectation of cure of the cancer.
How is chemotherapy given?
Administration of Chemotherapy Drugs
Chemotherapy drugs are usually administered intravenously, orally or locally, although other routes may be used for certain drugs in certain cancers. Chemotherapy drugs may be given as a single drug (monotherapy) or multiple drugs (combination therapy). Sometimes chemotherapy may be combined with surgery and radiotherapy. The dosage or treatment schedule can be daily or in weekly cycles or monthly cycles depending upon the type of drug, type of treatment, type of cancer, stage and site of cancer, extent of spread, and overall health of the patient.
What are the negative effects of chemotherapy?
Adverse Effects of Anti-Cancer Drugs
In the short term, the adverse effects may include :
- nausea
- vomiting
- fatigue
- hair loss
- dermatitis
- anemia
- leucopenia (low white blood count)
- thrombocytopenia (low platelet count)
- mouth ulcers
- stomach and intestinal ulcers
- pain
- diarrhea
- constipation
- neuropathy
- sedation
- toxicity to kidney and liver
- hemorrhage from bladder (cystitis)
Most of the side-effects disappear after completion of treatment, but some produce long-term or delayed effects. Infertility and a risk of leukemia are some of the delayed side effects.
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