Chemotherapy is a type of cancer treatment that uses drugs to kill cancer cells. Cancer cells grow and divide faster than normal cells, so chemotherapy targets them more effectively. Chemotherapy can be used to cure cancer, prevent it from coming back, slow its growth, or relieve symptoms caused by tumors.


Types of Chemotherapy

There are many different types of chemotherapy drugs available. They can be classified based on their chemical structure, their mechanism of action, their effect on the cell cycle, or their role in the treatment plan. Some common types of chemotherapy drugs are:

Alkylating agents: These drugs damage the DNA of cancer cells and prevent them from reproducing. Examples are cyclophosphamide, cisplatin, and temozolomide.

– Antimetabolites: These drugs interfere with the synthesis of DNA or RNA, which are essential for cell growth and division. Examples are methotrexate, fluorouracil, and gemcitabine.

Antitumor antibiotics: These drugs block the action of enzymes that are involved in DNA replication or repair. Examples are doxorubicin, bleomycin, and mitomycin.

Plant alkaloids: These drugs affect the structure or function of microtubules, which are important for cell division. Examples are vincristine, paclitaxel, and vinorelbine.

Corticosteroids: These drugs reduce inflammation and suppress the immune system. They are often used to treat lymphoma and leukemia, or to reduce side effects of other chemotherapy drugs. Examples are prednisone, dexamethasone, and methylprednisolone.

Chemotherapy drugs can be given in different ways, such as:

Intravenous (IV): The drug is injected into a vein through a needle or a catheter.

Oral: The drug is taken by mouth as a pill or a liquid.

Intramuscular (IM): The drug is injected into a muscle.

Subcutaneous (SC): The drug is injected under the skin.

Intrathecal (IT): The drug is injected into the cerebrospinal fluid that surrounds the brain and spinal cord.

Topical: The drug is applied to the skin as a cream or a lotion.

The choice of chemotherapy drugs and the way they are given depend on many factors, such as:

– The type and stage of cancer

– The goal of treatment

– The patient’s age, weight, and general health

– The patient’s preferences and values

– The potential benefits and risks of each option


Principles of Chemotherapy


Chemotherapy is a cancer treatment that involves the administration of chemical drugs to kill cancer cells. It is usually given in cycles, which are periods of treatment followed by periods of rest. This allows the body to recover from the effects of the drugs and also increases the chance of killing more cancer cells. Each cycle may last from a few days to several weeks.

Chemotherapeutic drugs act on fast-dividing cells by arresting the mitotic stages of the cell cycle. Cancer cells are usually more sensitive to these drugs than normal cells because they divide more rapidly and have less ability to repair DNA damage. However, some normal cells, such as those in the bone marrow, hair follicles, gastrointestinal tract and reproductive organs, also divide quickly and can be affected by chemotherapy. This causes some of the common side effects of chemotherapy, such as anemia, hair loss, nausea, vomiting and infertility.

The aim of chemotherapy is to cure cancer where possible and palliate where cure is impossible. The effective use of chemotherapy needs a deep understanding of the principles of tumor biology, pharmacology and pharmacokinetics of the drugs, drug resistance mechanisms, drug interactions and toxicity management¹.

According to the log-kill principle, chemotherapeutic agents only kill a constant fraction of cells rather than a specific number of cells. A consequence of this hypothesis is that the chemotherapy dose should not be reduced in the case of a small tumor burden.


Various ways of chemotherapy administration

The timing of administration: Chemotherapy can be given before surgery or radiation therapy (neoadjuvant), after surgery or radiation therapy (adjuvant), along with surgery or radiation therapy (concurrent) or alone as the primary treatment (induction).

The combination of drugs: Chemotherapy can be given as a single drug (monotherapy) or as a combination of two or more drugs (polytherapy). Combination chemotherapy is usually more effective than monotherapy because it can target different aspects of cancer cell growth and survival and reduce the risk of drug resistance.

The mechanism of action: Chemotherapy drugs can be grouped into different classes based on how they interfere with DNA synthesis or function, such as alkylating agents, antimetabolites, antitumor antibiotics, topoisomerase inhibitors, mitotic inhibitors and platinum compounds. Some newer classes of chemotherapy drugs target specific molecules or pathways that are involved in cancer cell growth or survival, such as tyrosine kinase inhibitors, monoclonal antibodies, immunomodulators and proteasome inhibitors.


Use Case Scenarios


Chemotherapy can be used in different scenarios depending on the type, stage and location of cancer, the patient’s general health and preferences and the availability and cost of other treatments. Some examples of use case scenarios are:

– Chemotherapy can be used as a curative treatment for some types of cancers that are highly responsive to chemotherapy, such as acute leukemias, lymphomas, testicular cancers and some childhood cancers.

– Chemotherapy can be used as a neoadjuvant treatment to shrink tumors before surgery or radiation therapy, which can make them easier to remove or treat and increase the chance of cure. For example, chemotherapy is often used before surgery for breast cancer, colorectal cancer and osteosarcoma.

– Chemotherapy can be used as an adjuvant treatment to eliminate any remaining cancer cells after surgery or radiation therapy, which can reduce the risk of recurrence or metastasis. For example, chemotherapy is often used after surgery for breast cancer, colorectal cancer and lung cancer.

– Chemotherapy can be used as a concurrent treatment with radiation therapy to enhance the effect of radiation on killing cancer cells. For example, chemotherapy is often used with radiation therapy for head and neck cancers, cervical cancers and esophageal cancers.

– Chemotherapy can be used as a palliative treatment to relieve symptoms and improve quality of life for patients with advanced or metastatic cancers that cannot be cured by other treatments. For example, chemotherapy can be used to control pain, bleeding, obstruction or compression caused by tumors in various organs.


Benefits and Challenges


Chemotherapy has many benefits for cancer patients, such as:

– It can cure some types of cancers that were previously considered incurable.

– It can increase the chance of cure or prolong survival for many types of cancers when used with other treatments.

– It can improve the symptoms and quality of life for patients with advanced or metastatic cancers.

– It can be given in different ways and schedules to suit the patient’s needs and preferences.

– It can be combined with other treatments, such as surgery, radiation therapy, targeted therapy, immunotherapy and hormone therapy, to achieve better outcomes.

However, chemotherapy also has some challenges, such as:

– It can cause many side effects that can affect the patient’s physical and mental health, such as fatigue, nausea, vomiting, diarrhea, constipation, mouth sores, hair loss, skin changes, infections, bleeding, nerve damage, kidney damage, heart damage and infertility.

– It can be expensive and require frequent visits to the hospital or clinic for administration and monitoring.

– It can interact with other drugs or supplements that the patient may be taking for other conditions or for supportive care.

– It can lose its effectiveness over time due to the development of drug resistance by cancer cells.

– It can increase the risk of developing secondary cancers or other diseases later in life due to the damage to normal cells and DNA.



Chemotherapy is a powerful and versatile treatment for cancer that can cure, control or palliate many types of cancers. However, it also has some limitations and drawbacks that need to be considered and managed carefully. Therefore, it is important for patients to consult with their oncologists and understand the goals, benefits, risks and alternatives of chemotherapy before starting the treatment. It is also important for patients to follow the instructions and advice of their oncologists and health care team during and after the treatment to minimize the side effects and maximize the outcomes of chemotherapy.


## References

(1) Cancer Chemotherapy – StatPearls – NCBI Bookshelf.

(2) Chemotherapy – History, Principles, Aim, Types, Side Effcts, Pros & Cons.


(4) Principles of chemotherapy – Lundqvist – 2015 – International Journal

(5) Principles of chemotherapy | Oxford Textbook of Oncology | Oxford Academic.

(6) CHAPTER 27: Principles of Chemotherapy | Obgyn Key.

(7) Principles of Chemotherapy | Epomedicine.