Chemotherapy is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents) as part of a standardized chemotherapy regimen. The term chemotherapy refers to the drugs that prevent cancer cells from dividing and growing. It does this by killing the dividing cells. Chemotherapy may be given with a curative intent (which almost always involves combinations of drugs), or it may aim to prolong life or to reduce symptoms (palliative chemotherapy). Chemotherapy is one of the major categories of the medical discipline specifically devoted to pharmacotherapy for cancer, which is called medical oncology.
Types of Chemotherapy
There are many chemotherapy drugs that are grouped into classes depending on how they work. Combining chemotherapy drugs from different classes can make the treatment work better because the different drugs attack cancer cells at different points in their growth cycle. It may also prevent resistance and help lower the chance of cancer coming back (recurrence). Some types of chemotherapy include:
- DNA-damaging agents are also called alkylating agents. They stop cells from dividing by changing the cell’s DNA so it can’t be copied. Because cancer cells grow and divide quickly, they end up dying because they don’t have time to repair the damaged DNA.
- Antimetabolites act like the building blocks of DNA or RNA that cancer cells need to grow and survive. When a cancer cell uses the antimetabolite chemotherapy drug instead of their own substances, the DNA is damaged and the cell dies.
- Antimitotics block the process of cell division called mitosis so cells can’t divide and multiply.
- Antitumour antibiotics bind to DNA so it can’t work properly. This causes the cell to die. These drugs are different than antibiotics used to treat infection.
- DNA-repair enzyme inhibitors prevent the normal repair of DNA damage inside the cell. These chemotherapy drugs attack the enzymes that normally repair damage to DNA. If a cancer cell can’t repair damage to DNA, it dies.
How is Chemotherapy Given
- Intravenous (IV) chemotherapy – Many drugs require injection directly into a vein. This is called intravenous or IV chemotherapy. Treatment takes a few minutes to a few hours. Some IV drugs work better if you get them over a few days or weeks. You take them through a small pump you wear or carry. This is called continuous infusion chemotherapy.
- Oral chemotherapy – You can take some drugs by mouth. They can be in a pill, capsule, or liquid. This means that you may be able to pick up your medication at the pharmacy and take it at home. Oral treatment for cancer is now more common, since many drugs used for targeted therapy work this way. Some of these drugs are given daily, and others are given less often. For example, a drug may be given daily for 4 weeks followed by a 2-week break.
- Injected chemotherapy – This is when you receive chemotherapy as a shot. In some cases, the shot is given in a muscle, while other drugs are injected under the skin. This could be in the arm, leg, or abdomen.
- Chemotherapy into an artery – An artery is a blood vessel that carries blood from your heart to another part of your body. Sometimes chemotherapy is injected into an artery that goes directly to the cancer. This is called intra-arterial or IA chemotherapy.
- Chemotherapy into the peritoneum or abdomen – For some cancers, medication might be placed directly in your abdomen. Abdomen is the medical term for your belly. This type of treatment works for cancers involving the peritoneum. The peritoneum covers the surface of the inside of the abdomen and surrounds the intestines, liver, and stomach. Ovarian cancer is one type of cancer that frequently spreads to the peritoneum.
- Topical chemotherapy – You can take some types of chemotherapy in a cream you put on your skin. You get your medication at the pharmacy and take it at home.
Other Drug Treatments for Cancer
The traditional drugs used for chemotherapy are an important part of treatment for many cancers. The drugs affect both cancer cells and healthy cells. But scientists have designed newer drugs that work more specifically to treat cancer. These treatments cause different side effects.
Doctors may use these newer cancer drugs as the only drug treatment. But they are usually added to traditional chemotherapy. These types of treatment include:
- Hormone therapy – These treatments change the amount of hormones in your body. Hormones are chemicals your body makes naturally. They help control the activity of certain cells or organs. Doctors use hormone therapy because hormone levels control several types of cancers. This includes some breast and prostate cancers.
- Targeted therapy – These treatments target and disable genes or proteins found in cancer cells that the cancer cells need to grow.
- Immunotherapy – This type of treatment helps your body’s natural defenses fight the cancer. This type of treatment may be used for some types of cancer now and will play an increasingly important role in cancer treatment in the future.
Other ways that chemotherapy is given include
- by mouth, such as with pills or capsules (oral chemotherapy)
- into the cerebrospinal fluid (CSF) surrounding the spinal cord (intrathecal chemotherapy)
- into the CSF within the brain (intraventricular chemotherapy)
- into an artery (intra-arterial chemotherapy)
- into a body cavity, such as the abdomen or chest (intracavitary chemotherapy)
- into a muscle (intramuscular chemotherapy)
- directly into a tumour (intralesional chemotherapy)
- using a cream or ointment on the skin (topical chemotherapy)
Goals of Chemotherapy
Chemotherapy in the treatment of cancer can have different goals. This is why we differentiate between the following types of chemotherapy:
- Curative chemotherapy – Curative chemotherapy aims to eliminate all cancer cells from the body and to achieve a permanent cure.
- Adjuvant chemotherapy – Adjuvant chemotherapy aims at cancer cells that might be left in the body after surgery, but that cannot be detected. This kind of supportive therapy aims to prevent recurrences.
- Neoadjuvant chemotherapy – Neoadjuvant chemotherapy is done before surgery. Some tumors are too big to be directly operated on. Chemotherapy can often shrink the tumor, making it possible to remove it surgically. It may also aim to allow less invasive surgery.
- Palliative chemotherapy – Chemotherapy is called palliative when it is no longer possible to remove all tumor cells. Chemotherapy can then help to relieve certain symptoms, to slow down the progress of the disease or to stop it temporarily, and to avoid complications.
How Chemotherapy is Done
Types of applications
- In chemotherapy, the body is given medications. This is usually done with an infusion into a vein, but some medications can also be taken as tablets. There are many different cytostatics, which are often given in combination with one another. Because drugs that are given this way travel in the bloodstream, they usually act in all parts of the body. So they can also get to cancer cells that are not detected in examinations, and that can therefore not be targeted with surgery or radiation. Experts also call this kind of therapy systemic treatment.
- In rare cases, it is also possible to use local chemotherapy. Then the medications are not given over the bloodstream, but are injected directly into the affected body region, for example the spinal canal. Then the drugs only reach connected areas, such as the brain or the membranes lining the brain and spinal cord. Basal cell cancer, a type of skin cancer, is sometimes treated with chemotherapy applied as a cream or an ointment, which only act locally.
- Chemotherapy is often combined with radiotherapy – this is then called radiochemotherapy. Radiotherapy can be done at the same time or after chemotherapy. Some chemotherapeutical drugs only have an effect when they are subjected to radiotherapy. In this case, chemotherapy only acts locally in the places where radiation was applied.
- People who get cytostatics over a longer period of time can sometimes get these drugs through a device called a port. A port consists of a small container, which is inserted under the skin in a minor operation, and connects to a large vein with a thin tube. It can remain in the body for as long as treatment lasts. This has the advantage that infusions can be connected to the port and it is not necessary to look for a vein and puncture it for each treatment.
In chemotherapy, cancer is treated with cytostatics at specific intervals. This is also referred to as treatment cycles or treatment schedules. Various factors influence the number of cycles and the intervals between the individual treatments:
how long the effect of the administered drug lasts,
how much time the body needs to recover, and
the overall length of treatment, for example.
Treatment schedules are tested in studies, which allows them to be optimized over time. How exactly a treatment is done not only depends on research results, however but also on personal wishes and the state of health of the individual person. If chemotherapy is causing severe adverse effects, for example, it can make sense to deviate from the commonly used therapy schedule.
Different tests like blood tests, tissue samples and imaging techniques like computed tomography, for example, help find out whether a tumor responds to the chemotherapy. If this is not the case, other substances can be used for treatment, or treatment can be stopped.
|Breast cancer||Cyclophosphamide, methotrexate, 5-fluorouracil, vinorelbine||CMF|
|Hodgkin’s lymphoma||Docetaxel, doxorubicin, cyclophosphamide||TAC|
|Doxorubicin, bleomycin, vinblastine, dacarbazine||ABVD|
|Mustine, vincristine, procarbazine, prednisolone||MOPP|
|Non-Hodgkin’s lymphoma||Cyclophosphamide, doxorubicin, vincristine, prednisolone||CHOP|
|Germ cell tumor||Bleomycin, etoposide, cisplatin||BEP|
|Stomach cancer||Epirubicin, cisplatin, 5-fluorouracil||ECF|
|Epirubicin, cisplatin, capecitabine||ECX|
|Bladder cancer||Methotrexate, vincristine, doxorubicin, cisplatin||MVAC|
|Lung cancer||Cyclophosphamide, doxorubicin, vincristine, vinorelbine||CAV|
|Colorectal cancer||5-fluorouracil, folinic acid, oxaliplatin||FOLFOX|
There are a number of strategies in the administration of chemotherapeutic drugs used today. Chemotherapy may be given with a curative intent or it may aim to prolong life or to palliate symptoms[rx].
- Induction chemotherapy is the first line treatment of cancer with a chemotherapeutic drug. This type of chemotherapy is used for curative intent.[rx]
- Combined modality chemotherapy is the use of drugs with other cancer treatments, such as surgery, radiation therapy, or hyperthermia therapy.
- Consolidation chemotherapy is given after remission in order to prolong the overall disease-free time and improve overall survival. The drug that is administered is the same as the drug that achieved remission.[rx]
- Intensification chemotherapy is identical to consolidation chemotherapy but a different drug than the induction chemotherapy is used.[rx]
- Combination chemotherapy involves treating a person with a number of different drugs simultaneously. The drugs differ in their mechanism and side-effects. The biggest advantage is minimising the chances of resistance developing to any one agent. Also, the drugs can often be used at lower doses, reducing toxicity.[rx][rx][rx]
- Neoadjuvant chemotherapy is given prior to a local treatment such as surgery, and is designed to shrink the primary tumor.[rx]It is also given to cancers with a high risk of micrometastatic disease.[rx]
- Adjuvant chemotherapy is given after a local treatment (radiotherapy or surgery). It can be used when there is little evidence of cancer present, but there is risk of recurrence.[rx] It is also useful in killing any cancerous cells that have spread to other parts of the body. These micrometastases can be treated with adjuvant chemotherapy and can reduce relapse rates caused by these disseminated cells.[rx]
- Maintenance chemotherapy is a repeated low-dose treatment to prolong remission.[rx][rx]
- Salvage chemotherapy or palliative chemotherapy is given without curative intent, but simply to decrease tumor load and increase life expectancy. For these regimens, in general, a better toxicity profile is expected.[rx]
All chemotherapy regimens require that the recipient be capable of undergoing the treatment. Performance status is often used as a measure to determine whether a person can receive chemotherapy, or whether dose reduction is required. Because only a fraction of the cells in a tumor die with each treatment (fractional kill), repeated doses must be administered to continue to reduce the size of the tumor.[rx]Current chemotherapy regimens apply drug treatment in cycles, with the frequency and duration of treatments limited by toxicity.[rx]
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