At what stage of cancer is chemotherapy used?
The decision to use chemotherapy may vary depending on the aggressiveness, stage and type of cancer. Usually, chemotherapy may be used for all stages in most cancer types. Chemotherapy is a type of medicine or combination of medications that is used to treat or kill cancer cells.
- Adjuvant therapy: Chemotherapy may be used after surgery to reduce the risk of cancer recurrence (coming back).
- Neoadjuvant therapy: Chemotherapy may be given before surgery to shrink the tumor. This is to help the surgery be more successful.
- Concurrent therapy: Chemotherapy may be adjusted with other therapies (radiation and chemo). It is mostly used for aggressive or stubborn cancer types.
- Palliative chemotherapy: This may also be used to relieve symptoms, improve quality of life and extend life for people with advanced cancer.
Common type of chemotherapy drugs are as follows
- Alkylating agents: These damage the DNA of cancer cells and prevent cell reproduction. These can be used in all phases of the cell lifecycle and for many types of cancers. However, they may destroy bone marrow and can sometimes lead to leukemia.
- Antimetabolites: These are used to damage cells when they’re preparing to multiply. These are often used to treat cancers such as leukemia, breast cancer, ovarian cancer and intestinal tract cancer.
- Antitumor antibiotics: This usually prevents cancer cells from growing and reproducing by changing the DNA inside them. However, high doses may damage the heart. For this reason, doses are usually limited.
- Topoisomerase inhibitors: These are used to block the function of enzymes (proteins in the cells) that are critical to cancer cell reproduction.
- Mitotic inhibitors: These are made from natural substances such as plants. They destroy cancer cells by stopping cell division. However, because they prevent enzymes from providing proteins to both cancer cells and healthy cells, they can damage cells in all phases of their lifecycle.
How is chemotherapy given?
Most chemotherapy is used as systemic therapy, which means that the drugs travel around the bloodstream and can attack cancer cells almost anywhere in the body. Chemotherapy may be given to a patient in numerous ways
- Topical: Patients may need to rub the drugs in the form of creams onto their skin.
- Oral: Patients may be asked to swallow a pill or liquid that has drugs to treat the cancer.
- Injection: Drugs are delivered with a shot directly into the muscles (hip, thigh or arm or in the fatty part of the patient’s arm, leg or stomach) just beneath the skin.
- Intravenous (IV): Chemotherapy goes directly into a vein.
- Intra-arterial (IA): Drugs go directly into the artery that is feeding the cancer through a needle or catheter (a soft, thin tube).
- Intraperitoneal (IP): Drugs are delivered into the peritoneal cavity, which contains organs such as the liver, intestines, stomach and ovaries. This is done during surgery or through a tube with a special port that is put in by the doctor.
- Intrathecal (IT) chemotherapy: Medicine is injected into the cerebrospinal fluid (CSF), which is found in the area surrounding the spinal cord and brain.
- Oral: The patient swallows a pill or liquid that has the drugs.
Why do patients have side effects with chemotherapy?
Chemotherapy usually works on cells that are actively growing and dividing. Cancer cells grow and divide quickly; hence, chemotherapy targets them quickly. However, chemotherapy can’t tell the difference between cancer cells and normal cells. Some normal cells, such as those in the hair follicles and lining of the digestive system, also grow and divide more quickly than other cells in the body. Chemotherapy can affect these cells as well. Chemotherapy can produce side effects in some, but not all, people. Different chemotherapy drugs cause different side effects. Possible side effects include
- Nausea and vomiting
- Diarrhea or constipation (often due to antinausea medication)
- Mouth sores or ulcers
- Increased risk of infection
- Increased risk of bruising
- Hair loss
- Muscle weakness
- Skin sensitivity to sunlight (specific drugs only)
- Dry or tired eyes
- Changes in appetite
- Thinking and memory changes
- Pain and sores at site of injection
- Heart damage
- Lung damage
Most are often temporary and can be treated or managed. Normal cells can usually repair the damage over time and these side effects go away once chemotherapy is completed. People may also have late effects from chemotherapy. These are side effects that are still present after six months of chemotherapy or side effects that begin years later. Late effects are not common and any risk is outweighed by the benefits of chemotherapy.