chemotherapy
Meaning of chemotherapy: Given in cycles rather than continuously, so the healthy tissues that renew fastest have time to recover between rounds.
Definition of chemotherapy
Chemotherapy is treatment with drugs that damage cells as they divide, used mainly against cancer because cancer cells divide more often than most healthy ones. The drugs travel in the bloodstream and reach tissue throughout the body, which is why they also affect normal tissues that renew quickly, such as bone marrow, the lining of the gut and hair follicles.
What is chemotherapy given for?
The same drugs serve several distinct purposes, and the name of the purpose says more about the plan than the name of the drug does.
| Purpose | What it means |
|---|---|
| Neoadjuvant | Given before surgery or radiation to shrink a tumor and make removal easier |
| Adjuvant | Given after the visible tumor is removed, aimed at cells that may have spread but cannot be seen |
| Primary or definitive | The main treatment, used for cancers such as leukemias and lymphomas that are not localized to one site |
| Palliative | Given to control a cancer and relieve the symptoms it causes rather than to remove it |
It is frequently combined with radiation therapy, with surgery, or with newer classes of cancer drug, and several chemotherapy agents are usually given together because cancers respond less predictably to a single one.
Why does it come in cycles?
A course is built from a treatment period followed by a gap, repeated a set number of times. The gap exists because bone marrow, gut lining and hair follicles renew constantly and take the same hit as the tumor. Given time, those tissues recover; a tumor recovers less completely, so the deficit accumulates across cycles. Blood counts fall to their lowest point some days after a dose and then rebuild, which is the rhythm the schedule is designed around. Delivery is not always through a vein either: some agents are swallowed, and others are placed directly into a body cavity or an artery supplying the tumor, as in regional chemotherapy.
How is it different from targeted therapy and immunotherapy?
Chemotherapy is not a synonym for cancer drug treatment. It works on cell division itself, so it hits any rapidly dividing cell it reaches. Targeted therapy instead blocks a specific molecule that a particular cancer depends on, which is why tumor testing decides whether it can be used at all. Immunotherapy does not attack the cancer directly but removes the brakes that stop immune cells from doing so. The three have different patterns of effect, and a modern regimen may combine them, but they are separate categories rather than variations on one idea.
Used in a sentence
The patient began a course of chemotherapy following surgical removal of the tumor.
Good to know
Chemotherapy affects rapidly dividing cells generally, not only cancer cells, which is why effects such as hair loss and changes in blood counts commonly accompany treatment even though the drugs are aimed at the cancer.
Word origin
Where “chemotherapy” comes from
Formed from chemo-, referring to chemical substances, and therapy, from Greek therapeia, meaning treatment or healing.