Cancer Treatment Glossary

A

Ablation

A procedure that destroys tumour tissue using heat (radiofrequency ablation), cold (cryoablation), or other energy sources. Often used for small liver or kidney tumours when surgery is not an option.

Adenocarcinoma

A cancer that starts in glandular cells — the cells that line organs and produce mucus or other fluids. This is one of the most common types and can occur in the lungs, colon, pancreas, breast, and other organs.

Adjuvant therapy

Treatment given after the primary treatment (usually surgery) to reduce the risk of cancer returning. Common adjuvant therapies include chemotherapy, radiation, hormone therapy, and targeted therapy.

Anaplastic

Describes cancer cells that look very abnormal under a microscope and tend to grow and spread quickly. Anaplastic tumours are generally high-grade and more aggressive.

Angiogenesis

The process by which tumours stimulate the growth of new blood vessels to supply themselves with oxygen and nutrients. Some cancer drugs work by blocking angiogenesis, cutting off the tumour’s blood supply.

Antiemetic

A medication that prevents or reduces nausea and vomiting. Antiemetics are commonly prescribed during chemotherapy to manage one of its most common side effects.

Apoptosis

Programmed cell death — the body’s natural process of eliminating old or damaged cells. Cancer cells often find ways to avoid apoptosis, which allows them to keep growing.

B

Benign

A growth or tumour that is not cancer. Benign tumours do not invade nearby tissue or spread to other parts of the body. They may still need treatment if they press on vital structures or cause symptoms.

Biomarker

A measurable substance in the body — such as a protein, gene, or molecule — that can indicate the presence of cancer, predict how it will behave, or help guide treatment decisions. Examples include HER2, PD-L1, and BRCA mutations.

Biopsy

A procedure in which a small sample of tissue is removed from the body and examined under a microscope to determine whether cancer is present. Types include needle biopsy, surgical biopsy, and endoscopic biopsy.

Bone marrow

The soft, spongy tissue inside bones where blood cells are made. Bone marrow can be affected by cancers like leukaemia and can also be damaged by certain chemotherapy drugs.

Brachytherapy

A form of radiation therapy where a sealed radiation source is placed inside or next to the area requiring treatment. Commonly used for uterine and prostate cancers.

BRCA (BRCA1 and BRCA2)

Genes that normally help repair damaged DNA. Inherited mutations in BRCA1 or BRCA2 significantly increase the risk of breast cancer and ovarian cancer. Genetic testing can identify carriers.

C

CAR-T cell therapy

A type of immunotherapy in which a patient’s own T cells (a type of immune cell) are collected, genetically modified in a laboratory to recognise cancer cells, and then infused back into the patient. Currently used mainly for certain blood cancers including some forms of leukaemia.

Carcinogen

Any substance or exposure that can cause cancer by damaging the DNA in cells. Known carcinogens include tobacco smoke, ultraviolet radiation, asbestos, and certain chemicals.

Carcinoma

A cancer that begins in the skin or in tissues that line or cover internal organs (epithelial tissue). Carcinomas account for the majority of all cancers and include subtypes such as adenocarcinoma and squamous cell carcinoma.

Checkpoint inhibitor

A type of immunotherapy drug that blocks proteins used by cancer cells to hide from the immune system. By releasing these “brakes” (checkpoints), the immune system can recognise and attack the cancer. Examples include pembrolizumab and nivolumab.

Chemotherapy

Treatment that uses drugs to kill rapidly dividing cells, including cancer cells. Chemotherapy can be given intravenously or orally, and is used to cure cancer, shrink tumours before surgery, or reduce the risk of recurrence after surgery.

Clinical trial

A carefully designed research study that tests new treatments, drugs, or approaches in human volunteers. Clinical trials are how medical advances are proven safe and effective. They go through phases I–IV, with each phase answering different questions about the treatment.

Complete response (CR)

When all signs of cancer disappear after treatment. Also called complete remission. This does not always mean the cancer is cured, which is why follow-up monitoring is important.

CT scan (computed tomography)

An imaging test that uses X-rays taken from many angles to create detailed cross-sectional pictures of the inside of the body. CT scans are widely used to detect cancer, determine its size and location, check for spread, and monitor response to treatment.

Cytology

The study of cells under a microscope. In cancer care, cytology examines cells collected from body fluids or tissue samples to check for abnormalities. A Pap smear is a common cytology test used in cervical cancer screening.

D

Differentiation

How much cancer cells resemble normal cells when viewed under a microscope. Well-differentiated cancer cells look more like normal cells and tend to grow slowly. Poorly differentiated or undifferentiated cells look very abnormal and tend to be more aggressive.

Distant metastasis

Cancer that has spread from the primary tumour to organs or tissues far away in the body. This is also referred to as stage IV disease for most cancer types.

Dose-dense chemotherapy

A chemotherapy schedule in which treatments are given more frequently than the standard schedule (for example, every two weeks instead of every three) with the support of growth factors to help the bone marrow recover.

Dysplasia

Abnormal changes in cells that may be a precancerous condition. Dysplasia is not cancer, but if left untreated, it can sometimes progress to cancer over time.

E

EGFR (epidermal growth factor receptor)

A protein found on the surface of cells that helps them grow and divide. Some cancers, particularly lung cancer, have mutations in EGFR that make cells grow too quickly. Targeted drugs called EGFR inhibitors can block this signal.

Excision

The surgical removal of tissue, a tumour, or an organ. A wide excision removes the tumour along with a margin of normal tissue around it to help ensure all cancer cells are removed.

External beam radiation

The most common type of radiation therapy, in which a machine outside the body directs high-energy beams at the cancer. Treatments are typically given daily over several weeks.

F

FIGO staging

A staging system developed by the International Federation of Gynecology and Obstetrics, used specifically for gynaecological cancers such as ovarian, uterine, and cervical cancers. It uses stages I–IV, with sub-stages to describe the extent of disease.

Fine needle aspiration (FNA)

A type of biopsy that uses a very thin needle to withdraw a small sample of cells from a lump or mass. It is less invasive than a surgical biopsy and is often used as a first step in evaluating a suspicious finding.

First-line therapy

The first treatment given for a cancer. If first-line therapy does not work or stops working, second-line therapy (and sometimes third-line) may be tried.

G

Grade

A measure of how abnormal cancer cells look under a microscope, which indicates how quickly they are likely to grow and spread. Low-grade (grade 1) cancers look more like normal cells and tend to grow slowly. High-grade (grade 3) cancers look very abnormal and tend to be aggressive.

Growth factor

A naturally occurring substance, usually a protein, that stimulates cell growth and division. Some cancer treatments block growth factors to slow or stop tumour growth. Colony-stimulating factors (like G-CSF) are growth factors given to patients to help bone marrow recover after chemotherapy.

H

HER2 (human epidermal growth factor receptor 2)

A protein that promotes cell growth. Some cancers, especially breast cancer and stomach cancer, have too many copies of the HER2 gene (HER2-positive), which makes them grow faster. Targeted therapies like trastuzumab are designed to block HER2.

Hormone receptor (HR)

A protein on the surface of cells that binds to specific hormones. In breast cancer and uterine cancer, tumours that are hormone receptor–positive (HR+) grow in response to oestrogen and/or progesterone and can be treated with hormone-blocking therapies.

Hospice

A type of care focused on comfort, pain management, and quality of life for patients with a terminal illness, typically when curative treatment is no longer being pursued. Hospice care can be provided at home, in a hospice facility, or in a hospital.

I

Immunotherapy

A broad category of cancer treatment that harnesses the body’s own immune system to fight cancer. Types include checkpoint inhibitors, CAR-T cell therapy, and cancer vaccines. Immunotherapy has transformed the treatment of cancers such as lung cancer and melanoma.

Incidence

The number of new cases of a disease diagnosed in a specific population during a specific time period. Cancer incidence rates help researchers track trends and identify risk factors.

In situ

A term meaning “in place.” Carcinoma in situ describes cancer cells that are found only in the layer of tissue where they first formed and have not spread to nearby tissue. It is the earliest stage of cancer (stage 0) and is often highly curable.

Infusion

A method of delivering fluids, drugs, or blood products directly into a vein over a period of time. Many chemotherapy drugs and immunotherapy agents are given by intravenous (IV) infusion.

J

Jaundice

A yellowing of the skin and whites of the eyes caused by a build-up of bilirubin in the blood. In cancer patients, jaundice can be a symptom of liver cancer or pancreatic cancer if a tumour blocks the bile duct.

K

Karnofsky performance score (KPS)

A scoring system (0–100) that measures a patient’s ability to perform ordinary daily tasks. A score of 100 means no evidence of disease and full ability to function; lower scores indicate increasing levels of disability. Doctors use KPS to help determine whether a patient can tolerate certain treatments.

L

Lesion

An area of abnormal tissue in the body. A lesion may be benign or malignant. Further testing, often including a biopsy, is usually needed to determine what a lesion is.

Leukaemia

A group of cancers that start in the bone marrow and result in high numbers of abnormal white blood cells. Leukaemia can be acute (fast-growing) or chronic (slow-growing), and is classified further by the type of white blood cell affected.

Lymph node

Small, bean-shaped structures throughout the body that filter lymph fluid and help fight infection. Cancer cells can spread to nearby lymph nodes, and checking lymph nodes is an important part of cancer staging.

Lymphoedema

Swelling, usually in an arm or leg, caused by a blockage in the lymphatic system. It can develop after surgery or radiation that damages or removes lymph nodes, and is a common long-term side effect of treatment for breast cancer.

M

Malignant

Cancerous. A malignant tumour can invade surrounding tissues and spread (metastasise) to distant parts of the body. This is the key distinction between malignant and benign growths.

Margin

The edge of the tissue removed during surgery. A “negative” or “clear” margin means no cancer cells were found at the edge, suggesting the entire tumour was removed. A “positive” margin means cancer cells are present at the edge, which may require additional treatment.

Metastasis

The process by which cancer spreads from the place where it first formed (primary site) to other parts of the body. Cancer cells can metastasise through the blood or lymphatic system. A cancer that has spread is called metastatic cancer.

Molecular profiling

Testing a tumour’s DNA, RNA, or proteins to identify specific genetic changes (mutations, amplifications, or fusions) that are driving the cancer’s growth. The results help oncologists select targeted therapies or immunotherapies that are most likely to work for that particular tumour.

MRI (magnetic resonance imaging)

An imaging technique that uses powerful magnets and radio waves to create detailed pictures of organs and tissues in the body. MRI does not use radiation and is particularly useful for imaging the brain, spinal cord, and soft tissues.

Mucositis

Painful inflammation and ulcers in the lining of the mouth, throat, or digestive tract. It is a common side effect of chemotherapy and head-and-neck radiation therapy.

Multidisciplinary team (MDT)

A group of healthcare professionals from different specialities who work together to plan and deliver a patient’s cancer treatment. An MDT typically includes surgeons, medical oncologists, radiation oncologists, pathologists, radiologists, and specialist nurses.

N

Neoadjuvant therapy

Treatment given before the primary treatment (usually surgery) to shrink a tumour and make it easier to remove. Common neoadjuvant approaches include chemotherapy, radiation, or a combination of both.

Neoplasm

An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should. Neoplasms can be benign (not cancer) or malignant (cancer).

Neutropenia

An abnormally low level of neutrophils, a type of white blood cell essential for fighting infection. Neutropenia is a common and potentially serious side effect of chemotherapy because these drugs can suppress bone marrow function. Patients with neutropenia are at increased risk for infections.

Nodule

A small, rounded lump found in tissue. Lung nodules, for example, are commonly detected on CT scans. Most nodules are benign, but some require monitoring or biopsy to rule out cancer.

O

Oncologist

A doctor who specialises in diagnosing and treating cancer. There are several types: medical oncologists (drug treatments), surgical oncologists (surgery), and radiation oncologists (radiation therapy). Finding the right oncologist is an important first step after diagnosis.

Oncology

The branch of medicine devoted to the study, diagnosis, treatment, and prevention of cancer.

Overall survival (OS)

The length of time from the start of treatment (or from diagnosis) that a patient is still alive. Overall survival is one of the most important measures used to evaluate how well a cancer treatment works.

P

Palliative care

Specialised medical care focused on relieving symptoms, pain, and stress of a serious illness. Palliative care can be provided at any stage of cancer — alongside curative treatment or on its own — and aims to improve quality of life for both the patient and their family.

Pathology

The medical speciality that examines tissue samples, blood, and other body fluids to diagnose disease. After a biopsy or surgery, a pathologist examines the tissue under a microscope and produces a pathology report that describes the type, grade, and characteristics of the cancer.

PD-L1 (programmed death-ligand 1)

A protein that some cancer cells produce in large amounts to hide from the immune system. Tumours with high PD-L1 levels may respond well to checkpoint inhibitor immunotherapy drugs that block the PD-1/PD-L1 pathway.

PET scan (positron emission tomography)

An imaging test in which a small amount of radioactive sugar is injected into the body. Cancer cells, which use more sugar than normal cells, absorb more of the tracer and show up as bright spots on the scan. PET scans are often combined with CT scans (PET/CT) to provide both functional and structural information.

Platelet

A type of blood cell that helps the body form clots to stop bleeding. Chemotherapy can lower platelet counts (thrombocytopenia), increasing the risk of bleeding and bruising.

Port (port-a-cath)

A small medical device implanted under the skin, usually in the chest, that connects to a large vein. It provides easy and reliable access for delivering chemotherapy, drawing blood, and giving IV fluids without repeated needle sticks.

Prognosis

The likely course and outcome of a disease. A prognosis is based on factors including the cancer type, stage, grade, patient’s overall health, and response to treatment. Prognosis is typically described using survival statistics, but each patient’s experience is individual.

Progression-free survival (PFS)

The length of time during and after treatment that a patient lives without the cancer growing or spreading. PFS is a common endpoint in clinical trials.

R

Radiation therapy (radiotherapy)

Treatment that uses high-energy beams or particles to destroy cancer cells or prevent them from growing. Radiation therapy can be delivered externally (external beam) or internally (brachytherapy) and is used as a primary treatment, as adjuvant therapy, or for symptom relief.

Recurrence

Cancer that has come back after a period of time during which it could not be detected. Recurrence can happen at the original site (local), in nearby areas (regional), or in distant organs (distant recurrence or metastatic recurrence).

Remission

A decrease in or disappearance of signs and symptoms of cancer. Partial remission means the cancer has shrunk but is still detectable. Complete remission means no cancer can be found on tests, though microscopic cancer cells may still be present.

Resection

The surgical removal of all or part of a tissue, organ, or tumour. For example, a liver resection removes part of the liver, and a bowel resection removes part of the colon.

S

Sarcoma

A cancer that arises in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Sarcomas are much less common than carcinomas.

Sentinel lymph node biopsy

A surgical procedure to determine whether cancer has spread to the lymph nodes. The sentinel node is the first lymph node to which cancer is most likely to spread from the primary tumour. If it is cancer-free, further lymph node removal may not be necessary.

Staging

The process of determining the size of a cancer and whether it has spread. Staging is one of the most important factors in deciding treatment options and predicting prognosis. Most solid tumours are staged using the TNM system (see below).

Survivorship

The phase of cancer care that begins after treatment ends. Survivorship includes follow-up monitoring, managing long-term side effects, emotional support, and maintaining overall health. A survivorship care plan outlines your follow-up schedule and what to watch for.

Systemic therapy

Treatment that travels through the bloodstream to reach cancer cells throughout the body. Chemotherapy, immunotherapy, targeted therapy, and hormone therapy are all forms of systemic therapy.

T

Targeted therapy

Cancer treatment that uses drugs designed to target specific molecules (such as proteins or gene mutations) involved in cancer cell growth and survival. Unlike chemotherapy, which affects all rapidly dividing cells, targeted therapy aims to attack cancer cells more precisely with fewer side effects.

Thrombocytopenia

An abnormally low platelet count. Thrombocytopenia can be a side effect of chemotherapy and increases the risk of bleeding. Symptoms include easy bruising, prolonged bleeding from cuts, and tiny red spots on the skin (petechiae).

TNM staging

The most widely used cancer staging system. T (Tumour) describes the size and extent of the primary tumour. N (Nodes) indicates whether cancer has spread to nearby lymph nodes. M (Metastasis) indicates whether cancer has spread to distant parts of the body. Together, TNM values determine the overall stage (I–IV).

Tumour

An abnormal mass of tissue. Tumours can be benign (not cancerous) or malignant (cancerous). Not all tumours require treatment, but all should be evaluated by a doctor.

Tumour board

A meeting in which a multidisciplinary team of doctors and specialists reviews a patient’s case and collectively recommends the best treatment approach. Having your case reviewed by a tumour board is considered best practice for complex cancer cases.

Tumour marker

A substance found in the blood, urine, or tissues that can be elevated in the presence of certain cancers. Examples include PSA (prostate cancer), CA-125 (ovarian cancer), and CEA (colon cancer). Tumour markers are used for screening, monitoring treatment response, and detecting recurrence.

U

Ultrasound

An imaging technique that uses sound waves to produce pictures of structures inside the body. Ultrasound is used to evaluate lumps, guide biopsies, and monitor certain cancers. It does not use radiation.

V

VEGF (vascular endothelial growth factor)

A protein that stimulates the growth of new blood vessels (angiogenesis). Tumours produce VEGF to build their own blood supply. Anti-VEGF drugs, such as bevacizumab, block this process and are used in the treatment of several cancers including colon cancer and kidney cancer.

W

Watchful waiting (active surveillance)

A strategy in which doctors closely monitor a cancer through regular tests and check-ups rather than starting treatment right away. This approach is used for certain slow-growing cancers, such as some forms of prostate cancer, where the risks of immediate treatment may outweigh the benefits.

White blood cell (WBC)

A type of blood cell that helps the body fight infection. Chemotherapy often lowers white blood cell counts, increasing the risk of infection. The most important type in this context is the neutrophil (see neutropenia).

X

X-ray

A type of imaging that uses small amounts of radiation to create pictures of structures inside the body. Chest X-rays are commonly used to evaluate lung conditions, though CT scans provide more detailed images for cancer diagnosis.

Last reviewed: March 2026. Medical terminology and definitions are based on information from the National Cancer Institute (NCI), American Cancer Society (ACS), and National Comprehensive Cancer Network (NCCN).