Glossary

Click one of the letters above to advance the page to terms beginning with that letter.

A

ablation (a-BLAY-shun)
In medicine, the removal or destruction of a body part or tissue or its function. Ablation may be performed by surgery, hormones, drugs, radiofrequency, heat, or other methods. (NCI)
accelerated radiation therapy
Radiation treatment in which the total dose of radiation is given over a shorter period of time (fewer days) compared to standard radiation therapy. (NCI)
accelerated-fraction radiation therapy
Radiation treatment in which the total dose of radiation is divided into small doses and the treatments are given more than once a day. The total dose of radiation is also given over a shorter period of time (fewer days) compared to standard radiation therapy. (NCI)
adenocarcinoma (A-den-oh-KAR-sih-NOH-muh)
Cancer that begins in cells that line certain internal organs and that have gland-like (secretory) properties. (NCI)
adenosquamous carcinoma (A-den-oh-SKWAY-mus KAR-sih-NOH-muh)
A type of cancer that contains two types of cells: squamous cells (thin, flat cells that line certain organs) and gland-like cells. (NCI)
adjuvant therapy (A-joo-vant THAYR-uh-pee)
Additional cancer treatment given after the primary treatment to lower the risk that the cancer will come back. Adjuvant therapy may include chemotherapy, radiation therapy, hormone therapy, targeted therapy, or biological therapy. Also called adjunct therapy or adjunctive therapy. (NCI)
advanced cancer
Cancer that has spread to other places in the body and usually cannot be cured or controlled with treatment. (NCI)
aggressive (uh-GREH-siv)
A quickly growing cancer. (NCI)
APBI
Also called accelerated partial breast irradiation, is a hyperfractionated regime performed in five to 10 sessions (usually 10 sessions in 5 days). With APBI, the radiation is delivered at a higher overall dose rate over a shorter period of time compared to conventional radiation therapy.
arteriovenous malformation (ar-teer-ee-OH-vee-nus)
A defect of the circulatory system where arteries and veins become tangled in a mass. Arteries carry oxygen-rich blood away from the heart to the body's cells; veins return oxygen-depleted blood to the lungs and heart. The presence of an AVM disrupts this vital cyclical process. Those located in the brain or spinal cord can have especially widespread effects on the body.

B

Barrett esophagus (BA-ret ee-SAH-fuh-gus)
A condition in which the cells lining the lower part of the esophagus have changed or been replaced with abnormal cells that could lead to cancer of the esophagus. The backing up of stomach contents (reflux) may irritate the esophagus and, over time, cause Barrett esophagus. (NCI)
benign (beh-NINE)
Not cancerous. Benign tumors may grow larger but do not spread to other parts of the body. Also called nonmalignant.
bilateral cancer (by-LA-teh-rul KAN-ser)
Cancer that occurs in both paired organs, such as both breasts or both ovaries. (NCI)
brachytherapy (BRAY-kee-THAYR-uh-pee)
Also called implant radiation therapy, internal radiation therapy, and radiation brachytherapy. A type of radiation therapy in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. (NCI)
breast cancer
Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare. (NCI)

C

cancer
A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. Also called malignancy. (NCI)
cancer of unknown primary origin
A case in which cancer cells are found in the body, but the place where the cells first started growing (the origin or primary site) cannot be determined. Also called carcinoma of unknown primary and CUP. (NCI)
carcinoma in situ (KAR-sih-NOH-muh in SY-too)
A group of abnormal cells that remain in the place where they first formed. They have not spread. These abnormal cells may become cancer and spread into nearby normal tissue. Also called stage 0 disease. (NCI)
CAT scan
A series of detailed pictures of areas inside the body taken from different angles. The pic-tures are created by a computer linked to an x-ray machine. Also called computed tomo-graphy scan, computerized axial tomography scan, computerized tomography, and CT scan. (NCI)
cell
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells. (NCI)
cell cycle
The process a cell goes through each time it divides. The cell cycle consists of a series of steps during which the chromosomes and other cell material double to make two copies. The cell then divides into two daughter cells, each receiving one copy of the doubled ma-terial. The cell cycle is complete when each daughter cell is surrounded by its own outer membrane. Also called mitotic cycle. (NCI)
clinician (klih-NIH-shun)
A health professional who takes care of patients. (NCI)
concurrent therapy
A treatment that is given at the same time as another. (NCI)
cumulative dose
In medicine, the total amount of a drug or radiation given to a patient over time; for example, the total dose of radiation given in a series of radiation treatments. (NCI)
cumulative exposure
The total amount of a substance or radiation that a person is exposed to over time. Cumulative exposure to a harmful substance or radiation may increase the risk of certain diseases or conditions. (NCI)

D

definitive treatment
The treatment plan for a disease or disorder that has been chosen as the best one for a patient after all other choices have been considered. (NCI)
DNA
The molecules inside cells that carry genetic information and pass it from one generation to the next. Also called deoxyribonucleic acid. (NCI)
dose
the amount of radiation received
dosimetrist (do-SIM-uh-trist)
A person who determines the proper radiation dose for treatment. (NCI)
dosimetry (doh-SIH-muh-tree)
Measurement of radiation exposure from x-rays, gamma rays, or other types of radiation used in the treatment or detection of diseases, including cancer. (NCI)

E

early-stage
A term used to describe cancer that is early in its growth, and may not have spread to other parts of the body. What is called early stage may differ between cancer types. (NCI)
electron beam
A stream of electrons (small negatively charged particles found in atoms) that can be used for radiation therapy. (NCI)
external-beam radiation therapy
A type of radiation therapy that uses a machine to aim high-energy rays at the cancer from outside of the body. Also called external radiation therapy. (NCI)

F

follow-up
Monitoring a person's health over time after treatment. This includes keeping track of the health of people who participate in a clinical study or clinical trial for a period of time, both during the study and after the study ends. (NCI)
fractionation (FRAK-shun-AY-shun)
Dividing the total dose of radiation therapy into several smaller, equal doses delivered over a period of several days. (NCI)

G

gantry

The part of the accelerator out of which the radiation beam comes is called a gantry, which can be rotated around the patient. Radiation can be delivered to the tumor from any angle by rotating the gantry and moving the treatment couch.

H

head and neck cancer
Cancer that arises in the head or neck region (in the nasal cavity, sinuses, lips, mouth, salivary glands, throat, or larynx [voice box]). (NCI)
high-dose radiation
Also called HDR. An amount of radiation that is greater than that given in typical radiation therapy. High-dose radiation is precisely directed at the tumor to avoid damaging healthy tissue, and may kill more cancer cells in fewer treatments. (NCI)
high-dose-rate remote brachytherapy (BRAY-kee-THAYR-uh-pee)
A type of internal radiation treatment in which the radioactive source is removed between treatments. Also called high-dose-rate remote radiation therapy and remote brachytherapy. (NCI)
hormonal therapy
Treatment that adds, blocks, or removes hormones. For certain conditions (such as diabetes or menopause), hormones are given to adjust low hormone levels. To slow or stop the growth of certain cancers (such as prostate and breast cancer), synthetic hormones or other drugs may be given to block the body's natural hormones. Sometimes surgery is needed to remove the gland that makes a certain hormone. Also called endocrine therapy, hormone therapy, and hormone treatment. (NCI)
hyperfractionated radiation therapy (HY-per-FRAK-shun-AYT-ed RAY-dee-AY-shun THAYR-uh-pee)
Radiation treatment in which the total dose of radiation is divided into small doses and treatments are given more than once a day. Also called hyperfractionation and superfractionated radiation therapy. (NCI)
hyperfractionation (HY-per-FRAK-shun-AY-shun)
Also called hyperfractionated radiation therapy and superfractionated radiation therapy. Radiation treatment in which the total dose of radiation is divided into small doses and treatments are given more than once a day. (NCI)

I

IGRT
Also called image-guided radiation therapy. A procedure that uses a computer to create a picture of a tumor to help guide the radiation beam during radiation therapy. The pictures are made using CT, ultrasound, X-ray, or other imaging techniques. Image-guided radiation therapy makes radiation therapy more accurate and causes less damage to healthy tissue. (NCI)
imaging
In medicine, a process that makes pictures of areas inside the body. Imaging uses methods such as x-rays (high-energy radiation), ultrasound (high-energy sound waves), and radio waves. (NCI)
IMRT
Also called intensity-modulated radiation therapy. A type of 3-dimensional radiation therapy that uses computer-generated images to show the size and shape of the tumor. Thin beams of radiation of different intensities are aimed at the tumor from many angles. This type of radiation therapy reduces the damage to healthy tissue near the tumor. (NCI)
internal radiation therapy (in-TER-nul RAY-dee-AY-shun THAYR-uh-pee)
A type of radiation therapy in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. Also called brachytherapy, implant radiation therapy, and radiation brachytherapy. (NCI)

L

linac
A machine that uses electricity to form a stream of fast-moving subatomic particles. This creates high-energy radiation that may be used to treat cancer. Also called linear accelerator, mega-voltage linear accelerator, and MeV linear accelerator. (NCI)
linear accelerator
A machine that uses electricity to form a stream of fast-moving subatomic particles. This creates high-energy radiation that may be used to treat cancer. Also called linac, mega-voltage linear accelerator, and MeV linear accelerator. (NCI)
lymphedema
Refers to swelling that generally occurs in one of your arms or legs. Although lymphedema tends to affect just one arm or leg, sometimes both arms or both legs may be swollen. Lymphedema is caused by a blockage in your lymphatic system, an important part of your immune and circulatory systems. The blockage prevents lymph fluid from draining well, and as the fluid builds up, the swelling continues.
lymphoepithelioma (LIM-foh-EH-pih-THEE-lee-OH-muh)
A type of cancer that begins in the tissues covering the nasopharynx (the upper part of the throat behind the nose). (NCI)

M

malignant (muh-LIG-nunt)
Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.
medical oncologist
A doctor who specializes in diagnosing and treating cancer using chemotherapy, hormonal therapy, biological therapy, and targeted therapy. A medical oncologist often is the main health care provider for someone who has cancer. A medical oncologist also gives supportive care and may coordinate treatment given by other specialists. (NCI)
medical physicist
An expert who works with the dosimetrist and the radiation oncologist to measure the precision of your treatment plan, and works with the equipment to calculate the best angles to treat your tumor, or tumor site. The medical physicist also runs frequent safety checks and makes sure that the equipment is working properly.
meningeal (meh-NIN-jee-ul)
Having to do with the meninges (three thin layers of tissue that cover and protect the brain and spinal cord). (NCI)
meningeal metastasis (meh-NIN-jee-ul meh-TAS-tuh-sis)
A serious problem that may occur in cancer in which cancer cells spread from the original (primary) tumor to the meninges (thin layers of tissue that cover and protect the brain and spinal cord). It can happen in many types of cancer, but is the most common in melanoma, breast, lung, and gastrointestinal cancer. The cancer may cause the meninges to be inflamed. Also called carcinomatous meningitis, leptomeningeal carcinoma, leptomeningeal metastasis, meningeal carcinomatosis, and neoplastic meningitis. (NCI)
metastasis (meh-TAS-tuh-sis)
The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a metastatic tumor or a metastasis. The metastatic tumor contains cells that are like those in the original (primary) tumor. The plural form of metastasis is metastases (meh-TAS-tuh-SEEZ). (NCI)
metastasize (meh-TAS-tuh-size)
To spread from one part of the body to another. When cancer cells metastasize and form secondary tumors, the cells in the metastatic tumor are like those in the original (primary) tumor. (NCI)
metastatic (meh-tuh-STA-tik)
Having to do with metastasis, which is the spread of cancer from the primary site (place where it started) to other places in the body. (NCI)
MRI
Also called magnetic resonance imaging, NMRI, and nuclear magnetic resonance imaging. A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. (NCI)
multi-leaf collimator
A device inside of a linear accelerator gantry that helps to conform a radiation beam to a specific shape. Thin, individual platelets, or 'leaves' shift into place, creating a unique beam shape based on the size and contours of a particular tumor.

N

noninvasive
In medicine, it describes a procedure that does not require inserting an instrument through the skin or into a body opening. In cancer, it describes disease that has not spread outside the tissue in which it began. (NCI)

O

On-Board Imager (OBI)
The OBI system is mounted onto a linear accelerator via robotically controlled arms. The OBI takes a 3-D image of the patient and his or her tumor position before and sometimes during treatment.
oncologist
A doctor who specializes in treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation. (NCI)
ovarian cancer
Cancer that forms in tissues of the ovary (one of a pair of female reproductive glands in which the ova, or eggs, are formed). Most ovarian cancers are either ovarian epithelial carcinomas (cancer that begins in the cells on the surface of the ovary) or malignant germ cell tumors (cancer that begins in egg cells). (NCI)

P

palliative care or therapy (PA-lee-uh-tiv)
Also called comfort care, supportive care, and symptom management. Care given to im-prove the quality of life of patients who have a serious or life-threatening disease. The goal of palliative care is to prevent or treat as early as possible the symptoms of a disease, side effects caused by treatment of a disease, and psychological, social, and spiritual problems related to a disease or its treatment.
partial mastectomy
Also called segmental mastectomy. The removal of cancer as well as some of the breast tissue around the tumor and the lining over the chest muscles below the tumor. Usually some of the lymph nodes under the arm are also taken out. (NCI)
pathology report (puh-THAH-loh-jee ...)
The description of cells and tissues made by a pathologist based on microscopic evidence, and sometimes used to make a diagnosis of a disease. (NCI)
PET scan
Also called positron emission tomography scan. A procedure in which a small amount of radioactive glucose (sugar) is injected into a vein, and a scanner is used to make detailed, computerized pictures of areas inside the body where the glucose is used. Because cancer cells often use more glucose than normal cells, the pictures can be used to find cancer cells in the body. (NCI)
pharynx (FAYR-inx)
The hollow tube inside the neck that starts behind the nose and ends at the top of the trachea (windpipe) and esophagus (the tube that goes to the stomach). The pharynx is about 5 inches long, depending on body size. Also called throat. (NCI)
prostate cancer
Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men. (NCI)
proton therapy

Proton therapy, also called proton beam therapy, is a type of radiation treatment that uses protons rather than x-rays to treat cancer. A proton is a positively charged particle. At high energy, protons can destroy cancer cells.

R

radiation (RAY-dee-AY-shun)
Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable). (NCI)
radiation enteritis (EN-tuh-RY-tis)
Inflammation of the small intestine caused by radiation therapy to the abdomen, pelvis, or rectum. Symptoms include nausea, vomiting, abdominal pain and cramping, frequent bowel movements, watery or bloody diarrhea, fatty stools, and weight loss. Some of these symptoms may continue for a long time. (NCI)
radiation fibrosis
The formation of scar tissue as a result of radiation therapy. (NCI)
radiation necrosis
The death of healthy tissue caused by radiation therapy. Radiation necrosis is a side effect of radiation therapy given to kill cancer cells, and can occur after cancer treatment has ended. (NCI)
radiation nurse
A health professional who specializes in caring for people who are receiving radiation therapy. (NCI)
radiation oncologist
A doctor who specializes in using radiation to treat cancer.
radiation physicist
A person who makes sure that the radiation machine delivers the right amount of radiation to the correct site in the body. The physicist works with the radiation oncologist to choose the treatment schedule and dose that has the best chance of killing the most cancer cells. (NCI)
radiation therapist
A health professional who gives radiation treatment. (NCI)
radiation therapy
Also called radiotherapy and irradiation. The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. (NCI)
radioactive seed
A small, radioactive pellet that is placed in or near a tumor. Cancer cells are killed by the energy given off as the radioactive material breaks down and becomes more stable. (NCI)
radiologist (RAY-dee-AH-loh-jist)
A doctor who specializes in creating and interpreting pictures of areas inside the body. The pictures are produced with x-rays, sound waves, or other types of energy. (NCI)
radiosurgery (RAY-dee-oh-SER-juh-ree)
Also called radiation surgery, or stereotactic radiosurgery. A type of external radiation therapy that uses special equipment or a linac, to position the patient and precisely give a 1-5 large doses of radiation to a tumor. It was first used to treat brain tumors and other brain disorders that could not be treated by regular surgery. It is also being studied in the treatment of other types of cancer. (NCI)
Radiotherapy
Also called radiation therapy. The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. (NCI)
remission
A decrease in or disappearance of signs and symptoms of cancer. In partial remission, some, but not all, signs and symptoms of cancer have disappeared. In complete remission, all signs and symptoms of cancer have disappeared, although cancer still may be in the body. (NCI)
remote brachytherapy (...BRA-kee-THAYR-uh-pee)
Also called high-dose-rate remote brachytherapy and high-dose-rate remote radiation therapy. A type of internal radiation treatment in which the radioactive source is removed between treatments. (NCI)
respiratory gating
This technology enables clinicians to track a tumor's position in relation to the patient's respiratory cycle. Using an infrared tracking camera and a reflective marker on the patient's torso, the system measures the breathing pattern and range of motion. When the tumor is in the desired portion of the respiratory cycle, the gating system turns the treatment beam on and off. This helps with treatment of the lungs, liver, and pancreas, and helps minimize the dose to the heart in breast treatments.

S

salivary gland cancer (SA-lih-VAYR-ee gland KAN-ser)
A rare cancer that forms in tissues of a salivary gland (gland in the mouth that makes saliva). Most salivary gland cancers occur in older people. (NCI)
scan
A picture of structures inside the body. Scans often used in diagnosing, staging, and monitoring disease include liver scans, bone scans, and computed tomography (CT) or computerized axial tomography (CAT) scans and magnetic resonance imaging (MRI) scans. In liver scanning and bone scanning, radioactive substances that are injected into the bloodstream collect in these organs. A scanner that detects the radiation is used to create pictures. In CT scanning, an x-ray machine linked to a computer is used to produce detailed pictures of organs inside the body. MRI scans use a large magnet connected to a computer to create pictures of areas inside the body. (NCI)
screening mammogram
X-rays of the breasts taken to check for breast cancer in the absence of signs or symptoms. (NCI)
simulation
In cancer treatment, a process used to plan radiation therapy so that the target area is precisely located and marked. (NCI)
sinus
A cavity, space, or channel in the body. Examples include hollow spaces in the bones at the front of the skull, and channels for blood and lymph. Sinuses may also be found in the heart, brain, and other organs. (NCI)
small cell lung cancer
An aggressive (fast-growing) cancer that forms in tissues of the lung and can spread to other parts of the body. The cancer cells look small and oval-shaped when looked at under a microscope. (NCI)
spinal cancer
Cancer that begins in the spinal column (backbone) or spinal cord. The spinal column is made up of linked bones, called vertebrae. The spinal cord is a column of nerve tissue that runs from the base of the skull down the back. It is surrounded by three protective membranes, and is enclosed within the vertebrae. Many different types of cancer may form in the bones, tissues, fluid, or nerves of the spine. (NCI)
spiral CT scan
Also called helical computed tomography. A detailed picture of areas inside the body. The pictures are created by a computer linked to an x-ray machine that scans the body in a spiral path. (NCI)
squamous cell carcinoma (SKWAY-mus sel KAR-sih-NOH-muh)
Also called epidermoid carcinoma. Cancer that begins in squamous cells, which are thin, flat cells that look like fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of the hollow organs of the body, and the passages of the respiratory and digestive tracts. (NCI)
squamous cell carcinoma of the head and neck (SKWAY-mus sel KAR-sih-NOH-muh )
Cancer of the head and neck that begins in squamous cells (thin, flat cells that form the surface of the skin, eyes, various internal organs, and the lining of hollow organs and ducts of some glands). Squamous cell carcinoma of the head and neck includes cancers of the nasal cavity, sinuses, lips, mouth, salivary glands, throat, and larynx (voice box). Most head and neck cancers are squamous cell carcinomas.
stage
The extent of a cancer in the body. Staging is usually based on the size of the tumor, whether lymph nodes contain cancer, and whether the cancer has spread from the original site to other parts of the body. (NCI)
staging
Performing exams and tests to learn the extent of the cancer within the body, especially whether the disease has spread from the original site to other parts of the body. It is important to know the stage of the disease in order to plan the best treatment. (NCI)
stereotactic body radiation therapy (STAYR-ee-oh-TAK-tik BAH-dee RAY-dee-AY-shun THAYR-uh-pee)
A type of external radiation therapy that uses special equipment to position a patient and precisely deliver radiation to tumors in the body (except the brain). The total dose of radiation is divided into smaller doses given over several days. This type of radiation therapy helps spare normal tissue. (NCI)
stereotactic radiation therapy (STAYR-ee-oh-TAK-tik RAY-dee-AY-shun THAYR-uh-pee)
Also called stereotactic external-beam radiation therapy. A type of external radiation therapy that uses special equipment to position the patient and precisely deliver radiation to a tumor. The total dose of radiation is divided into several smaller doses given over several days.

T

throat cancer
Also called pharyngeal cancer. Cancer that forms in tissues of the pharynx (the hollow tube inside the neck that starts behind the nose and ends at the top of the windpipe and esophagus). Throat cancer includes cancer of the nasopharynx (the upper part of the throat behind the nose), the oropharynx (the middle part of the pharynx), and the hypopharynx (the bottom part of the pharynx). Cancer of the larynx (voice box) may also be included as a type of throat cancer. Most throat cancers are squamous cell carcinomas (cancer that begins in thin, flat cells that look like fish scales). (NCI)
thyroid cancer
Cancer that forms in the thyroid gland (an organ at the base of the throat that makes hormones that help control heart rate, blood pressure, body temperature, and weight). Four main types of thyroid cancer are papillary, follicular, medullary, and anaplastic thyroid cancer. The four types are based on how the cancer cells look under a microscope. (NCI)
tongue cancer
Cancer that begins in the tongue. When the cancer begins in the front two-thirds of the tongue, it is considered to be a type of oral cavity cancer; when the cancer begins in the back third of the tongue, it is considered to be a type of oropharyngeal or throat cancer. (NCI)
trigeminal neuralgia
A nerve disorder that causes a stabbing or electric-shock-like pain in parts of the face. Radiosurgery can be used to treat the trigeminal nerve and stop chronic pain.
tumor (TOO-mer)
An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancer), or malignant (cancer). Also called neoplasm. (NCI)

U

ultrasound (UL-truh-SOWND)
A procedure in which high-energy sound waves are bounced off internal tissues or organs and make echoes. The echo patterns are shown on the screen of an ultrasound machine, forming a picture of body tissues called a sonogram. Also called ultrasonography. (NCI)

X

x-ray
A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer. (NCI)
xerostomia
Dry mouth. It occurs when the body is not able to make enough saliva.