Glossary of Radiation Therapy Terms

The following is a brief list of some general terms and their definitions, taken from the American Cancer Society website. If you would like to see a full listing of cancer related terminology, please go to the American Cancer Society at: , under the section “Managing Your Cancer Experience”, select “Make Treatment Decisions,” then “Make Treatment Decisions,” again then select “Glossary” on the left hand side of the screen. Another very useful source is the National Cancer Institute’s dictionary, which can be found at .

Adenocarcinoma: (add-no-car-suh-NO-muh): cancer that starts in the glandular tissue, such as in the ducts or lobules of the breast.

Adjuvant therapy: (add-juh-vunt): treatment used in addition to the main treatment. It usually refers to hormonal therapy, chemotherapy, radiation therapy, or immunotherapy added after surgery to increase the chances of curing the disease or keeping it in check.

Advanced cancer: a general term describing stages of cancer in which the disease has spread from the primary site (where it started) to other parts of the body. When the cancer has spread only to nearby areas, it is called locally advanced. If it has spread to distant parts of the body, it is called metastatic.

Alopecia: (al-o-pee-shuh): hair loss. This often occurs as a result of chemotherapy or from radiation therapy to the head. In most cases, the hair grows back after treatment ends.

Alternative therapy: an unproven therapy that is recommended instead of standard (proven) therapy. Some alternative therapies have dangerous or even life-threatening side effects. With others, the main danger is that the patient may lose the chance to benefit from standard therapy. The American Cancer Society recommends that patients thinking about the use of any alternative or complementary therapy discuss this with their health care team. See also, complementary therapy.

Anemia: (uh-neem-ee-uh): low red blood cell count.

Anorexia: (an-uh-rek-see-uh): loss of appetite; may be caused by either the cancer itself or as a side effect of treatments such as chemotherapy.

Antibiotic: drugs used to kill organisms that cause disease. Antibiotics may be made by living organisms or they may be created in the lab. Since some cancer treatments can reduce the body’s ability to fight off infection, antibiotics may be used to treat or prevent these infections.

Benign tumor: (be-nine): an abnormal growth that is not cancer and does not spread to other areas of the body.

Biopsy: (buy-op-see): the removal of a sample of tissue to see whether cancer cells are present. There are several kinds of biopsies. In some, a very thin needle is used to draw fluid and cells from a lump. In a core biopsy, a larger needle is used to remove more tissue.

Blood count: a count of the number of red blood cells and white blood cells in a given sample of blood.

Bone marrow aspiration and biopsy: a procedure in which a needle is placed into the cavity of a bone, usually the hip or breast bone, to remove a small amount of bone marrow for examination under a microscope.

Bone marrow transplant: a treatment that restores blood-forming stem cells that have been destroyed by high doses of chemotherapy and/or radiation therapy. The bone marrow may come from the patient (autologous) or a donor (allogeneic.) See autologous bone marrow transplant, allogeneic bone marrow transplant, stem cell transplant.

Bone scan: an imaging method that gives important information about the bones, including the location of cancer that may have spread to the bones. It can be done on an outpatient basis and is painless, except for the needle stick when a low-dose radioactive substance is injected into a vein. Pictures are taken to see where the radioactivity collects, pointing to an abnormality.

Cancer: Cancer develops when cells in the body begin to grow out of control. Normal cells grow, divide, and die. Instead of dying, cancer cells continue to grow and form new abnormal cells. Cancer cells often travel to other body parts where they grow and replace normal tissue. This process, called metastasis, occurs as the cancer cells get into the bloodstream or lymph vessels. Cancer cells develop because of damage to DNA. DNA is in every cell and directs all its activities. When DNA becomes damaged the body is able to repair it. In cancer cells, the damage is not repaired. People can inherit damaged DNA, which accounts for inherited cancers. Many times, DNA becomes damaged by exposure to something in the environment, like smoking.

Carcinoma: (car-sin-o-ma): a malignant tumor that begins in the lining layer (epithelial cells) of organs. At least 80% of all cancers are carcinomas.

Chemotherapy: (key-mo-THER-uh-pee ): treatment with drugs to destroy cancer cells. Chemotherapy is often used with surgery or radiation to treat cancer when the cancer has spread, when it has come back (recurred), or when there is a strong chance that it could recur.

Clinical trials: Research studies test new drugs or treatments and compare them to current, standard treatments. Before a new treatment is used on people, it is studied in the lab. If lab studies suggest the treatment works, it is tested for patients. These human studies are called clinical trials. Questions the researchers want to answer are: Does this treatment work? Does it work better than the one we use now? What side effects does it cause? Do the benefits outweigh the risks? Your doctor may suggest a clinical trial. This doesn’t mean that you are a human guinea pig or that things are hopeless. There are risks. No one knows if the treatment will work or what side effects may occur. Remember, standard treatments, too, can have side effects.

Colony stimulating factors (CSF): types of growth factors that promote growth and division of blood-producing cells in the bone marrow. CSFs are naturally produced in the body. But extra amounts may be given as a treatment to reduce or prevent certain side effects of chemotherapy due to not having enough blood cells.

Complementary therapy: treatment used in addition to standard therapy. Some complementary therapies may help relieve certain symptoms of cancer, relieve side effects of standard cancer therapy, or improve a patient’s sense of well-being. The American Cancer Society recommends that patients considering use of any alternative or complementary therapy discuss this with their health care team, since many of these treatments are unproven and some can be harmful. See also alternative therapy.

Dietitian/registered dietitian/nutritionist: an expert in the area of food and diet; a registered dietitian (RD) has at least a bachelor’s degree and has passed a national competency exam. The term nutritionist is also used, but there are no educational requirements associated with this title.

Dosimetrist: (do-sim-uh-trist ): a person who plans and calculates the proper radiation dose for cancer treatment.

Emesis: (em-eh-sis ): vomiting

Five-year survival rate: the percentage of people with a given cancer who are expected to survive 5 years or longer after diagnosis. Five-year survival rates are based on the most recent information available, but they may include information from patients treated several years earlier. These numbers do not take into account advances in treatment that have often occurred. They are not helpful in predicting an individual case. They only paint a very general picture of how people in the past have done with the same type of cancer.

Gastrointestinal tract: (gas-tro-in-TEST-in-ul): the digestive tract. It consists of those organs and structures that process and prepare food to be used for energy; for example, the stomach, small intestine and large intestine.

Home health nurse: a nurse who give medications in the home, teaches patients how to care for themselves, and assesses their condition to see if further medical attention is needed.

Hospice: a special kind of care for people in the final phase of illness, their families and caregivers. The care may take place in the patient’s home or in a homelike facility.

Immune system: the complex system by which the body resists infection by germs such as bacteria or viruses and rejects transplanted tissues or organs. The immune system may also help the body fight some cancers.

Interstitial radiation therapy: (in-ter-stih-shul radiation therapy): a type of treatment in which a radioactive implant is placed directly into the tissue (not in a body cavity).

Invasive cancer: cancer that has spread beyond the layer of cells where it first developed to involve adjacent tissues.

Lesion: (lee-zhun): a change in body tissue; sometimes used as another word for tumor. May also be used to describe a change in the appearance or texture of skin, such as an open sore, scab, or discolored area.

Lymphatic system: the tissues and organs (including lymph nodes, spleen, thymus, and bone marrow) that produce and store lymphocytes (cells that fight infection) and the channels that carry the lymph fluid. The entire lymphatic system is an important part of the body’s immune system. Invasive cancers sometimes penetrate the lymphatic vessels (channels) and spread (metastasize) to lymph nodes.

Magnetic resonance imaging (MRI): a method of taking pictures of the inside of the body. Instead of using x-rays, MRI uses a powerful magnet to send radio waves through the body. The images appear on a computer screen as well as on film. Like x-rays, the procedure is physically painless, but some people may feel confined inside the MRI machine.

Metastasis: (meh-tas-teh-sis): cancer cells that have spread to one or more sites elsewhere in the body, often by way of the lymph system or bloodstream. Regional metastasis is cancer that has spread to the lymph nodes, tissues, or organs close to the primary site. Distant metastasis is cancer that has spread to organs or tissues that are farther away (such as when prostate cancer spreads to the bones, lungs, or liver).The plural of this word is metastases.

Neoadjuvant therapy: (nee-o-AD-juh-vunt): treatment given before the main treatment. Compare to adjuvant therapy.

Neutrophils: (new-trow-fils): white blood cells that fight bacterial infection.

Nuclear medicine scan: ( ): a method for localizing diseases of internal organs such as the brain, liver, or bone. Small amounts of a radioactive substance (isotope) are injected into the bloodstream. The isotope collects in certain organs and a special camera called scintillation camera is used to produce an image of the organ and detect areas of disease.

Nurse practitioner: a registered nurse with a master’s or doctoral degree. Licensed nurse practitioners diagnose and manage illness and disease, usually working closely with doctors.

Oncologist: (on-cahl-uh-jist): a doctor with special training in the diagnosis and treatment of cancer.

Pain specialist: oncologists, neurologists, anesthesiologists, neurosurgeons, and other doctors, nurses, or pharmacists who are experts in pain. A team of health professionals may also be available to address issues of pain control.

Palliative treatment: (pal-ee-uh-tiv): treatment that relieves symptoms, such as pain, but is not expected to cure the disease. Its main purpose is to improve the patient’s quality of life. Sometimes chemotherapy and radiation are used in this way.

Pathologist: (path-ahl-o-jist): a doctor who specializes in diagnosis and classification of diseases by lab tests such as examining cells under a microscope. The pathologist determines whether a tumor is benign or cancerous, and if cancerous the exact cell type and grade.

Physical therapist: a health professional who uses exercises and other methods to restore or maintain the body’s strength, mobility, and function.

Placebo: (pluh-see-bo): an inert, inactive substance that may be used in studies (clinical trials) to compare the effects of a given treatment with no treatment. In common speech, a “sugar pill.”

Platelet: (plate-uh-let): a part of the blood that plugs up holes in blood vessels after an injury. Chemotherapy can cause a drop in the platelet count, a condition called thrombocytopenia that carries a risk of excessive bleeding.

Positron emission tomography (PET): (pahs-uh-trahn uh-mish-uhn tom-agh-ruh-fee): a PET scan creates an image of the body (or of biochemical events) after the injection of a very low dose of a radioactive form of a substance such as glucose (sugar). The scan computes the rate at which the tumor is using the sugar. In general, high-grade tumors use more sugar than normal and low-grade tumors use less. PET scans are especially useful in taking images of the brain, although they are becoming more widely used to find the spread of cancer of the breast, colon, rectum, ovary, or lung. PET scans may also be used to see how well the tumor is responding to treatment.

Primary care physician: the doctor a person would normally see first when a problem arises. A primary care doctor could be a general practitioner, a family practice doctor, a gynecologist, a pediatrician, or an internal medicine doctor (an internest).

Primary site: the place where cancer begins. Primary cancer is usually named after the organ in which it starts. For example, cancer that starts in the breast is always breast cancer even if it spreads (metastasizes) to other organs such as bones or lungs.

Progression: spreading or growing disease, with or without treatment.

Prostate: (pros-tate): a gland found only in men. It is just below the bladder and in front of the rectum. The prostate makes a fluid that is part of semen. The tube that carries urine, the urethra, runs through the prostate.

Prostate specific antigen: a gland protein made primarily by the prostate. Levels of PSA may be elevated for a number of benign reasons or prostate cancer. The PSA test is used to help find prostate cancer as well as to monitor the results of treatment.

Radiation oncologist: a doctor who specializes in using radiation to treat cancer.

Radiation therapist: a person with special training to work the equipment that delivers radiation therapy.

Radiation therapy: treatment with high-energy rays (such as x-rays) to kill or shrink cancer cells. The radiation may come from outside of the body (external radiation) or from radioactive materials placed directly in the tumor (brachytherapy or internal radiation). Radiation therapy may be used as the main treatment for a cancer, to reduce the size of a cancer before surgery, or to destroy any remaining cancer cells after surgery. In advanced cancer cases, it may also be used as palliative treatment.

Radioactive implant: a source of high-dose radiation that is placed directly into or around a tumor to kill the cancer cells.

Radiologist: a doctor with special training in diagnosis of diseases by interpreting x-rays and other types of diagnostic imaging studies; for example, CT and MRI scans.

Recurrence: the return of cancer after treatment. Local recurrence means that the cancer has come back at the same place as the original cancer. Regional recurrence means that the cancer has come back after treatment in the lymph nodes near the primary site. Distant recurrence is when cancer metastasizes after treatment to distant organs or tissues (such as the lungs, liver, bone marrow, or brain).

Red blood cells: blood cells that contain hemoglobin, the substance that carries oxygen to all of the cells of the body.

Remission: complete or partial disappearance of the signs and symptoms of cancer in response to treatment; the period during which a disease is under control. A remission may not be a cure.

Scan: a study using either x-rays or radioactive isotopes to produce images of internal body organs.

Screening: the search for disease, such as cancer, in people without symptoms. For example, screening measures for prostate cancer include digital rectal examination and the PSA blood test; for breast cancer, mammograms and clinical breast exams. Screening may refer to coordinated programs in large groups of people.

Secondary tumor: a tumor that forms as a result of spread (metastasis) of cancer from the place where it started.

Social worker: a health professional who helps people find community resources and provides counseling and guidance to assist with issues such as insurance coverage and nursing home placement.

Staging: the process of finding out whether cancer has spread and if so, how far; that is, to learn the stage of the cancer. There is more than one system for staging different types of cancer. The most commonly used is the TNM system.

Survival rate: the percentage of people still alive within a certain period of time after diagnosis or treatment. For cancer, a 5-year survival rate is often given. This does not mean that people can’t live more than 5 years, or that those who live for 5 years are necessarily permanently cured.

Systemic therapy: treatment that reaches and affects cells throughout the body; for example, chemotherapy.

Therapy: any of the measures taken to treat a disease.

Thrombocytopenia: (throm-bo-sigh-toe-PEEN-e-uh): a decrease in the number of platelets in the blood; can be a side effect of chemotherapy.

Tumor: an abnormal lump or mass of tissue. Tumors can be benign (non-cancerous) or malignant (cancerous).

Tumor markers: substance produced by cancer cells and sometimes normal cells. They are not very useful for cancer screening because other body tissues not related to a cancer can produce the substance. But tumor markers may be very useful in monitoring for response to treatment when a cancer is diagnosed or for a recurrence. Tumor markers include CA 125 (ovarian cancer), CEA (GI tract cancers), and PSA (prostate cancer).

Ultrasound: an imaging method in which high-frequency sound waves are used to outline a part of the body. The sound wave echoes are picked up and displayed on a television screen. Also called ultrasonography.

Virus: very small organisms that cause infections. Viruses are too small to be seen with a regular microscope. They reproduce only in living cells.

White blood cells: that help defend the body against infections. There are several types of white blood cells. Certain cancer treatments such as chemotherapy can reduce the number of these cells and make a person more likely to get infections.

X-rays: one form of radiation that can be used at low levels to produce an image of the body on film or at high levels to destroy cancer cells.