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Cancer Glossary

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Ranges from light and heat to radio waves, microwaves, and x-rays. In reference to cancer, the 2 main types are ionizing and non-ionizing radiation. The high-energy rays used for x-rays and some other imaging tests, as well as in higher doses for cancer treatment, are called ionizing radiation. This type of radiation can be produced by medical devices, but also comes from natural sources such as radon gas (in the ground) and outer space. See also imaging tests, radiation dose, radiation therapy, x-ray.
The amount of radiation an object (such as human tissue) receives. Several units are used to describe radiation doses, as listed below.

  • rad (short for radiation absorbed dose) – a basic unit of the amount of radiation transferred to an object. This measurement does not take into account the type of radiation, which can influence the effect on different body tissues. The rad has largely been replaced by the gray measurement scale (see next).

  • gray (abbreviated Gy) – the newer, international unit of measurement of radiation transfer. One gray equals 100 rads, and a centigray is 1/100th of a gray. So, one rad equals one centigray (cGy). 1/1000 of a gray is called a milligray (mGy).

  • rem (short for roentgen equivalent man) – a basic unit of radiation exposure which is based on both the dose and the type of radiation. Because of this, it’s more commonly used to describe radiation exposure in humans than is the rad. Often reported in units of millirem (mrem), which is 1/1000 of a rem. The rem is sometimes replaced by the sievert (see next).

  • sievert (see-vert) abbreviated Sv. A newer, international unit of measurement of human radiation exposure. One sievert equals 100 rem. Often reported in millisieverts (mSv), which are thousandths of a sievert (or 1/10 of a rem).
  •  Search  [RAY-dee-A-shun on-KAHL-uh-jist]
    A doctor who specializes in using radiation to treat cancer. See also cancer care team.
     Search  [RAY-dee-A-shun NEW-muh-NI-tis]
    A side effect of radiation therapy to the chest area.There is inflammation of the lungs that may not cause problems, but can cause cough, shortness of breath, and fever. It may occur from a few weeks to up to 6 months after external radiation therapy. See also radiation therapy.
     Search  [RAY-dee-A-shun prok-TIE-tis]
    A possible side effect of radiation therapy to the pelvic area. There is inflammation of the rectum and anus and problems can include pain, frequent bowel movements, bowel urgency, bleeding, chronic burning, or rectal leakage. See also anus, pelvis, radiation therapy, rectum.
     Search  [RAY-dee-A-shun THER-uh-pist]
    A person with special training to use the equipment that delivers radiation therapy.
     Search  [RAY-dee-A-shun THER-uh-pee]
    Treatment with high-energy rays or particles to kill cancer cells and shrink tumors. The radiation may come from outside the body (external radiation) or from radioactive materials placed in the body (brachytherapy or internal radiation). See also brachytherapy, external beam radiation therapy, intensity modulated radiation therapy, radiation dose, three-dimensional conformal radiation therapy, x-ray.
     Search  [RAD-ick-uhl PAIR-uh-NEE-ul PROS-tuh-TECK-tuh-me]
    Surgery to remove the prostate through a cut (incision) in the perineum (the skin behind the testicles). This approach is used less often than others, in part because it makes it harder for the surgeon to spare the nerves that control erections. See also neurovascular bundles, nerve-sparing prostatectomy, perineum, prostate, radical prostatectomy, retropubic prostatectomy, testicles.
     Search  [RAD-ick-uhl PROS-tuh-TECK-tuh-me]
    Surgery to remove the entire prostate gland, the seminal vesicles, and nearby tissue. See also prostate, seminal vesicles.
     Search  [RAY-dee-o-ACT-iv IM-plant]
    A source of ionizing radiation that’s placed in or around a tumor to kill the cancer cells. See also brachytherapy, radiation therapy.
     Search  [RAY-dee-o-CON-trast]
    Also called dye, contrast dye, radiocontrast medium. Any material used in imaging tests such as x-rays, MRIs, and CT scans to help outline the body parts being examined. These may be injected, put into the rectum, or ingested (drunk). See also imaging tests.
     Search  [RAY-dee-oh-FREE-kwin-see uh-BLAY-shun]
    Often shortened to RFA. Treatment that uses high-energy radio waves to heat and destroy abnormal tissues. In cancer treatment, a thin, needle-like probe is guided into the tumor using ultrasound or a computed tomography (CT) scan. A high-frequency current is then passed through the probe, which heats and kills nearby cells. See also computed tomography scan, ultrasound.
     Search  [RAY-dee-oh-EYE-suh-TOPE]
    Also called a radionuclide (RAY-dee-oh-NOO-klide). A type of atom that’s unstable and prone to break up (decay). Decay releases small fragments of atoms and radiation energy. Exposure to certain radioisotopes can cause cancer. But radioisotopes are also used to find and treat cancer. In certain imaging tests, for example, radioisotopes are injected into the body where they then collect in areas where the disease is active, showing up as brighter areas on the pictures. See also imaging tests, nuclear medicine scan, radiation.
     Search  [RAY-dee-uh-LAH-jick teck-NAH-luh-jist]
    A health professional who positions patients for x-rays and other imaging tests, takes the images, and then checks the images for quality. The pictures taken by the technologist are typically sent to a radiologist to be read. See also radiologist, x-ray.
     Search  [RAY-dee-AH-luh-jist]
    A doctor with special training in diagnosis of diseases by interpreting or reading x-rays and other types of imaging tests. See also imaging tests, x-ray.
     Search  [RAY-dee-oh-NOO-klide]
    See bone scan.
     Search  [RAY-dee-oh-FARM-uh-SUIT-ih-kulz]
    A group of drugs that include radioactive elements or radioisotopes, such as strontium-89 or samarium-153, which are given into a vein (intravenously or IV) to help treat certain types of cancer (often cancers that have spread to the bones). See also radioisotope, strontium-89.
     Search  [RAY-dee-oh-SENS-ih-TIV-it-tee]
    How susceptible a cell is to radiation, or how easy it is for radiation to kill the cell. Cells that divide frequently are especially radiosensitive and are more affected by radiation. See also cell, radiation therapy.
     Search  [RAY-dee-oh-SENS-it-tie-zer]
    Also called a radiosensitizing agent. A substance that makes cancer cells easier to kill with radiation therapy. See also cell, radiation therapy, radiosensitivity.
    See radiation therapy.
     Search  [RAY-dee-us]
    In the human body, the bone in the forearm (connecting the elbow and the wrist) that’s nearest to the thumb. Compare to ulna.
    A process in clinical trials that uses chance to assign participants to different groups that compare treatments. Randomization means that a person is assigned randomly to the treatment or control groups rather than based on a factor that might change the results. This helps reduce bias in the results that might happen, if, for example, the healthiest people all were assigned to a particular treatment group. See also clinical trials, control group.
    Surgery to remove cancer in the rectum, which is often the main treatment for this cancer. Radiation and chemotherapy may be given before or after surgery. See also adjuvant therapy, chemotherapy, neoadjuvant therapy, radiation, rectum.
    The last part of the large intestine, between the sigmoid colon and the anus. See also anus, colon, intestines, sigmoid colon.
    The return of cancer after treatment. Local recurrence means that the cancer has come back at the same place as the original cancer (primary site). Regional recurrence means that the cancer has come back in nearby tissues or lymph nodes near the primary site. Distant recurrence is when cancer comes back in distant organs or tissues. See also lymph node, metastasis, metastasize, primary site.
     Search  [RBCs]
    Blood cells that contain hemoglobin, the substance that carries oxygen to all of the cells of the body. These cells are made in the bone marrow. A low red blood cell count, called anemia, can have many causes, including cancer and some cancer treatments. See also anemia, blood count, bone marrow.
    Doses of radiation or chemotherapy given before an allogeneic stem cell transplant, in which lower doses are used to leave some of the patient’s bone marrow cells while the new marrow takes hold. See also bone marrow, chemotherapy, conditioning treatment, hematopoietic stem cell transplant, mini-transplant, radiation.
    See mammoplasty.
    A second surgery to remove remaining cancer. This may be done if cancer cells were found at the edge of surgically removed tissue. See also excision, surgical margin.
     Search  [ree-FRACK-tuh-re]
    No longer responsive to a certain treatment. See also drug resistance.
     Search  [REH-juh-men]
    A regulated plan (such as diet, exercise, or a medicine schedule) designed to reach certain goals. In cancer treatment, a treatment plan which might include different medicines given on a certain schedule, as well as other treatments such as radiation. See also protocol.
    Also called regional spread. The spread of cancer from where it started (primary site) to nearby areas such as lymph nodes, but not to distant sites. See also lymph node, metastasis, primary site.
     Search  [ree-GRESH-un]
    Decrease in the size of the tumor or the extent of the cancer.
     Search  [REE-huh-BILL-ih-TAY-shun]
    Activities to help a person adjust, heal, and return to a full, productive life after injury or illness. This could include physical restoration (such as the use of prostheses, exercises, and physical therapy), counseling, and emotional support. See also prosthesis, physical therapist, occupational therapist.
     Search  [REE-laps]
    Reappearance of cancer or other disease after a disease-free period. See also recurrence.
    See radiation dose.
     Search  [re-MISH-un]
    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.
     Search  [REE-nul]
    Having to do with the kidneys.
     Search  [REP-lih-KATE]
    To reproduce exact copies.
    In cancer care, procedures or treatments such as a stem cell transplant that “rescue” a patient’s immune system and blood-forming organs by correcting the damage caused by high-dose chemotherapy. See also chemotherapy, hematopoietic stem cell transplant, immune system.
     Search  [re-SEK-shun]
    Surgery to remove part or all of an organ or other structure.
     Search  [re-SEK-tuh-SCOPE]
    A long, thin instrument with a light and lens on the end that can be passed into the urethra. It’s used for transurethral resection of the prostate (TURP) and to remove some lesions in the bladder, uterus, or urethra. It allows the surgeon to look at the inside of the urethra, the bladder, the uterus, and some of the prostate; a wire loop on the end can be used to remove abnormal tissue. See also bladder, lesion, prostate, transurethral resection of the prostate, urethra, uterus.
     Search  [RES-per-uh-TOR-ee THAIR-uh-pist]
    A health professional who, under the direction of a doctor, gives breathing treatments and helps manage patients on breathing machines (ventilators or respirators).
     Search  [RES-pit]
    The short-term care of a sick person to provide a break (respite) to the regular caregiver(s). Respite care may be given in a nursing home, hospital, or even in the home by substitute care providers.
    Outcome after treatment, or the reaction to a drug or any other therapy.
    See urinary retention.
     Search  [RET-in-oh-blast-OH-muh]
    A type of cancer that starts in the nerve cells lining the back of the eyeball (retina). It’s most often seen in infants and young children, and can sometimes be passed on in families (inherited).
     Search  [RET-in-oyds]
    Vitamin A and man-made (synthetic) compounds similar to vitamin A.
     Search  [RET-tro-grade e-JACK-you-LAY-shun]
    A condition in men, often happening after some types of pelvic surgery or radiation, in which semen enters the bladder during orgasm, rather than leaving the body through the penis. See also bladder, prostate, radiation, semen.
     Search  [RET-tro-PEW-bick]
    Behind the pubic bone but in front of the bladder. In prostate cancer, a surgical approach to remove the prostate through a cut (incision) in the lower belly (abdomen) is called a retropubic prostatectomy. See also bladder, prostate, prostatectomy, pubic bone.
     Search  [re-VERSE tran-SCRIP-shun puh-LIM-er-ace]
    Often shortened to RT-PCR. A very sensitive test used to find specific cancer-related genetic changes (mutations) in blood, bone marrow, lymph nodes, or other tissue. RT-PCR uses chemical analysis of the ribonucleic acid or RNA (a substance related to DNA [deoxyribonucleic acid]) to look for gene changes. See also bone marrow, deoxyribonucleic acid, lymph node, mutation, ribonucleic acid.
     Search  [RAB-doe-MY-oh-sar-KO-muh]
    Rare type of cancer seen mainly in children and teens that forms in immature skeletal muscle cells. It’s often found in the head and neck, the trunk, or the arms and legs.
    One of a series of 12 pairs of curved bones, some of which connect to the sternum and spine to form the rib cage. The ribs enclose the chest and help protect the heart, lungs, and other organs.
     Search  [RI-bo-noo-KLEE-ick a-sid]
    Often shortened to RNA. A molecule found in all cells that stores and carries genetic messages within the cell. See also deoxyribonucleic acid, messenger RNA.
    Anything that’s related to a person’s chance of getting a disease such as cancer. Some risk factors have a direct role in causing cancer, but in other cases the risk may be due to something else that goes along with the risk factor. For example, COPD (chronic obstructive pulmonary disease) is linked to higher risk of lung cancer, but this is because both can be caused by smoking. Different cancers have different risk factors. For example, excess exposure to sunlight is a risk factor for skin cancer; oral tobacco use is a risk factor for mouth, throat, and other cancers. Some risk factors, such as sun exposure, can be controlled. Others, like a person’s age, can’t be changed. See also gene, mutation.
    See ribonucleic acid.
    See reverse transcription polymerase chain reaction.