Glossary of Cancer Terms
O(6)-benzylguanine A drug that may improve the response of cancer cells to chemotherapy.
oat cell cancer An aggressive (fast-growing) cancer that usually forms in tissues of the lung and spreads to other parts of the body. The cancer cells look small and oval-shaped when looked at under a microscope. Also called small cell lung cancer.
obese Having an abnormally high, unhealthy amount of body fat.
objective improvement An improvement that can be measured by the health care provider (for example, when a tumor shrinks or there are fewer cancer cells in the blood).
objective response A measurable response.
oblimersen A substance that is being studied in the treatment of cancer. It may kill cancer cells by blocking the production of a protein that makes cancer cells live longer and by making them more sensitive to anticancer drugs. It belongs to the family of drugs called antisense oligodeoxyribonucleotides. Also called Genasense, augmerosen and bcl-2 antisense oligodeoxynucleotide G3139.
observation Closely monitoring a patient's condition but withholding treatment until symptoms appear or change. Also called watchful waiting.
observational study A type of study in which individuals are observed or certain outcomes are measured. No attempt is made to affect the outcome (for example, no treatment is given).
obsessive-compulsive disorder An anxiety disorder in which a person has intrusive ideas, thoughts or images that occur repeatedly, and in which he or she feels driven to perform certain behaviors over and over again. For example, a person may worry all the time about germs and so will wash his or her hands over and over again. Having an obsessive-compulsive disorder may cause a person to have trouble carrying out daily activities.
obstruction Blockage of a passageway.
obtundation A dulled or reduced level of alertness or consciousness.
occult primary tumor Cancer in which the site of the primary (original) tumor cannot be found. Most metastases from occult primary tumors are found in the head and neck.
occult stage non-small cell lung cancer Cancer cells are found in sputum (mucus coughed up from the lungs), but no tumor can be found in the lung by imaging or bronchoscopy, or the primary tumor is too small to be assessed.
occupational therapist A health professional trained to help people who are ill or disabled learn to manage their daily activities.
octreotide A drug similar to the naturally occurring growth hormone inhibitor somatostatin. Octreotide is used to treat diarrhea and flushing associated with certain types of tumors.
octreotide scan A type of radionuclide scan used to find carcinoid and other types of tumors. Radioactive octreotide, a drug similar to somatostatin, is injected into a vein and travels through the bloodstream. The radioactive octreotide attaches to tumor cells that have receptors for somatostatin. A radiation-measuring device detects the radioactive octreotide, and makes pictures showing where the tumor cells are in the body. Also called somatostatin receptor scintigraphy and SRS.
ocular melanoma A rare cancer of melanocytes (cells that produce the pigment melanin) found in the eye. Also called intraocular melanoma.
odor A smell.
odorant A substance that gives off a smell.
off-label Describes the legal use of a prescription drug to treat a disease or condition for which the drug has not been approved by the US Food and Drug Administration.
ofloxacin An antibiotic drug used to treat infection. It belongs to the family of drugs called quinolone antibiotics.
OGF Opioid growth factor. A substance made by the body and in the laboratory. It is being studied in the treatment of cancer. It is a type of angiogenesis inhibitor and biological response modifier. Also called opioid growth factor.
OGX-011 A substance that is being studied as a treatment for cancer. It belongs to the family of drugs called antisense oligonucleotides.
ointment A substance used on the skin to soothe or heal wounds, burns, rashes, scrapes or other skin problems. Also called unguent.
olfaction The sense of smell.
olfactory Having to do with the sense of smell.
olfactory system The parts of the body involved in sensing smell, including the nose and many parts of the brain. Smell may affect emotion, behavior, memory and thought.
olfactory transduction A series of events in which cells in the nose bind to scent-bearing molecules and send electrical signals to the brain where they are perceived as smells.
oligoastrocytoma A rare type of brain tumor made up of two kinds of cells, oligodendrocytes and astrocytes, which are brain cells that nourish and support nerve cells. Also called mixed glioma.
oligodendroglial tumor A rare, slow-growing tumor that begins in the oligodendrocytes (brain cells that nourish and support nerve cells). Also called an oligodendroglioma.
oligodendroglioma A rare, slow-growing tumor that begins in the oligodendrocytes (brain cells that nourish and support nerve cells). Also called an oligodendroglial tumor.
oligofructose-enriched inulin A substance that is used to improve digestive system and bone health and is being studied in the prevention of colon cancer. Oligofructose-enriched inulin is made by combining two starches, oligofructose and inulin. These substances occur naturally in many plants, including chicory root, wheat, bananas, onion and garlic. Oligofructose-enriched inulin helps healthy bacteria grow in the intestines and helps the body absorb calcium and magnesium. Also called Raftilose Synergy 1.
oltipraz A drug used in cancer prevention.
omega-3 fatty acid A type of fat obtained in the diet and involved in immunity.
omentectomy Surgery to remove part or all of the omentum.
omentum A fold of the peritoneum (the thin tissue that lines the abdomen) that surrounds the stomach and other organs in the abdomen.
omeprazole A drug that inhibits gastric acid secretion.
Ommaya reservoir A device surgically placed under the scalp and used to deliver anticancer drugs to the fluid surrounding the brain and spinal cord.
Oncaspar A form of the drug asparaginase that is used together with other anticancer drugs to treat acute lymphoblastic leukemia (ALL). It belongs to the family of drugs called enzymes. Also called pegaspargase and PEG-asparaginase.
oncogene A gene that normally directs cell growth. If altered, an oncogene can promote or allow the uncontrolled growth of cancer. Alterations can be inherited or caused by an environmental exposure to carcinogens.
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.
oncology The study of cancer.
oncology nurse A nurse who specializes in treating and caring for people who have cancer.
oncology pharmacy specialist A person who works with an oncologist to prepare anticancer drugs.
oncolysate An extract made from cancer cells that are infected with a lytic strain of virus. The extract contains both cancer cell proteins and virus proteins. Oncolysates are being studied as cancer vaccines.
oncolysis The breakdown, or lysis, of a tumor. This can occur by mechanical means, chemicals, or infectious agents such as viruses. Oncolytic viruses do not lyse most normal cells.
oncolytic virotherapy Treatment using a virus that has been changed in the laboratory to find and destroy cancer cells without harming healthy cells. It is a type of targeted therapy. Also called virotherapy and viral therapy.
Onconase® A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called ribonuclease enzymes. Also called ranpirnase.
Oncophage A vaccine made from a patient's tumor cells that may help the body’s immune system find and kill cancer cells. This vaccine is being studied in the treatment of melanoma, kidney cancer, brain tumors and other types of cancer. It belongs to the family of drugs called biological therapies. Also called gp96 heat shock protein-peptide complex vaccine or gp96 HSP-peptide complex.
ondansetron A drug that is used to prevent or reduce nausea and vomiting caused by chemotherapy and radiation therapy for cancer. It belongs to the family of drugs called antiemetics. Also called Zofran.
onset of action The length of time it takes for a medicine to start to work.
Ontak A substance used to treat cutaneous T-cell lymphoma when other treatments have not worked. It is also being studied in the treatment of chronic lymphocytic leukemia that has not responded to treatment. It belongs to the family of drugs called biological therapy agents. Also called denileukin diftitox.
ONYX-015 A modified cold virus that selectively grows in and destroys certain types of cancer cells and leaves normal cells undamaged.
oophorectomy Surgery to remove one or both ovaries.
open biopsy A procedure in which a surgical incision (cut) is made through the skin to expose and remove tissues. The biopsy tissue is examined under a microscope by a pathologist. An open biopsy may be done in the doctor’s office or in the hospital, and may use local anesthesia or general anesthesia. A lumpectomy to remove a breast tumor is a type of open biopsy.
open colectomy An operation to remove all or part of the colon through a long incision made in the wall of the abdomen. When only part of the colon is removed, it is called a partial colectomy.
open label study A type of study in which both the health providers and the patients are aware of the drug or treatment being given.
operable Describes a condition that can be treated by surgery.
ophthalmic Having to do with the eye.
ophthalmoscope A lighted instrument used to examine the inside of the eye, including the retina and the optic nerve.
opiate A drug used to treat pain. It contains opium or a substance made from opium (such as morphine).
opioid A drug used to treat moderate to severe pain. Opioids are similar to opiates such as morphine and codeine, but they do not contain and are not made from opium.
opioid growth factor OGF. A substance made by the body and in the laboratory. It is being studied in the treatment of cancer. It is a type of angiogenesis inhibitor and biological response modifier. Also called OGF.
opportunistic infection An infection caused by an organism that does not normally cause disease. Opportunistic infections occur in people with weakened immune systems.
oprelvekin A type of biological response modifier (a substance that can improve the body's natural response to infection and disease) that stimulates immune response and may reduce toxicity to the gastrointestinal system resulting from cancer therapy. These substances are normally produced by the body. They are also made in the laboratory for use in treating cancer and other diseases. Also called interleukin-11 and IL-11.
optic nerve The nerve that carries messages from the retina to the brain.
oral By or having to do with the mouth.
oral and maxillofacial surgeon A dentist who specializes in surgery of the mouth, face, and jaw.
oral cancer Cancer that forms in tissues of the lip or mouth. This includes the front two thirds of the tongue, the upper and lower gums, the lining inside the cheeks and lips, the bottom of the mouth under the tongue, the bony top of the mouth, and the small area behind the wisdom teeth.
oral cavity The mouth.
oral contraceptive pill A pill used to prevent pregnancy. It contains hormones that block the release of eggs from the ovaries. Most oral contraceptives include estrogen and progestin. Also called birth control pill.
oral surgeon A dentist with special training in surgery of the mouth and jaw.
orchidectomy Surgery to remove one or both testicles. Also called orchiectomy.
orchiectomy Surgery to remove one or both testicles. Also called orchidectomy.
oregovomab A monoclonal antibody that is being studied in the treatment of ovarian cancer. Monoclonal antibodies are made in the laboratory and can locate and bind to cancer cells. Oregovomab binds to the CA-125 antigen, which is found on most ovarian cancer cells. Also called OvaRex.
organ A part of the body that performs a specific function. For example, the heart is an organ.
organism A living thing, such as an animal, a plant, a bacterium or a fungus.
Oriental medicine A medical system that has been used for thousands of years to prevent, diagnose and treat disease. It is based on the belief that qi (the body's vital energy) flows along 20 meridians (channels) throughout the body and keeps a person’s spiritual, emotional, mental, and physical health in balance. Oriental medicine aims to restore the body’s balance and harmony between the natural opposing forces of yin and yang, which can block qi and cause disease. Oriental medicine includes acupuncture, diet, herbal therapy, meditation, physical exercise and massage. Also called traditional Chinese medicine and TCM.
oropharyngeal cancer Cancer that forms in tissues of the oropharynx (the part of the throat at the back of the mouth, including the soft palate, the base of the tongue, and the tonsils). Most oropharyngeal cancers are squamous cell carcinomas (cancer that begins in flat cells lining the oropharynx).
oropharynx The part of the throat at the back of the mouth. It includes the soft palate, the base of the tongue, and the tonsils.
orthodox medicine A system in which medical doctors and other healthcare professionals (such as nurses, pharmacists and therapists) treat symptoms and diseases using drugs, radiation, or surgery. Also called conventional medicine, Western medicine, mainstream medicine, biomedicine and allopathic medicine.
OSI-774 A drug used to treat certain types of non-small cell lung cancer. It is also used together with gemcitabine to treat pancreatic cancer and is being studied in the treatment of other types of cancer. OSI-774 belongs to the family of drugs called epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. Also called erlotinib, erlotinib hydrochloride, CP-358774 and Tarceva.
OSI-7904L A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called thymidylate synthase inhibitors.
osmolality The concentration of particles dissolved in a fluid. The osmolality of serum can help diagnose several medical conditions such as dehydration, diabetes and shock.
osmotic Having to do with osmosis (the passage of a liquid through a membrane from a less concentrated solution to a more concentrated one). This causes the more concentrated solution to become diluted, and makes the concentrations in both solutions more equal. Osmotic also refers to a type of laxative that increases the amount of water in the large intestine, which softens the stool to help it pass more easily.
osteitis deformans A chronic condition in which both the breakdown and regrowth of bone are increased. Osteitis deformans occurs most frequently in the pelvic and leg bones, skull, and lower spine. It is most common in older individuals, and may lead to bone pain, deformities, and fractures. Also called Paget's disease of bone.
osteogenic sarcoma A cancer of the bone that usually affects the large bones of the arm or leg. It occurs most commonly in young people and affects more males than females. Also called osteosarcoma.
osteolytic Causing the breakdown of bone.
osteomyelitis Inflammation of the bone caused by an infection, which may spread to the bone marrow and tissues near the bone. Osteomyelitis can cause severe pain in the infected bone. If it is not treated, it can kill bone tissue.
osteoporosis A condition that is marked by a decrease in bone mass and density, causing bones to become fragile.
osteosarcoma A cancer of the bone that usually affects the large bones of the arm or leg. It occurs most commonly in young people and affects more males than females. Also called osteogenic sarcoma.
ostomy An operation to create an opening (a stoma) from an area inside the body to the outside. Colostomy and urostomy are types of ostomies.
OTC Over-the-counter. A medicine that can be bought without a prescription (doctor's order). Examples include analgesics (pain relievers) such as aspirin and acetaminophen. Also called nonprescription.
OTI-010 A preparation of laboratory-treated human mesenchymal stem cells that is being studied for its ability to prevent or decrease graft-versus-host disease in patients having stem cell transplants.
otolaryngologist A doctor who specializes in treating diseases of the ear, nose, and throat. Also called ENT doctor.
ounce A measure of weight (one-sixteenth pound) and volume (one-eighth cup).
outcome A specific result or effect that can be measured. Examples of outcomes include decreased pain, reduced tumor size and improvement of disease.
outpatient A patient who visits a health care facility for diagnosis or treatment without spending the night. Sometimes called a day patient.
OvaRex A monoclonal antibody that is being studied in the treatment of ovarian cancer. Monoclonal antibodies are made in the laboratory and can locate and bind to cancer cells. OvaRex binds to the CA-125 antigen, which is found on most ovarian cancer cells. Also called oregovomab.
ovarian Having to do with the ovaries, the female reproductive glands in which the ova (eggs) are formed. The ovaries are located in the pelvis, one on each side of the uterus.
ovarian ablation Surgery, radiation therapy or a drug treatment to stop the functioning of the ovaries. Also called ovarian suppression.
ovarian borderline malignant tumor A condition in which cells that may become cancer form in the thin layer of tissue that covers an ovary (female reproductive gland in which eggs are made). In this condition, tumor cells rarely spread outside of the ovary. Also called ovarian low malignant potential tumor.
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).
ovarian epithelial cancer Cancer that occurs in the cells on the surface of the ovary. Also called epithelial ovarian cancer.
ovarian germ cell tumor An abnormal mass of tissue that forms in germ (egg) cells in the ovary (female reproductive gland in which the eggs are formed). These tumors usually occur in teenage girls or young women, usually affect just one ovary, and can be benign (not cancer) or malignant (cancer). The most common ovarian germ cell tumor is called dysgerminoma.
ovarian low malignant potential tumor A condition in which cells that may become cancer form in the thin layer of tissue that covers an ovary (female reproductive gland in which eggs are made). In this condition, tumor cells rarely spread outside of the ovary. Also called ovarian borderline malignant tumor.
ovarian suppression Surgery, radiation therapy, or a drug treatment to stop the functioning of the ovaries. Also called ovarian ablation.
ovary One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.
over-the-counter OTC. A medicine that can be bought without a prescription (doctor's order). Examples include analgesics (pain relievers) such as aspirin and acetaminophen. Also called nonprescription.
overactive thyroid Too much thyroid hormone. Symptoms include weight loss, chest pain, cramps, diarrhea and nervousness. Also called hyperthyroidism.
overall survival The percentage of subjects in a study who have survived for a defined period of time. Usually reported as time since diagnosis or treatment. Also called the survival rate.
overdose An amount of drug that is more than what should be taken at one time.
overexpress In biology, to make too many copies of a protein or other substance. Overexpression of certain proteins or other substances may play a role in cancer development.
overgrowth syndrome A group of genetic disorders in which there is an abnormal increase in the size of the body or a body part that is often noted at birth. Examples of overgrowth syndromes include neurofibromatosis, Sotos syndrome, Beckwith-Wiedemann syndrome, Simpson-Golabi-Behmel syndrome, Weaver syndrome, Proteus syndrome, Sturge-Weber syndrome and fragile X syndrome. Many of these syndromes increase the risk of cancer.
overweight Being too heavy for one’s height. Excess body weight can come from fat, muscle, bone and/or water retention. Being overweight does not always mean being obese.
ovulation The release of an egg from an ovary during the menstrual cycle.
oxaliplatin A drug used to treat colorectal cancer that is advanced or has come back. It is also being studied in the treatment of other types of cancer. Oxaliplatin belongs to the family of drugs called platinum compounds. Also called Eloxatin.
oxandrolone A drug used to help patients gain weight after injury, chronic infection or severe illness. It belongs to the family of drugs called anabolic steroids.
OXi-104 An anticancer drug being evaluated in combination with cisplatin.
oxidation Process in which molecules are split to give products that have unpaired electrons.
oxidative metabolism A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also called aerobic respiration, cell respiration and aerobic metabolism.
oxidative stress A condition in which antioxidant levels are lower than normal. Antioxidant levels are usually measured in blood plasma.
oxide A type of chemical substance that is a combination of oxygen and another substance. Oxides are found in essential oils.
oxycodone A morphine-like drug used to treat medium to severe pain. It belongs to the family of drugs called opioid analgesics and may be habit-forming.
oxygen A colorless, odorless gas. It is needed for animal and plant life. Oxygen that is breathed in enters the blood from the lungs and travels to the tissues.
oxygen saturation test A test that measures the amount of oxygen being carried by red blood cells. One method uses a device that shines light through a finger. The device measures the amount of oxygen in the blood based on the way red blood cells carrying oxygen absorb and reflect light. In another method blood is taken from an artery and the amount of oxygen is measured directly. An oxygen level that is lower than normal may be a sign of lung disease or other medical conditions.
oxygen therapy Treatment in which a storage tank of oxygen or a machine called a compressor is used to give oxygen to people with breathing problems. It may be given through a nose tube, a mask, or a tent. The extra oxygen is breathed in along with normal air. Also called supplemental oxygen therapy.