Glossary

O(6)-benzylguanine
A drug that may improve the response of cancer cells to chemotherapy.
ob/gyn
A branch of medicine that specializes in the care of women during pregnancy and childbirth and in the diagnosis and treatment of diseases of the female reproductive organs. It also specializes in other women’s health issues, such as menopause, hormone problems, contraception (birth control), and infertility. Also called obstetrics and gynecology.
obatoclax
A substance being studied in the treatment of several types of cancer. Obatoclax blocks the actions of certain proteins that cells need to live and it may kill cancer cells. It is a type of apoptosis inducer, a BCL2 protein antagonist, and a BH3 mimetic.
obatoclax mesylate
A substance being studied in the treatment of several types of cancer. It is a form of obatoclax, which blocks the activity of certain proteins needed for cells to live and may cause tumor cells to die. It is a type of apoptosis inducer.
obese
Having an abnormally high, unhealthy amount of body fat.
obesity
A condition marked by an abnormally high, unhealthy amount of body fat.
obinutuzumab
A drug used with another drug to treat chronic lymphocytic leukemia (CLL) that has not already been treated. It is also being studied in the treatment of other types of cancer. Obinutuzumab binds to a protein called CD20, which is found on B cells (a type of white blood cell) and some types of leukemia cells. This may help the immune system kill cancer cells. Obinutuzumab is a type of monoclonal antibody. Also called Gazyva.
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 sodium
A substance 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 is a type of antisense oligodeoxyribonucleotide. Also called augmerosen, bcl-2 antisense oligodeoxynucleotide G3139, and Genasense.
observation
In medicine, watching a patient’s condition but not giving treatment unless symptoms appear or change.
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.
obstetrician
A doctor who specializes in caring for women during pregnancy and childbirth. Obstetricians also care for the fetus (unborn baby), treat problems with pregnancy, and deliver babies.
obstetrics and gynecology
A branch of medicine that specializes in the care of women during pregnancy and childbirth and in the diagnosis and treatment of diseases of the female reproductive organs. It also specializes in other women’s health issues, such as menopause, hormone problems, contraception (birth control), and infertility. Also called ob/gyn.
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 tests or bronchoscopy, or the tumor is too small to be checked.
occupational therapist
A health professional trained to help people who are ill or disabled learn to manage their daily activities.
OCT
A procedure that uses infrared light waves to give three-dimensional (3-D) pictures of structures inside tissues and organs. The pictures are made by a computer linked to the light source. Also called optical coherence tomography.
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.
odds ratio
A measure of the odds of an event happening in one group compared to the odds of the same event happening in another group. In cancer research, odds ratios are most often used in case-control (backward looking) studies to find out if being exposed to a certain substance or other factor increases the risk of cancer. For example, researchers may study a group of individuals with cancer (cases) and another group without cancer (controls) to see how many people in each group were exposed to a certain substance or factor. They calculate the odds of exposure in both groups and then compare the odds. An odds ratio of one means that both groups had the same odds of exposure and, therefore, the exposure probably does not increase the risk of cancer. An odds ratio of greater than one means that the exposure may increase the risk of cancer, and an odds ratio of less than one means that the exposure may reduce the risk of cancer. Also called relative odds.
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