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- Oat cell lung cancerAnother name for small cell lung cancer. Called this because the cells look oat shaped under the microscope.
- Occult tumourAn occult tumour is one that is hidden or can't be found. Sometimes this is called an unknown primary tumour. The place where a cancer begins is called the primary cancer. If a secondary cancer is found in the body, but the doctors don't know where the cancer started, they call it an unknown(...)
- Occupational therapistA person trained to help people with any sort of disability to manage day to day activities (for example, dressing, cooking etc).
- OctreoscanThis is a special type of scan for rare cancers called neuroendocrine tumours (NETs). You have an injection of a very small amount of radioactive material (a radioactive isotope) into a vein in your arm. Then you wait for this to circulate throughout your body and attach to the NET cells. Once(...)
- Octreotide (Sandostatin)Inhibits the release of hormones in the pancreas and gut which results in a reduction in gut secretions. It is used in the treatment of carcinoid syndrome, vasoactive intestinal peptide tumours and malignant bowel obstruction.
- Ocular melanoma (eye melanoma)Melanoma that has started in the eye. This is very rare. It behaves differently depending on where in the eye it started and how advanced it is when it is diagnosed. It can begin in the iris, the ciliary body, the choroid, the conjunctiva, or the eyelid. Treatment depends on stage and type of(...)
- Oesophagectomy Surgery to remove part or most of the oesophagus (gullet).
- OesophagogastrectomyAn operation to remove the stomach and part of the gullet (oesophagus).
- Oesophagus (foodpipe)The tube that carries food from the mouth to the stomach.
- OestrogenOne of the two female sex hormones.
- Oestrogen receptor negativeMeans that no oestrogen receptors have been found on the cancer cells. This may affect the treatment given.
- Oestrogen receptor (oestrogen receptors)The area on the surface of a cancer cell that is triggered by oestrogen. The area on the cell surface is like a lock and oestrogen is the key that fits and turns the lock.
- Oestrogen receptor positiveMeans that oestrogen receptors have been found on the cancer cells. This may affect the treatment given.
- OligodendrogliomaA type of brain tumour. Glioma which develops from cells called oligodendrocytes.
- Omega 3 unsaturated fatty acidType of fat found in oily fish. This fat may help to reduce the risk of breast and bowel cancer when included in the diet. This may be because of some effect of this acid. Or it may be because people who have a high fish intake eat less meat. Research is ongoing.
- Oncogene (oncogenes)Literally means 'cancer gene'. A gene that has become abnormal and tells its cell to multiply continuously.
- OncologistA doctor who specialises in treating cancer.
- Open clinical trialsOpen means the trial is currently recruiting participants.
- Open radical cholecystectomyAn operation to remove the gall bladder, some nearby liver tissue and all the lymph nodes near and around the gall bladder. This operation is also known as an extended cholecystectomy
- OpioidA strong, painkilling drug that is similar to endorphins. The body makes endorphins in response to pain. Opioid drugs were originally made from opium poppies and can now be man made in the laboratory. Types of opioid include morphine, fentanyl, diamorphine and codeine.
- Oral (orally)Taken by mouth. Used to refer to medicines taken as tablets, capsules or liquid.
- OrchidectomyAn operation to remove a testicle.
- Organ rejectionAfter an organ transplant (for example, kidney or heart transplant) people have to take drugs to stop their body rejecting the new organ. These drugs suppress their immune systems and this can make them more at risk of some other diseases, such as non-Hodgkin's lymphoma.
- Orphan drugsOrphan drug products are drugs, vaccines or in vivo diagnostic agents which physicians use to treat, prevent or diagnose rare diseases. Usually the drugs are not commercially viable. Pharmaceutical companies often do not develop and market such products because the financial return is small(...)
- OsteochondromaA type of benign bone disease (not a cancer).
- OsteoporosisLoss of calcium from the bones, making them weaker. Sometimes called bone thinning.
- OsteosarcomaA type of primary bone cancer.
- OutpatientA patient who attends the hospital or clinic for an appointment or treatment without staying overnight.
- Ovarian ablationUsing chemotherapy or radiotherapy to stop a woman's ovaries from working. This stops the ovaries making sex hormones and is useful in treating cancers which use sex hormones to grow (for example, breast cancer). Causes an early menopause.
- Ovarian cancerCancer of the ovaries.
- Ovarian removalSurgery to take out the ovaries. Also called oophorectomy or ovariectomy. This stops the production of sex hormones and is useful in treating cancers which use sex hormones to grow (for example, breast cancer). Causes an early menopause.
- Ovary (ovaries)Part of a woman's reproductive system. There are two ovaries and they lie on either side of the womb in women. They produce eggs and the female sex hormones, oestrogen and progesterone.
- Overall survivalThe percentage of people are alive, with or without cancer, after a specified number of years from the onset of illness (usually 5 years).
- Overview (overviews)Similar to meta-analyses. Putting together the results of more than one trial.
- OVX1A protein (marker) produced by some women with ovarian cancer.
- Oxaliplatin (Eloxatin)A chemotherapy drug used in the treatment of carcinoma of the colon and rectum.