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·         P01 Grant   Research Program Project Grant awarded by the National Cancer Institute. This type of grant provides support for a broadly based, multidisciplinary, often long-term research program which has a specific major objective or basic theme. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project.

·         p16 gene   A tumor-suppressor gene which, if lost, permits tumor progression.

·         P30 Grant   Cancer Center Support Grant (CCSG)  awarded by the National Cancer Institute. This type of grant provides support for the necessary shared resources and facilities of Cancer Centers.

·         P50 Grant   Specialized Center Grant awarded by the National Cancer Institute. This type of grant supports research activities focused on a specific disease. They are usually developed in response to a program announcement for a SPORE.

·         p53 gene   A gene that normally inhibits the growth of tumors. This gene is altered (mutated) in many types of cancer.

·         PA-C   Physician’s Assistant, Clinical.

·         PAG   Patient Advocacy Groups.

·         palliative care   [pal´ ee ah tiv]   Therapy with a goal of relieving symptoms and improving quality of life. Also involves offering support and guidance to the patient and family. It does not attempt to alter the course of the disease.

·         palsy   [pawl´ zee]   Paralysis or paresis.

·         papillary craniopharyngioma   [pap´ ih lair ee • kray´ nee o fah rin jee o´ ma]   A type of craniopharyngioma that occurs most commonly in adults and is a usually a solid tumor.

·         papillary ependymoma   [pap´ ih lair ee • ep en dih moe´ ma]   A rare, low grade tumor most commonly located in the cerebellopontine angle.

·         papilledema   [pap il eh dee´ ma]   Swelling of the optic nerve indicating increased intracranial pressure. Also called choked disc.

·         paralysis   [pah ral´ ih sis]   Loss of muscle function so the person is unable to move all or part of their body. Can be caused by injury or a disease of the nervous system.

·         parasagittal   [pear ah saj´ ih tul]   Parallel to the midline, sagittal (front to back) plane.

·         parasellar   [pear ah sell´ ur]   Around or near the sellar region.

·         parenteral   [pah ren´ tur al]   Something that bypasses the intestines; to give medicines through a vein or artery, into a muscle, through the skin, etc.

·         paresis   [pah ree´ sis]   Weakness, partial paralysis.

·         paresthesia   [pear es thee´ ze ah]   Abnormal sensations, such as tingling, burning or prickling.

·         parietal lobe   [pah rye´ ih tal]   One of four lobes of the cerebral hemisphere, behind the frontal lobe, processing touch and spatial organization.

·         partial response   The shrinking, but not complete disappearance, of a tumor in response to therapy. Also called partial remission.

·         partial seizure    A seizure affecting one part of a cerebral hemisphere. Symptoms depend on the part involved. There are two types: simple partial and complex partial. Also called a focal seizure.

·         pathologist   A physician trained in the nature, cause, process and effects of disease. Using a microscope, they examine samples of tissue removed during surgery to determine an exact diagnosis.

·         pathway   A chain of interconnected neurons. Neural pathways are also called tracts. Can also refer to treatment pathways which are guidelines for treating specific diseases such as those developed by medical institutions, health insurance companies and others.

·         PBTC   Pediatric Brain Tumor Consortium, an NCI funded clinical cooperative group organized to evaluate new treatments for pediatric brain tumor patients.

·         PCL   Primary CNS Lymphoma   [lim foe´ ma]   A brain tumor arising from cells of the lymphatic system.

·         PCV   Procarbazine + CCNU + Vincristine. A combination chemotherapy regimen.

·         PDQ   Physician Data Query. A dynamic database that lists ongoing clinical trials sponsored by the National Cancer Institute and others. Can be accessed by calling the Cancer Information Service at 1-800-422-6237.

·         PDR   Physician’s Desk Reference. A compilation of prescription drug product information provided by the products’ manufacturers and widely distributed by the publisher to all physicians in the US. Can also by purchased by consumers wherever medical reference books are sold.

·         PDT   See Photodynamic Radiation Therapy.

·         Peacock System   Brand name of a method used to conform the radiation beams used in 3D-CRT and IMRT.

·         pediatric   [pee dee at´ rik]   Pertains to children.

·         perimetry   [peh rim´ eh tree]   A diagnostic test that measures the size of visual fields.

·         peripheral neuropathy   [peh rif´ uh ral • nur op´ ah thee]  A general term that refers to changes in sensation or function in the peripheral nervous system. Common symptoms include weakness; numbness; burning, tickling, prickling or tingling sensations; or pain in the arms, legs, hands and feet. There are numerous causes.

·         Peripheral Nervous System   [peh rif´ uh ral]   The nervous system outside the Central Nervous System, consisting of nerves and ganglia.

·         permeable   [pur´ me ah bul]   Allows substances to pass through. The blood brain barrier is selectively permeable, allowing only certain substances to enter the brain from the blood vessels.

·         PET scan   Positron Emission Tomography. A scanning device which uses low-dose radioactive glucose to measure brain activity.

·         petechia   [peh tee´ kee ah]   Pinpoint size, flat, round red spots under the skin caused by bleeding.

·         petit mal seizure   [pe tee´ • mall]   A type of generalized seizure that causes an impairment of consciousness. Also called absence seizure.

·         PFS   Progression Free Survival. The patient is alive and the tumor is stable — not growing or shrinking.

·         phagocytes   [fag´ o sitez]   Large white blood cells that contribute to immune defenses by swallowing up (ingesting) microbes or other cells and foreign particles much like scavengers or garbage collectors.

·         pharmacist   A professional trained in preparing and dispensing medicines.

·         pharmacopoeia   [far ma ko pea´ ah]   An official book containing a list of medications, their formulas, and standards for their strength. In the United States, the book is abbreviated USP (for Pharmacopoeia of the USA).

·         Phase I Clinical Trial   Designed to find out how much of a new substance can safely be given and the best way to give it. A small number of patients (15-25)  with various kinds of tumors receive the experimental treatment.

·         Phase I/II Clinical Trial   If the drug under investigation is well known in other diseases, but the correct dosage with brain tumors is not yet determined, phases I and II may be combined.

·         Phase II Clinical Trial   Designed to determine the effectiveness of a new treatment using pre-defined criteria. Phase II treatments are offered to patients with specific types of tumors. The study stays open until the entry of about 20-50 patients with each type of tumor to be tested. An effective therapeutic treatment is one in which patients’ tumors stop growing or shrink in size. Clinical trials may also include quality of life criteria.

·         Phase III Clinical Trial   Designed to compare the new, experimental treatment to standard treatment to determine which is more effective. Typically, several hundred patients
are enrolled in a Phase III trial.

·         Phase IV Clinical Trial   After a treatment has been approved by the Food and Drug Administration (FDA), a phase IV trial might be needed to evaluate side effects that were not apparent in the phase III trial or to answer unresolved questions. Very large numbers of people are enrolled in this type of trial.

·         PhD   Doctor of Philosophy degree.

·         PHN   Public Health Nurse.


·         phosphorylation [FOS-for-ih-lay-shun]  A molecular energy process through which a phosphate group is added to a molecule, such as a sugar or a protein.


·         photodynamic radiation therapy   [foe toe dye nam´ ik]   Combines the use of a sensitizing drug and laser surgery. A light sensitive drug is given through a vein and concentrates in the tumor. During surgery, tumor cells containing the drug appear fluorescent. The physician aims a laser at those cells, which activates the drug. The activated drug then kills the tumor cells. Only operable tumors can be treated with this procedure. Commonly abbreviated PDT.


·         photofrin   [foe´ toe frin]   A drug used in photodynamic radiation therapy that is absorbed by tumor cells. When exposed to light, it is activated to kill the cancer cells in which it has concentrated.

·         photon   [foe´ tonn]   A kind of ionizing radiation. It consists of x-rays (light energy) created by a linear accelerator or gamma rays emitted by radioactive isotopes (e.g., cobalt).

·         photosensitizer   A drug used in photodynamic radiation therapy that is capable of concentrating in tumor cells and is activated by laser light. Photofrin is one such drug.

·         PHRMA   Pharmaceutical Research and Manufacturers of America. A trade organization of US pharmaceutical companies. Maintains a website containing several publications that might be of interest to patients and their families.

·         plieocytosis [PLEE-oh sy-toh-sis]   An abnormal increase in cell count, such as the white blood cell count in a bodily fluid such as cerebrospinal fluid which may indicate infection or inflammation.

·         physiatrist   [fizz eye´ ah tryst]   A physician trained in rehabilitative medicine.

·         physical therapist   A professional trained to assist people in restoring muscle function. Commonly abbreviated PT.

·         physician’s assistant   An individual qualified by academic and clinical education to provide patient services in a variety of settings under the supervision and direction of a licensed physician. Commonly abbreviated PA.

·         PI   Principal Investigator.

·         pia mater   [pee´ ah • mott´ ur]   The innermost layer of the meninges; the thin membrane covering and in direct contact with the brain and spinal cord.

·         pilocytic astrocytoma   [pie low sit´ ik • as tro sigh toe´ ma]   A low grade astrocytoma that occurs mainly in children and is generally the most benign of the astrocytomas. Many optic gliomas and cerebellar astrocytoma are pilocytic astrocytomas.

·         pilot study   The initial, small study examining a new method or treatment. Treatment administered to a small group of patients to learn if it will be effective and safe before offering it to a larger group.

·         pineal gland   [pine´ eel]   Located below the corpus callosum, this gland secretes the hormone melatonin which controls biological rhythms.

·         pineal tumors   [pine´ eel]   Pineal tumors represent fewer than 1% of all primary brain tumors. However, 3% to 8% of childhood brain tumors occur in this area. These tumors include germinomas, teratomas and other germ cell tumors, the pineocytoma, pineoblastoma and mixed pineal tumors, as well as astrocytomas. Mixed pineal tumors contain a mixture of cell types.

·         pineoblastoma   [pine´ ee o blas toe´ ma]   Pineoblastoma is an aggressive, high grade pineal tumor.

·         pineocytoma   [pine´ ee o sigh toe´ ma]   The pineocytoma is generally a slow-growing, pineal tumor.

·         pituitary carcinoma   [pih two´ ih tare ee • kar sin o´ ma]   The rare, aggressive form of pituitary adenoma. It is diagnosed only when there are proven metastases.

·         pituitary gland   [pih two´ ih tare ee]   A bean sized organ lying just behind the bridge of the nose at the base of the brain, it consists of two lobes: the anterior (adenohypophysis) and the posterior (neurohypophysis). The pituitary is connected to the hypothalamus by a stalk. The “master” endocrine gland, the pituitary secretes several very important hormones. Also called the hypophysis.

·         pituitary tumors   [pih two´ ih tare ee]   These are almost always benign, slow growing adenomas and represent about 15% of all primary brain tumors. Pituitary adenomas occur at any age but are rare before puberty. These tumors might be classified by the symptoms they cause; by the hormone they secrete, if any; or by their size or appearance. Microadenomas are less than 10mm in size, larger tumors are called macroadenomas, and can threaten vision by compressing on the optic nerves and chiasm.

·         placebo   [pluh see´ boe]   An inactive substance. A harmless substance that has no biological effect.

·         placebo study   [pluh see´ boe]   A clinical trial that has an inactive substance as one of its treatment arms. This type of study is rare for brain tumors.

·         PLAP   placental alkaline phosphatase. A germ cell tumor marker found in the cerebrospinal fluid and blood.

·         plasma   [plas´ ma]   The clear, yellowish, fluid portion of the blood in which cells are suspended.

·         plasma cells   [plas´ ma]   Large antibody-producing cells that develop from B cells. Part of the immune system.

·         plasticity   The capability of being shaped or changed or having a function altered.

·         platelets   [plait´ letz]   Granule-containing cell fragments circulating in the blood that help prevent bleeding by causing blood clots to form. Also called thromobocytes.

·         pleomorphic xanthoastrocytoma    [plea o more´ fik • zan´ tho as tro sigh toe´ ma]   An astrocytoma that most frequently occurs in the temporal lobe of children and young adults.

·         pluripotent   A stem cell capable of maturing into almost any type of body cell.

·         PNET   Primitive Neuroectodermal Tumor. PNET is a name used for tumors which appear identical under the microscope to the medulloblastoma, but occur primarily in the cerebrum. PNETs are most common in very young children.

·         PNP   Pediatric Nurse Practitioner.

·         POG   Pediatric Oncology Group. An NCI funded clinical cooperative group organized to evaluate new treatments in pediatric cancer patients. POG, the Children’s Cancer Group (CCG) and two other pediatric cancer groups have merged to form the Children’s Oncology Group (COG).

·         polymer wafer implants   During surgery, bio-degradable wafers soaked with a chemotherapy drug are placed into the cavity left by the tumor’s removal. Gliadel is the proprietary name the wafer.

·         pons   [ponz]   The part of the brain stem between the medulla oblongata and the midbrain, POS   Point Of Service. A health maintenance organization (HMO) type of managed care health insurance plan that allows you to use doctors and hospitals outside the plan for an additional cost.

·         postictal   [post ick´ tal]   After a seizure.

·         posterior   [pos tier´ ee or]   The rear.

·         posterior fossa   [pos tier´ ee or • foss´ • ah]   The posterior fossa is a shallow hollow of the occipital bone in which the cerebellum and fourth ventricle are located. Also called the infratentorium.

·         potentiate   [po ten´ she ate]   To make more effective.

·         PPO   Preferred Provider Organization. A managed care health insurance plan in which you use doctors, hospitals and providers that belong to a specific network. You can use doctors, hospitals and providers outside the network for an additional cost.

·         PR   Partial Response. Refers to a tumor that has stopped growing or shrunk only minimally in size. Full response means the tumor has disappeared completely.

·         premotor area   The region of the frontal lobe in front of the primary motor area.

·         prevalence   [prev´ ah lens]   The number of people in a given country currently surviving with a specific disease.

·         PRG   Progress Review Group. A cancer-specific planning process designed to complement the science-based planning process of the National Cancer Institute.

·         primary auditory area   [aw´ dih tore ee]   The area of the temporal lobe involved with hearing.

·         primary brain tumor   Original source of tumor is the brain rather than other areas of the body.

·         primary CNS lymphoma   [lim foe´ ma]   A brain tumor that arose from cells of the lymphatic system. Commonly abbreviated PCL.

·         primary motor area   The area of the frontal lobe involved with voluntary movement. It is located just forward of the parietal lobe and the central fissure.

·         primary somesthetic area   [so´ mess thet ik]   The area of the parietal lobe involved with sensation. It is located just back of the frontal lobe and the central fissure.

·         primary therapy   The initial treatment.

·         primary tumor   The original tumor.

·         primitive neuroectodermal tumor   The name used for a tumor which appears under the microscope to be identical to a medulloblastoma, but is not located in the cerebellum. These tumors are most common in very young children. Abbreviated PNET.

·         primitive   Undeveloped or in early stages of development, undifferentiated.

·         probability  A measure of how likely it is that some event will occur; a number expressing the ratio of favorable cases to the whole number of cases possible


·         progenitor: [pro JEN i tur]  In cell biology, a parent cell that gives rise to a distinct cell lineage by a series of cell divisions.

·         prognosis   [prog no´ sis]   A forecast as to likely outcome, the chance of recovery. Abbreviated PX.

·         progressive disease   A disease that is increasing in severity.

·         proliferate   [pro lif´ uh rate]   To grow by cell reproduction.

·         promoter [pro·MO·ter]   A segment of DNA which controls the production of cell by-products. The word also refers to a substance or product created by the cell which is capable of promoting the rapid reproduction of mutated cells.

·         prophylactic   [pro fih lak´ tic]   Preventative. Also called prophylaxis.

·         proprioception   [pro pree o sep´ shun]   The sense of body position. Information from nerve endings in muscles, tendons and joints enables people to determine the position of their body parts and where to move them.

·         proteins   [pro´ teenz]   Substances composed of long sequences of amino acids. Proteins are the major component of all cells and are involved in structure, hormones, enzymes, muscle contraction, the immune system and essential life functions.

·         proteomics   [pro tea ahm´ iks]   Analysis using information technology (bioinformatics) to categorize the identity, quantity, structure, size, character, and function of the proteins in blood and tissue samples in health and disease. The results of these studies can influence future drug discovery and development.

·         proto-oncogenes   [pro´ toe ong´ koe jeans]   Genes that normally control cell growth and repair but are capable of becoming oncogenes.

·         protocol   [pro´ toe kol]   A written outline of care for a clinical trial. The plan states what will be done in the study and why. It outlines how many people will take part, what types of patients may take part, what tests they will receive and how often, and the treatment schedule.

·         proton beam radiosurgery   A cyclotron is an adapted nuclear reactor that produces charged particle beams of protons. These beams are used for small, deep-seated tumors such as a pituitary tumor. Also called heavy particle radiation therapy.

·         proximal   [prock´ sih mal]   Located closest to the reference point.

·         pseudotumor cerebri   [sou´ doe too´ mor • ser ee´ bry]   Increased pressure in the brain for reasons unknown. Pseudotumor cerebri literally means “false brain tumor.” It is most common in women between the ages of 20 and 50. Also called benign intracranial hypertension.

·         pseudomargins [SUEDO margin]   In histochemical staining, a condition where dye delineates a false margin. The cancer may actually extend beyond this dyed pseudomargin to a real margin.


·         pseudoprogression [SUE DO pro greh shun]  Radiographic worsening of disease, seen on scans, which is caused by treatment rather than the disease itself.  Pseudoprogression is sometimes thought to be tumor growth, but may actually be changes in tissue caused by the treatment. This is not uncommon in tumors treated with a combination of radiation and chemotherapy.

·         PsyD   Doctor of Psychology degree.

·         PT   Physical Therapist. An professional trained to assist people in restoring muscle function.

·         PTOG   Proton Therapy Oncology Group, an NCI funded clinical cooperative group organized to evaluate the use of proton beam therapy for treating adult cancer patients.

·        ptosis  [toe´ sis]   Drooping of the upper eyelid.

·         PTV   Planning Tumor Volume. A term used in planning diation therapy, it is the area to be irradiated including the tumor and (usually) a small additional area surrounding it.

·         PubMed   A system provided by the US National Library of Medicine to search MEDLINE, the computerized database of medical articles, references and abstracts.

·         pulmonary   [pull’ mon air ee]   Refers to the lungs.