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# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

R101933

A substance that is being studied for its ability to make cancer cells respond to drugs to which they have become resistant. It belongs to the family of drugs called multidrug resistance inhibitors.

R115777

A substance that is being studied in the treatment of cancer. It inhibits the transformation of normal cells into cancer cells. It belongs to the family of drugs called enzyme inhibitors. Also called tipifarnib.

rabies

A disease of the nervous system caused by the rabies virus. Rabies is marked by an increase in saliva production, abnormal behavior, and eventual paralysis and death.

radiation (ray-dee-AY-shun)

Energy released in the form of particles or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, and medical x-rays.

radiation fibrosis (ray-dee-AY-shun fye-BRO-sis)

The formation of scar tissue as a result of radiation therapy.

radiation nurse

A health professional who specializes in caring for people who are receiving radiation therapy.

radiation oncologist (ray-dee-AY-shun on-KOL-o-jist)

A doctor who specializes in using radiation to treat cancer.

radiation physicist

A person who makes sure that the radiation machine delivers the right amount of radiation to the correct site in the body. The physicist works with the radiation oncologist to choose the treatment schedule and dose that has the best chance of killing the most cancer cells.

radiation surgery

A radiation therapy procedure that uses special equipment to position the patient and precisely deliver a large radiation dose to a tumor and not to normal tissue. This procedure does not use surgery. It is used to treat brain tumors and other brain disorders. It is also being studied in the treatment of other types of cancer, such as lung cancer. Also called radiosurgery, stereotactic external-beam radiation, stereotactic radiation therapy, stereotactic radiosurgery, and stereotaxic radiosurgery.

radiation therapist

A health professional who gives radiation treatment.

radiation therapy (ray-dee-AY-shun THER-ah-pee)

The use of high-energy radiation from x-rays, gamma rays, neutrons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy, implant radiation, or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that circulates throughout the body. Also called radiotherapy.

radical cystectomy (RAD-ih-kal sis-TEK-toe-mee)

Surgery to remove the bladder as well as nearby tissues and organs.

radical hysterectomy (hiss-ter-EK-toe-mee)

Surgery to remove the uterus, cervix, and part of the vagina. The ovaries, fallopian tubes, and nearby lymph nodes may also be removed.

radical lymph node dissection

A surgical procedure to remove most or all of the lymph nodes that drain lymph from the area around a tumor. The lymph nodes are then examined under a microscope to see if cancer cells have spread to them.

radical mastectomy (RAD-ih-kul mas-TEK-toe-mee)

Surgery for breast cancer in which the breast, chest muscles, and all of the lymph nodes under the arm are removed. For many years, this was the breast cancer operation used most often, but it is used rarely now. Doctors consider radical mastectomy only when the tumor has spread to the chest muscles. Also called the Halsted radical mastectomy.

radical nephrectomy (RAD-ih-kul neh-FREK-toe-mee)

Surgery to remove an entire kidney, nearby adrenal gland and lymph nodes, and other surrounding tissue.

radical perineal prostatectomy (RAD-ih-kul peh-rih-NEE-ul prah-stuh-TEK-toh-mee)

Surgery to remove all of the prostate through an incision between the scrotum and the anus. Nearby lymph nodes are sometimes removed through a separate incision in the wall of the abdomen.

radical prostatectomy (RAD-ih-kul prah-stuh-TEK-toe-mee)

Surgery to remove the entire prostate. The two types of radical prostatectomy are retropubic prostatectomy (surgery through an incision in the wall of the abdomen) and perineal prostatectomy (surgery through an incision between the scrotum and the anus).

radical retropubic prostatectomy (RAD-ih-kul reh-troh-PYOO-bik prah-stuh-TEK-toh-mee)

Surgery to remove all of the prostate and nearby lymph nodes through an incision in the wall of the abdomen.

radioactive (RAY-dee-o-AK-tiv)

Giving off radiation.

radioactive drug

A drug containing a radioactive substance that is used in the diagnosis and treatment of cancer and in pain management of bone metastases. Also called a radiopharmaceutical.

radioactive fallout (RAY-dee-o-AK-tiv)

Airborne radioactive particles that fall to the ground during and after an atomic bombing, nuclear weapons test, or nuclear plant accident.

radioactive iodine (RAY-dee-o-AK-tiv EYE-uh-dine)

A radioactive form of iodine, often used for imaging tests or as a treatment for thyroid cancer and certain other cancers. For imaging tests, the patient takes a small dose of radioactive iodine that collects in thyroid cells and certain kinds of tumors and can be detected by a scanner. For treatment of thyroid cancer, the patient takes a large dose of radioactive iodine, which kills thyroid cells. Radioactive iodine is also used in internal radiation therapy for prostate cancer, intraocular (eye) melanoma, and carcinoid tumors. The radioactive iodine is given by infusion or sealed in seeds, which are placed in or near the tumor to kill cancer cells.

radioactive palladium

A radioactive form of palladium (a metallic element that resembles platinum). When used to treat prostate cancer, radioactive seeds (small pellets that contain radioactive palladium) are placed in the prostate. Cancer cells are killed by the energy given off as the radioactive material decays (breaks down).

radioactive seed

A small, radioactive pellet that is placed in or near a tumor. Cancer cells are killed by the energy given off as the radioactive material decays (breaks down).

radiofrequency ablation

The use of electrodes to heat and destroy abnormal tissue.

radioimmunoguided surgery

A procedure that uses radioactive substances to locate tumors so that they can be removed by surgery.

radioimmunotherapy

Treatment with a radioactive substance that is linked to an antibody that will attach to the tumor when injected into the body.

radioisotope

An unstable element that releases radiation as it breaks down. Radioisotopes can be used in imaging tests or as a treatment for cancer.

radiolabeled

Any compound that has been joined with a radioactive substance.

radiologic exam

A test that uses radiation or other imaging procedures to find signs of cancer or other abnormalities.

radiologist (RAY-dee-OL-o-jist)

A doctor who specializes in creating and interpreting pictures of areas inside the body. The pictures are produced with x-rays, sound waves, or other types of energy.

radiology

The use of radiation (such as x-rays) or other imaging technologies (such as ultrasound and magnetic resonance imaging) to diagnose or treat disease.

radionuclide scanning (RAY-dee-oh-NOO-klide)

A test that produces pictures (scans) of internal parts of the body. The person is given an injection or swallows a small amount of radioactive material; a machine called a scanner then measures the radioactivity in certain organs.

radiopharmaceutical

A drug containing a radioactive substance that is used in the diagnosis and treatment of cancer and in pain management of bone metastases. Also called a radioactive drug.

radiosensitization

The use of a drug that makes tumor cells more sensitive to radiation therapy.

radiosensitizer

A drug that makes tumor cells more sensitive to radiation therapy.

radiosurgery

A radiation therapy procedure that uses special equipment to position the patient and precisely deliver a large radiation dose to a tumor and not to normal tissue. This procedure does not use surgery. It is used to treat brain tumors and other brain disorders. It is also being studied in the treatment of other types of cancer, such as lung cancer. Also called radiation surgery, stereotactic external-beam radiation, stereotactic radiation therapy, stereotactic radiosurgery, and stereotaxic radiosurgery.

radiotherapy (RAY-dee-oh-THAYR-uh-pee)

The use of high-energy radiation from x-rays, gamma rays, neutrons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy, implant radiation, or brachytherapy). Systemic radiotherapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that circulates throughout the body. Also called radiation therapy.

radon (RAY-don)

A radioactive gas that is released by uranium, a substance found in soil and rock. Breathing in too much radon can damage lung cells and lead to lung cancer.

raloxifene

A drug that belongs to the family of drugs called selective estrogen receptor modulators (SERMs) and is used in the prevention of osteoporosis in postmenopausal women. Raloxifene is also being studied as a cancer prevention drug.

raltitrexed

An anticancer drug that stops tumor cells from growing by blocking the ability of cells to make DNA. Also called ICI D1694. It belongs to the family of drugs called thymidylate synthase inhibitors.

randomization

When referring to an experiment or clinical trial, the process by which animal or human subjects are assigned by chance to separate groups that compare different treatments or other interventions. Randomization gives each participant an equal chance of being assigned to any of the groups.

randomized clinical trial

A study in which the participants are assigned by chance to separate groups that compare different treatments; neither the researchers nor the participants can choose which group. Using chance to assign people to groups means that the groups will be similar and that the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.

ranpirnase

A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called ribonuclease enzymes. Also called Onconase®.

rapamycin

A drug used to help prevent the body from rejecting organ and bone marrow transplants. It is also being studied as a treatment for cancer. Rapamycin belongs to the family of drugs called immunosuppressants. It is now called sirolimus.

rapid hormone cycling

A procedure in which drugs that block the production of male hormones are alternated with male hormones and/or drugs that promote the production of male hormones. This procedure is being studied in the treatment of prostate cancer.

rapid-onset opioid

An opioid that relieves pain quickly. Opioids are drugs similar to opiates such as morphine and codeine but do not contain and are not made from opium.

ras gene

A gene that has been found to cause cancer when it is altered (mutated). Agents that block its activity may stop the growth of cancer.

ras peptide (rass PEP-tide)

A short piece of the ras protein, which is made by the ras gene. The ras gene has been found to cause cancer when it is mutated (changed).

rasburicase

A drug that is used to treat high blood levels of uric acid in patients receiving treatment for cancer.

rattlesnake root

Cimicifuga racemosa. An eastern North American perennial herb. A substance obtained from the root of the plant has been used in some cultures to treat a number of medical problems. It is being studied in the treatment of hot flashes and other symptoms of menopause. The plant is also called black cohosh, black snakeroot, bugwort, and bugbane.

RAV12

A monoclonal antibody that is being studied in the treatment of some types of cancer. Monoclonal antibodies are made in the laboratory and can locate and bind to cancer cells. It binds to a carbohydrate (sugar) molecule that is found on gastric, colon, pancreatic, prostate, ovarian, breast, and kidney cancer cells.

ravuconazole

A substance that is being studied in the treatment of infections caused by fungi. It belongs to the family of drugs called antifungal agents.

RBC

Red blood cell. A cell that carries oxygen to all parts of the body. Also called erythrocyte.

rebeccamycin

A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called antineoplastic antibiotics.

rebeccamycin analog

A substance that is being studied in the treatment of cancer. It is similar to rebeccamycin. It belongs to the families of drugs called antineoplastic antibiotics and topoisomerase I inhibitors. Also called NSC 655649.

receptor

A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific physiologic effect in the cell.

recombinant

Made through genetic engineering, which is also called gene splicing or recombinant DNA technology. By putting animal or plant genes into the genetic material of bacteria or yeast cells, these microorganisms can be turned into "factories" to make proteins for medical uses.

recombinant tissue plasminogen activator

r-tPA. A protein that is made by the body and that helps dissolve blood clots. It can also be made in the laboratory and is used in the treatment of heart attack and stroke. It is also being studied in the treatment of cancer. r-tPA belongs to the family of drugs called systemic thrombolytic agents. Also called tissue plasminogen activator (tPA), Activase, and Alteplase.

reconstructive surgeon

A doctor who can surgically reshape or rebuild (reconstruct) a part of the body, such as a woman's breast after surgery for breast cancer.

reconstructive surgery

Surgery that is done to reshape or rebuild (reconstruct) a part of the body changed by previous surgery.

rectal

By or having to do with the rectum. The rectum is the last several inches of the large intestine and ends at the anus.

rectum

The last several inches of the large intestine. The rectum ends at the anus.

recur

To occur again.

recurrence

Cancer that has returned after a period of time during which the cancer could not be detected. The cancer may come back to the same place as the original (primary) tumor or to another place in the body. Also called recurrent cancer.

recurrent cancer

Cancer that has returned after a period of time during which the cancer could not be detected. The cancer may come back to the same place as the original (primary) tumor or to another place in the body. Also called recurrence.

red blood cell

RBC. A cell that carries oxygen to all parts of the body. Also called an erythrocyte.

red clover

Trifolium pratense. A plant whose flowers have been used in some cultures to treat certain medical problems. It is being studied in the relief of menopausal symptoms and may have anticancer effects. Also called purple clover and wild clover.

red date

The fruit of the jujube plant. It has been used in some cultures to treat certain medical problems.

red elm

Ulmus fulva or Ulmus rubra. The inner bark of this plant has been used in some cultures to treat certain medical problems. It may have antioxidant effects. Also called slippery elm, gray elm, Indian elm, and sweet elm.

Reed-Sternberg cell

A type of cell that appears in people with Hodgkin's disease. The number of these cells increases as the disease advances.

reflux

The backward flow of liquid from the stomach into the esophagus.

refractory

In medicine, describes a disease or condition that does not respond to treatment.

refractory cancer

Cancer that does not respond to treatment. The cancer may be resistant at the beginning of treatment or it may become resistant during treatment. Also called resistant cancer.

regeneration

In biology, regrowth of damaged or destroyed tissue or body part.

regimen

A treatment plan that specifies the dosage, the schedule, and the duration of treatment.

regional

In oncology, describes the body area right around a tumor.

regional cancer

Refers to cancer that has grown beyond the original (primary) tumor to nearby lymph nodes or organs and tissues.

regional chemotherapy (REE-juh-nul KEE-moh-THAYR-uh-pee)

Treatment with anticancer drugs directed to a specific area of the body.

regional enteritis

Chronic inflammation of the gastrointestinal tract, most commonly the small intestine and colon. Regional enteritis increases the risk for colorectal cancer and small intestine cancer. Also called Crohn's disease.

regional lymph node

In oncology, a lymph node that drains lymph from the region around a tumor.

regional lymph node dissection

A surgical procedure to remove some of the lymph nodes that drain lymph from the area around a tumor. The lymph nodes are then examined under a microscope to see if cancer cells have spread to them.

registered dietitian (...dy-eh-TIH-shun)

A health professional with special training in the use of diet and nutrition to keep the body healthy. A registered dietitian may help the medical team improve the nutritional health of a patient.

regression

A decrease in the size of a tumor or in the extent of cancer in the body.

rehabilitation (REE-huh-BIH-lih-TAY-shun)

In medicine, a process to restore mental and/or physical abilities lost to injury or disease, in order to function in a normal or near-normal way.

rehabilitation specialist

A healthcare professional who helps people recover from an illness or injury and return to daily life. Examples of rehabilitation specialists are physical therapists and occupational therapists.

relapse

The return of signs and symptoms of cancer after a period of improvement.

relative survival rate

A specific measurement of survival. For cancer, the rate is calculated by adjusting the survival rate to remove all causes of death except cancer. The rate is determined at specific time intervals, such as 2 years and 5 years after diagnosis.

relaxation technique

A method used to reduce tension and anxiety, and control pain.

remission

A decrease in or disappearance of signs and symptoms of cancer. In partial remission, some, but not all, signs and symptoms of cancer have disappeared. In complete remission, all signs and symptoms of cancer have disappeared, although cancer still may be in the body.

remission induction therapy

Initial treatment with anticancer drugs to decrease the signs or symptoms of cancer or make them disappear.

remote brachytherapy

A type of internal radiation treatment in which the radioactive source is removed between treatments. Also called high-dose-rate remote brachytherapy or high-dose-rate remote radiation therapy.

renal artery

The main blood vessel that supplies blood to a kidney and its nearby adrenal gland and ureter. There is a renal artery for each kidney.

renal capsule

The fibrous connective tissue that surrounds each kidney.

renal cell cancer

The most common type of kidney cancer. It begins in the lining of the renal tubules in the kidney. The renal tubules filter the blood and produce urine. Also called hypernephroma.

renal collecting tubule

The last part of a long, twisting tube that collects urine from the nephrons (cellular structures in the kidney that filter blood and form urine) and moves it into the renal pelvis and ureters. Also called collecting duct.

renal fascia

A fibrous envelope of tissue that surrounds the kidney. Also called Gerota's fascia and Gerota's capsule.

renal glomerulus

A tiny, round cluster of blood vessels within the kidneys. It filters the blood to reabsorb useful materials and remove waste as urine.

renal pelvis

The area at the center of the kidney. Urine collects here and is funneled into the ureter, the tube that connects the kidney to the bladder.

renal tubular acidosis (REE-nal TOO-bu-lar as-ih-DO-sis)

A rare disorder in which structures in the kidney that filter the blood are impaired, producing urine that is more acid than normal.

replicate

To make a copy or duplicate of something.

replication cycle

In biology, refers to the reproduction cycle of viruses. A repliction cycle begins with the infection of a host cell and ends with the release of mature progeny virus particles.

reproductive cell

An egg or sperm cell. Each mature reproductive cell carries a single set of 23 chromosomes.

reproductive system

In women, this system includes the ovaries, the fallopian tubes, the uterus (womb), the cervix, and the vagina (birth canal). The reproductive system in men includes the prostate, the testes, and the penis.

resectable (ree-SEK-tuh-bul)

Able to be removed by surgery.

resected

Removed by surgery.

resection (ree-SEK-shun)

A procedure that uses surgery to remove tissue or part or all of an organ.

residual disease

Cancer cells that remain after attempts to remove the cancer have been made.

resistant cancer

Cancer that does not respond to treatment. The cancer may be resistant at the beginning of treatment, or it may become resistant during treatment. Also called refractory cancer.

resorption

A process in which a substance, such as tissue, is lost by being destroyed and then absorbed by the body.

respirator (RES-pih-RAY-ter)

In medicine, a machine used to help a patient breathe. Also called ventilator.

respiratory syncytial virus

RSV. A virus that causes respiratory infections with cold-like symptoms.

respiratory system (RES-pih-ra-tor-ee)

The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs. Also called the respiratory tract.

respiratory therapy (RES-pih-ra-tor-ee)

Exercises and treatments that help improve or restore lung function.

respiratory tract

The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs. Also called the respiratory system.

response

In medicine, an improvement related to treatment.

response rate

The percentage of patients whose cancer shrinks or disappears after treatment.

resting

In biology, refers to a cell that is not dividing.

resveratrol

A substance found in the skins of grapes and in certain other plants, fruits, and seeds. It is made by various plants to help defend against invading fungi, stress, injury, infection, and too much sunlight. It is being studied in the prevention of cancer and heart disease. It belongs to the families of drugs called antioxidants and polyphenols.

retina (RET-ih-nuh)

The light-sensitive layers of nerve tissue at the back of the eye that receive images and sends them as electric signals through the optic nerve to the brain.

retinoblastoma

An eye cancer that most often occurs in children younger than 5 years. It occurs in hereditary and nonhereditary (sporadic) forms.

retinoid

Vitamin A or a vitamin A-like compound.

retinol

Vitamin A, a nutrient essential for proper vision and healthy skin and mucous membranes. Retinol is being studied in the prevention of cancer. It belongs to the family of drugs called retinoids.

retinyl palmitate

A drug that is being studied in the prevention of cancer. It belongs to the family of drugs called retinoids.

retroperitoneal (REH-troh-PAYR-ih-toh-NEE-ul)

Having to do with the area outside or behind the peritoneum (the tissue that lines the abdominal wall and covers most of the organs in the abdomen).

retropubic prostatectomy (reh-troh-PYOO-bik prah-stuh-TEK-toh-mee)

Surgery to remove the prostate through an incision made in the wall of the abdomen.

retrospective

Looking back at events that have already taken place.

retrospective cohort study

A research study in which the medical records of groups of individuals who are alike in many ways but differ by a certain characteristic (for example, female nurses who smoke and those who do not smoke) are compared for a particular outcome (such as lung cancer). Also called a historic cohort study.

retrospective study

A study that compares two groups of people: those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). Researchers study the medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition. For example, one group may have been exposed to a particular substance that the other was not. Also called a case-control study.

retroviral vector

RNA from a virus that is used to insert genetic material into cells.

retrovirus

A type of virus that has RNA instead of DNA as its genetic material. It uses an enzyme called reverse transcriptase to become part of the host cells' DNA. This allows many copies of the virus to be made in the host cells. The virus that causes AIDS, the human immunodeficiency virus (HIV), is a type of retrovirus.

RevM10 gene

An antiviral gene that is being studied in the treatment of cancer in patients who have HIV, the virus that causes AIDS.

R-flurbiprofen

A substance that is being studied as a treatment for cancer. It belongs to the family of drugs called nonsteroidal anti-inflammatory drugs (NSAIDs).

rhabdoid tumor

A malignant tumor of either the central nervous system (CNS) or the kidney. Malignant rhabdoid tumors of the CNS often have an abnormality of chromosome 22. These tumors usually occur in children younger than 2 years.

rhabdomyosarcoma

A malignant tumor of muscle tissue.

rheumatism

A group of disorders marked by inflammation or pain in the connective tissue structures of the body. These structures include bone, cartilage, and fat.

rhinoscope

A thin lighted tube used to examine the nose. Also called a nasoscope.

rhinoscopy

A procedure in which a thin, lighted tube is inserted into the nose to look for abnormal areas. Also called nasoscopy.

rhizoxin

A substance that is being studied in the treatment of cancer. It comes from a fungus and is similar to vinca alkaloid drugs. It belongs to the family of drugs called antimitotic agents.

rhubarb

Rheum palmatum or Rheum officinale. The root of this plant has been used in some cultures to treat certain medical problems. It may have anti-inflammatory and anticancer effects. Also called da-huang, Chinese rhubarb, Indian rhubarb, and Turkish rhubarb.

ribavirin

A drug used to treat respiratory syncytial virus (RSV) infection in the lungs.

ribonucleic acid

RNA. One of the two types of nucleic acids found in all cells. The other is deoxyribonucleic acid (DNA). Ribonucleic acid transmits genetic information from DNA to proteins produced by the cell.

ribonucleotide reductase inhibitor

A family of anticancer drugs that interfere with the growth of tumor cells by blocking the formation of deoxyribonucleotides (building blocks of DNA).

rifampin

A drug used in the treatment of infections caused by bacteria. It belongs to the family of drugs called antibiotics.

risedronate (ris-ED-roe-nate)

A substance that is being studied in the prevention and treatment of osteoporosis. It belongs to the family of drugs called bone resorption inhibitors.

risk factor

Something that may increase the chance of developing a disease. Some examples of risk factors for cancer include age, a family history of certain cancers, use of tobacco products, certain eating habits, obesity, lack of exercise, exposure to radiation or other cancer-causing agents, and certain genetic changes.

ritonavir

A drug that belongs to the family of drugs called protease inhibitors. It interferes with the ability of a virus to make copies of itself.

rituximab

A type of monoclonal antibody used in cancer detection or therapy. Monoclonal antibodies are laboratory-produced substances that can locate and bind to cancer cells.

RK-0202

A substance that is being studied in the prevention of oral mucositis in patients receiving radiation therapy or chemotherapy for head and neck cancer.

RMP-7

A substance that is being studied for its ability to help other drugs reach the brain. It belongs to the family of drugs called bradykinin agonists. Also called lobradimil.

RNA

Ribonucleic acid. One of the two types of nucleic acids found in all cells. The other is deoxyribonucleic acid (DNA). RNA transmits genetic information from DNA to proteins produced by the cell.

Ro 31-7453

A substance that is being studied in the treatment of cancer. It may prevent cancer cells from dividing. It belongs to the family of drugs called cell cycle inhibitors.

Ro 50-3821

A substance that is being studied in the treatment of anemia in patients who are receiving chemotherapy. It is a form of erythropoietin (a substance produced in the kidneys that stimulates the production of red blood cells) that has been changed in the laboratory. Also called methoxypolyethylene glycol epoetin beta.

rofecoxib

A drug that was being used for pain relief and was being studied for its ability to prevent cancer and to block the growth of new blood vessels to solid tumors. It belongs to the family of drugs called nonsteroidal anti-inflammatory drugs. Rofecoxib was taken off the market in the U.S. because of safety concerns. Also called Vioxx.

rosiglitazone

A drug taken to help reduce the amount of sugar in the blood. Rosiglitazone helps make insulin more effective and improves regulation of blood sugar. It belongs to the family of drugs called thiazolidinediones.

RPI.4610

A substance that is being studied in the treatment of kidney cancer. It may prevent the growth of blood vessels from surrounding tissue to the tumor. It belongs to the families of drugs called VEGF receptor and angiogenesis inhibitors. Also called Angiozyme.

RPR 109881A

A substance that is being studied in the treatment of cancer. It belongs to the family of drugs called taxanes.

RSR13

A substance that is being studied for its ability to increase the effectiveness of radiation therapy. It belongs to the family of drugs called radiosensitizers. Also called efaproxiral.

RSV

Respiratory syncytial virus. A virus that causes respiratory infections with cold-like symptoms.

r-tPA

Recombinant tissue plasminogen activator. A protein that is made by the body and that helps dissolve blood clots. It can also be made in the laboratory and is used in the treatment of heart attack and stroke. It is also being studied in the treatment of cancer. r-tPA belongs to the family of drugs called systemic thrombolytic agents. Also called tissue plasminogen activator (tPA), Activase, and Alteplase.