R115777: An anticancer drug that inhibits the transformation of normal cells to cancer cells. It belongs to the family of drugs called enzyme inhibitors.

radiation fibrosis (ray-dee-AY-shun fye-BRO-sis): The formation of scar tissue as a result of radiation therapy.

radiation oncologist (ray-dee-AY-shun on-KOL-o-jist): A doctor who specializes in using radiation to treat cancer.

radiation surgery: A radiation therapy technique that delivers radiation directly to the tumor while sparing the healthy tissue. Also called radiosurgery and stereotactic external beam irradiation.

radiation therapy (ray-dee-AY-shun): 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 in the area 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 mastectomy (RAD-ih-kal 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 operation most used, but it is used now only when the tumor has spread to the chest muscles. Also called the Halsted radical mastectomy.

radical prostatectomy (RAD-ih-kalpros-ta-TEK-toe-mee): Surgery to remove the entire prostate. The two types of radical prostatectomy are retropubic prostatectomy and perineal prostatectomy.

radioactive (RAY-dee-o-AK-tiv): Giving off radiation.

radioactive iodine: A radioactive form of the chemical element iodine, often used for imaging tests or as a treatment for cancer.

radiofrequency ablation: The use of electrical current to destroy tissue.

radioimmunoguided surgery: A procedure that uses radiolabeled substances to detect tumors for surgical removal.

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.

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: 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.

radiopharmaceuticals: Drugs containing a radioactive substance that are used in the diagnosis and treatment of cancer and in pain management of bone metastases. Also called radioactive drugs.

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

radiosensitizers: Drugs that make tumor cells more sensitive to radiation.

radiotherapy (RAY-dee-o-THER-a-pee): The use of high-energy radiation from x-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 from materials called radioisotopes. Radioisotopes produce radiation and can be placed in or near the tumor or in the area near cancer cells. This type of radiation treatment is called internal radiation therapy, implant radiation, interstitial radiation, or brachytherapy. Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that circulates throughout the body. Radiotherapy is also called radiation therapy, irradiation, and x-ray therapy.

radon (RAY-don): A radioactive gas that is released by uranium, a substance found in soil and rock. When too much radon is breathed in, it 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 inhibits tumor cells from multiplying by interfering with cells' ability to make DNA. Also called ICI D1694.

randomized: Describes an experiment or clinical trial in which animal or human subjects are assigned by chance to separate groups that compare different treatments.

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.

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. A ras peptide is a protein fragment produced by the ras gene.

rebeccamycin: An anticancer drug that belongs to the family of drugs called antineoplastic antibiotics.

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.

rectal: By or having to do with the rectum. The rectum is the last 8 to 10 inches of the large intestine and ends at the anus.

rectum: The last 8 to 10 inches of the large intestine.

recur: To occur again. Recurrence is the return of cancer, at the same site as the original (primary) tumor or in another location, after the tumor had disappeared.

recurrence: The return of cancer, at the same site as the original (primary) tumor or in another location, after the tumor had disappeared.

recurrent cancer: Cancer that has returned, at the same site as the original (primary) tumor or in another location, after the tumor had disappeared.

red blood cells: RBCs. Cells that carry oxygen to all parts of the body. Also called erythrocytes.

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

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 term used when liquid backs up into the esophagus from the stomach.

refractory cancer: Cancer that has not responded to treatment.

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 (kee-mo-THER-a-pee): Treatment with anticancer drugs that is directed to a specific area.

regional enteritis: Inflammation of the intestines, but usually only of the small intestine. Also called Crohn's disease.

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

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

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

relative survival rate: A specific measurement of survival. In 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.

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 there still may be cancer in the body.

remission induction therapy: The initial chemotherapy a person receives to bring about a remission.

renal capsule: The fibrous connective tissue that surrounds each kidney.

renal cell cancer: Cancer that develops in the lining of the renal tubules, which filter the blood and produce 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 using that is more acid than normal.

reproductive cells: Egg and sperm cells. 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.

resected: Surgical removal of part of an organ.

resection (ree-SEK-shun): Removal of tissue or part or all of an organ by surgery.

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

resistance: Failure of a cancer to shrink after treatment.

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.

respiratory therapy (RES-pih-ra-tor-ee): Exercises and treatments that help improve or restore lung function.

response: In medicine, an improvement related to treatment.

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

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. It is essential for proper vision and healthy skin and mucous membranes. Retinol is being studied for cancer prevention; it belongs to the family of drugs called retinoids.

retinyl palmitate: A drug being studied in cancer prevention; it belongs to the family of drugs called retinoids.

retroperitoneal (RET-row-PAIR-ih-toe-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 (re-tro-PYOO-bik pros-ta-TEK-toe-mee): Surgery to remove the prostate through an incision made in the abdominal wall.

retrospective: Looking back at events that have already taken place.

retrospective study: A study that looks backward in time, usually using medical records and interviews with patients who already have or had a disease.

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

RevM10 gene: An antiviral gene being studied for treatment of cancer in patients who have HIV, the virus that causes AIDS.

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.

rhizoxin: An anticancer drug isolated from a fungus. It is similar to the family of drugs called vinca alkaloids.

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

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

risk factor: A habit, trait, condition, or genetic alteration that increases a person's chance of developing a disease.

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.

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 cells. The other is DNA (deoxyribonucleic acid). RNA plays a role in sending information from DNA to the protein-forming system of the cell.

Ro 31-7453: An anticancer drug that may prevent cancer cells from dividing.

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.

RPR 109881A: A drug that belongs to the family of anticancer drugs called taxanes.

RSR13: A drug that may increase the effectiveness of radiation therapy.