Radiation oncologist: See oncologist.

Radical (Halsted or standard) mastectomy: See mastectomy.

Radiodense: Effective in blocking x-rays. Breast tissue in younger women is usually more "radiodense" than the fattier tissue in older women. Some contrast agents used in various x-ray procedures are also radiodense. Also called radiopaque.

Radioisotope: Also called isotope. A type of atom that is unstable and prone to break up (decay). Decay releases small fragments of atoms and energy. Exposure to certain radioisotopes can cause cancer. Use of radioisotopes under controlled conditions can be used to treat cancer (see radiotherapy). In certain nuclear medicine imaging procedures, radioisotopes are injected. They travel through the body and collect in areas where the disease is active, showing up as highlighted areas on the images (see nuclear medicine scan). In breast cancer, radioisotopes are used to check for metastasis to the bones.

Radiologic technologist: A health professional (not a physician) trained to properly position patients for x-rays or other radiology studies such as CT or mammography, perform the imaging study, and to develop and check the images for quality. Since mammograms (breast x-rays) are done on a machine that is used only for mammograms, the technologist must have special training in mammography. The films taken by the technologist are sent to a radiologist to be read.

Radiologist: A physician who has taken additional training in interpretation of x-rays and other types of diagnostic imaging studies (for example, mammography, ultrasound, magnetic resonance imaging, computerized axial tomography, etc.)  (See imaging).

Radiopaque: Effective in blocking x-rays. Breast tissue in younger women is usually more "radiopaque" than the fattier tissue in older women. Some contrast agents used in various x-ray procedures are also radiopaque. Also called radiodense.

Radiotherapy/radiation therapy: Treatment with radiation to destroy cancer cells. External sources of radiation used include linear accelerators, cobalt, and betatrons. This type of treatment may be used to reduce the size of a cancer before surgery, or to destroy any remaining cancer cells after surgery. Also called radiation therapy and irradiation.  See also internal radiation or bracytherapy.

Raloxifene: Brand name, Evista. Drug used to prevent and treat osteoporosis.  Raloxifene is also being studied to determine whether it can safely and effectively prevent breast cancer in women at high risk for the disease since it is chemically similar to the drug tamoxifen. 

Reconstruction: See breast reconstruction.

Reconstructive mammoplasty: See mammoplasty, latissimus dorsi flap procedure, and transverse rectus abdominus muscle flap procedure.

Reconstructive surgery: See breast reconstruction.

Rectus abdominus flap procedure: See transverse rectus abdominus muscle flap procedure.

Recurrence: Cancer that returns after treatment. Local recurrence occurs at the same site as the original cancer. Regional recurrence occurs in the lymph nodes near the site of origin. Distant recurrence occurs in organs or tissues further from the original site than the regional lymph nodes (such as the lungs, liver, bone marrow, or brain). The term, metastasis, is used to describe a disease has recurred at another site in the body.

Red blood cells: Cells that supply oxygen to tissues throughout the body.

Reduction mammoplasty: See mammoplasty.

Regimen: A strict, regulated plan (such as diet, exercise, or other activity) designed to reach certain goals. In cancer treatment, a plan to treat cancer.  

Regional involvement: The spread of breast cancer from its original site to nearby areas such as the axillary lymph nodes, but not to distant sites such as other organs.

Rehabilitation: Activities to adjust, heal, and return to a full, productive life after injury or illness. This may involve physical restoration (such as the use of prostheses, exercises, and physical therapy), counseling, and emotional support.

Relapse: Reappearance of cancer after a disease-free period. See recurrence.

Remission: Complete or partial disappearance of the signs and symptoms of cancer in response to treatment; the period during which a disease is under control. A remission may not be a cure.

Residual breast tissue: The remaining glandular breast tissue still in the treated breast following breast-conserving surgery (lumpectomy). 

Revision surgery: A second surgery that may be needed to modify the results of the original breast reconstructive or cosmetic surgery.