# 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

xenograft

The cells of one species transplanted to another species.

xeroderma pigmentosum (ZEER-oh-DER-ma pig-men-TOH-sum)

A genetic condition marked by an extreme sensitivity to ultraviolet radiation, including sunlight. People with xeroderma pigmentosum are not able to repair skin damage from the sun and other sources of ultraviolet radiation, and have a very high risk of skin cancer.

xerogram

A picture of the body recorded on paper rather than on film. Also called a xeroradiograph.

xeroradiograph

A picture of the body recorded on paper rather than on film. Also called a xerogram.

xeroradiography (ZEE-ro-ray-dee-AH-gra-fee)

A type of x-ray in which a picture of the body is recorded on paper rather than on film.

xerostomia

Dry mouth. It occurs when the body is not able to make enough saliva.

XK469

A substance that is being studied as a treatment for cancer. It belongs to the family of drugs called topoisomerase II beta inhibitors.

X-linked recessive

X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, will be unaffected.

XR9576

A substance that is being studied for its ability to overcome tumor-cell resistance to anticancer drugs. It belongs to the family of drugs called anthranilic acid derivatives. Also called tariquidar.

x-ray

A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.

x-ray therapy

The use of high-energy radiation from x-rays 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. X-ray therapy is also called radiation therapy, radiotherapy, and irradiation.

XRP9881

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