External radiation therapy may cause which of the following problems?

External radiation therapy may cause which of the following problems?

• A. Pancytopenia
• B. Leukocytosis
• C. Erythema
• D. Fever

Answer: (C)

External radiation therapy most often causes a local skin reaction called erythema. Radiation damages the rapidly dividing cells in the skin and the superficial blood vessels, triggering an inflammatory response. This leads to dilation of the tiny vessels and increased blood flow to the treated area, producing redness and warmth—the characteristic erythema. It’s dose-dependent and confined to the area being treated, typically appearing after several sessions or within the first couple of weeks.

Pancytopenia would require broad suppression of bone marrow, which is more likely if a large field includes marrow or in high-dose or whole-body irradiation, not usually in a localized external beam treatment. Leukocytosis is not a typical direct effect of localized radiation, and fever is nonspecific and more often related to infection or other causes rather than a direct, common local skin reaction to radiation.