Which of the following is NOT a common side effect associated with radiation therapy?

Weight gain is not typically associated with radiation therapy as a common side effect. Radiation therapy often targets cancerous tissues, which can lead to inflammation and tissue damage, potentially resulting in symptoms such as nausea and vomiting, diarrhea, and skin erythema.

Nausea and vomiting can occur due to the effects of radiation on abdominal organs, while diarrhea may arise, particularly when radiation is directed at the abdominal or pelvic areas, affecting the gastrointestinal tract. Skin erythema, or redness of the skin, is a well-known reaction at the site where radiation is applied, due to the damage caused to skin cells.

In contrast, weight gain is not a usual side effect of radiation therapy. Instead, patients may experience weight loss due to side effects like nausea, changes in appetite, or alterations in metabolism. Thus, identifying weight gain as not being a common side effect highlights the distinction between typical reactions to radiation therapy and those that are less frequently observed.