What are the most common side effects of radiation therapy that patients get?

Depends on technique: Classic radiation is given via external beams to whole breast over 6-7 weeks with primarily local affect like mild repeated sunburn (redness, irritation-more extreme may incl. Blistering or peeling). Newer techniques if a larger daily dose cn be given can reduce the time to 3-4 weeks. Other option is accelerated partial breast usually w/implanted device and seeds over 5 days.

Varies: Radiation affects different body parts in different ways. Early stage breast cancer relatively few symptoms - typically some fatigue, sometimes a mild sunburn like skin irritation in the radiated areas. Base of the tongue, much harsher side effects (and it is often combined with chemotherapy). They all get severe dry mouth, and may be unable to eat for awhile. Ask your rad onc doc for specifics.