I got a scar tissue in lung after radiation therapy for breast cancer. no one told me it could happen. what should i do?

Radiation burns: Radiation therapy causes a type of burn resulting in injury. Hopefully cancer cells are killed, but normal tissue heals with some effects of tissue scarring.

Very rare, but...: ...Well-recognized complication of breast radiation therapy (of course, when you are that "one in a million", that doesn't help). Modern techniques are designed to maximize rx to the breast & minimize effects on the heart and lungs. Your radiation oncologist certainly should have discussed this with you pre-treatment--informed consent is a necessary part of any rx regimen.

Common: To get some scar tissue in the upper part of the lung just below the ribs. This is often best appreciated on a ct scan. Most patients have no change in their breathing function, and the risk of developing a temporary inflammation (pneumonitis) is very low, but treatable with steroids. This risk is probably lower with modern radiation techniques such as imrt.