A dry scratchiness in your throat and pain when swallowing can make it hard to eat or get a good night's sleep. Usually caused by a cold or the flu, a sore throat also can be a side effect of some breast cancer treatments. The following treatments for breast cancer might cause a sore throat: 1  chemotherapy. 2  radiation therapy. 3  hormonal therapy: 4  Arimidex (chemical name: anastrozole).