Hyperthermia means a body temperature that is higher than normal. High body temperatures are often caused by illnesses, such as fever or heat stroke. But hyperthermia can also refer to heat treatment – the carefully controlled use of heat for medical purposes. Here, we will focus on how heat is used to treat cancer. When cells in the body are exposed to higher than normal temperatures, changes take place inside the cells. Warmer temperatures can make the cells more likely to be affected by other treatments such as radiation therapy or chemotherapy.