An energy radiation applicator apparatus for hyperthermic treatment of targeted tissue in a patient is provided. The apparatus comprises a catheter for insertion into the patient, and an applicator operatively attached to the catheter and an energy source sufficient for elevating the temperature of targeted tissue in proximity to the applicator to a preselected temperature and for maintaining the preselected temperature during treatment. It may also comprise a positioning mechanism operatively attached to the catheter so that the applicator may be positioned at a desired position in proximity to the targeted tissue to be treated, a temperature sensor operatively attached to the catheter and in operative association with the applicator for measuring the temperature of the targeted tissue, and a locator for determining whether the applicator remains at the desired position. The locator is operatively attached to the energy source and deactivates the energy source when the conditions exist that permit the applicator to move from the desired position.