- Arm I:Patients undergo ultrasound-guided placement of a microwave sensor and a temperature probe (before or after compression of the breast) and external placement of 2 large opposing microwave emitters and up to 7 skin temperature sensors on the compressed breast. Patients then receive focused microwave thermotherapy that slowly heats the primary breast tumor and deep proximal breast tissue. In the absence of undue heating of the skin, a tumor temperature of 48-52° C is targeted and maintained for an equivalent thermal dose of 140-180 minutes.