IORT is a new form of partial breast irradiation in women with early breast cancer. An increased radiation-dosage is applied to the wound cavity during the operation. IORT is used/tested either in combination with the (conventional) post-operative percutaneous radiation therapy/RT with the aim to shorten the overall duration of RT or as a one-time only boost-therapy with the aim to substitute conventional RT at all and to reduce the overall radiation dosage.