Tumor Bed Boost Radiotherapy in the Conservative Treatment of Breast Cancer: A Review of Intra-Operative Techniques and Outcomes

SIMPLE SUMMARY: Radiation therapy is an important part of conservative breast cancer treatment. Boost radiation of the tumor bed at enough doses is often necessary to increase local control of the disease. There are several techniques for administering a boost, including intraoperative radiotherapy. This review presents the main published results of the use of an intraoperative boost with electrons and low-energy X-ray for local control, secondary effects and tolerance, as well as the advantages in specific situations such as neo-adjuvant therapy or in combination with reconstructive surgery procedures. ABSTRACT: Conservative surgery is the preferred treatment in the management of breast cancer followed by adjuvant whole-breast irradiation. Since the tumor bed is the main site of relapse, boost doses are conveniently administered according to risk factors for local relapse to increase the efficacy of the treatment. The benefit of a radiation boost is well established and it can be performed by several techniques like brachytherapy, external radiation or intraoperative radiotherapy. Greater precision in localizing the tumor cavity, immediacy and increased biological response are the main advantages of intraoperative boost irradiation. This modality of treatment can be performed by means of mobile electron accelerators or low-photon X-ray devices. There is a lot of research and some published series analyzing the results of the use of an intraoperative boost as an adjuvant treatment, after neoadjuvant systemic therapy and in combination with some reconstructive surgeries. This review discusses advantages of intraoperative radiotherapy and presents the main results of a boost in terms of local control, survival, tolerance and cosmesis.