[Adjuvant and Neoadjuvant Radiotherapy in Breast Cancer: A Literaure Review and Update on the State of the Evidence in 2020]

Radiation therapy has benefited from many developments over the past 20 years. These developments are mainly linked to the technology, imaging and informatics evolutions which allow better targets definitions, ensure better organs-at-risk sparing and excellent reproducibility of treatments, with a perfect control of patient positioning. In breast cancer radiotherapy, the evolution was marked by the possibility of reducing the duration of treatments from 6-7 to 3-4 weeks by using hypofractionated regimens, or by further reducing the irradiation to one week when treatment is solely focalised to the tumour bed. This concept of accelerated partial breast irradiation has challenged the paradigm of the obligation to irradiate the whole breast after conservative surgery in all patients. In addition, the technical mastery of accelerated partial breast irradiation and the development of stereotactic radiotherapy techniques are currently contributing to the development of research projects in neoadjuvant settings. Thus, numerous ongoing studies are evaluating the impact of high-dose preoperative tumour irradiation, alone or in combination with systemic treatments, on biological tumor changes, on anti-tumour immunity, and on the pathologic complete response, which is considered as predictive of better long-term survival in some molecular breast cancer subtypes. In this review, we discuss all these developments which allow breast radiation therapy to enter the era of personalisation of treatments in oncology.