Clinical Database of Safe Personalized Adjuvant Breast Radiotherapy Based on Individual Radiosensitivity

Severe but also moderate toxicities after curative-intent radiotherapy (RT), such as a poor cosmetic outcome following breast cancer can have a negative impact on quality of life and a marked effect on subsequent psychological outcome. Nevertheless, current practice standards commonly prescribe radiation dose and volume without regard to individual radiosensitivity. In that context, a normal tissue radiosensitivity test that includes a rapid (72 h) radiosensitivity assay based on flow cytometric assessment of radiation-induced CD8 T-lymphocyte apoptosis (RILA) and other significant clinical parameters (multifactorial nomogram) was developed. Omission of radiotherapy has been suggested when luminal A tumor subtype is combined with clinical and pathologic factors defining a subgroup of patients with a low risk of ipsilateral breast recurrence. In this group, the benefits of radiotherapy are small \[6\]. Reduction of the breast irradiated volume is also a possibility that has been tested and published using IORT, brachytherapy or external beam radiotherapy. Hypofractionation has been adapted to breast cancer radiotherapy. Overall, all recent clinical trials \[13, 14\] showed only few late effects when hypofractionation was delivered to the whole breast (WB). These results reinforce the need of patients' selection using the NovaGray Breast® test. Our hypothesis is therefore that the different techniques (volume reduction or hypofractionation) as well as radiotherapy omission will significantly reduce grade ≥2 bf+ in a personalized approach (driven by a predictive assay of late effects) compared to WB hypofractionation in a selected population at low risk of breast recurrence. We would like to establish a prospective evaluation of daily practice including the individual radiosensitivity test to the decision of daily practice