A Phase I Dose-escalation Trial of Definitive Single Dose Stereotactic Body Radiotherapy in Low-risk Breast Cancer Patients: DESERT I Trial

Radiotherapy (RT) is a fundamental pillar in the fight against cancer. In the case of breast cancer, RT has traditionally been applied as an adjuvant treatment following surgery. However, in recent years, there has been research into the potential benefit of administering RT prior to surgery in a neoadjuvant manner. Given that these studies have shown promising results, it is logical to think that certain patients could benefit from exclusive RT treatment, thereby avoiding surgery and its possible sequelae. This study is a phase I dose-escalation clinical trial with sequential assignment, open-label, in which five different doses (20Gy, 23Gy, 26Gy, 28Gy, and 30Gy) will be tested on the tumor using stereotactic body radiotherapy (SBRT) technique. The aim of the study is to determine the maximum tolerated dose (MTD) based on acute toxicity, which will allow us to proceed with a phase II clinical trial to confirm efficacy and assess the late toxicity of the treatment. Secondary objectives include assessing the pathological response via core needle biopsy (CNB), radiological response, quality of life, and cosmesis. Additionally, molecular studies will be conducted on tissue and through liquid biopsy; pre- and post-treatment, we aim to identify mutations and predictors of response.