The T-REX trial: Tailored regional radiotherapy using gene expression profiling in clinically node- negative breast cancer patients with 1-2 sentinel node macrometastases

In this multicenter, prospective randomized trial, clinically node-negative breast cancer patients with 1-2 macrometastases in their sentinel lymph node (SLN) biopsy, and an estrogen receptor positive, HER2-negative primary tumor will be enrolled. In the standard arm all patients will receive locoregional RT to the breast/thoracic wall and regional lymph nodes. In the intervention arm no lymph node RT will be given. All patients will receive RT to the remaining breast after breast conserving surgery, while mastectomy patients in the intervention arm will not receive any RT.
Primary outcome is recurrence free survival after five years which for non-inferiority should not worsen the outcome in the intervention arm more than 4.5 percentage units compared with the standard arm. Secondary outcomes include locoregional recurrence, overall survival, arm morbidity, and health-related quality of life. Translational studies on tumor biology in relation to risk of recurrence and benefit of RT, will be performed for all patients providing consent for biobanking.
Registration number at clinicaltrials.gov is NCT05634889. The trial aims to include 1350 patients over the period March 2023 to December 2028 in Sweden, Norway and Finland.