IMNI PRECISION trial protocol: a phase II, open-label, non-inferior randomized controlled trial of tailoring omission of internal mammary node irradiation for early-stage breast cancer

Background: Since the publication of MA-20 and EORTC-22922 trials, chest wall (CW)/ whole breast (WB) irradiation + comprehensive regional nodal irradiation (RNI) with internal mammary node irradiation (IMNI) has been the standard adjuvant treatment for early-stage breast cancer (BC). However, one size does not fit all BC, and the risk of recurrence significantly varies among this patient population. In addition, whether all BC patients presented with one to three positive lymph nodes (pN1) could benefit from IMNI remains controversial. Thus, the optimal adjuvant RNI volume for early-stage BC with T1-2N1 remains undetermined. Methods: The IMNI PRECISION trial is a single institute, open-labeled, non-inferior, randomized controlled trial. A total of 214 clinically high risk BC patients which is characterized as having at least two of the five clinically adverse factors (age <= 40, three positive LN, T2 stage, grade 3 and Ki-67 index >= 14%), but genomic score low risk (the genomic score <= 44) N1 breast cancers are randomly assigned to omitting IMNI group (experimental group) or with IMNI (control group) with a 1:1 ratio. The primary endpoint of this trial is event-free survival, and secondary endpoints include overall survival and locoregional recurrence-free survival. Discussion: The IMNI PRECISION design allows promising clinical-genomic model to stratify the individualized risk of developing recurrence and guides the optimal RNI treatment for early-stage (pT1-2N1) BC patients. We anticipate that our results would provide high-level evidence to tailor IMNI according to individualized recurrence risk of BC.

Automated summary

The IMNI PRECISION trial aims to determine the optimal adjuvant radiation therapy for early-stage breast cancer patients with positive lymph nodes (T1-2N1). The study randomly assigns patients with high clinical risk but low genomic risk to receive either comprehensive regional nodal irradiation with internal mammary node irradiation or to omit the internal mammary node irradiation. The primary endpoint is event-free survival.