NAUTILUS-04: No Axillary Surgical Treatment in Low-Risk Clinically Node-Negative Breast Cancer Without Whole-Breast Radiotherapy (NAUTILUS-04)

The safety of omitting sentinel lymph node biopsy (SLNB) has been established only in patients undergoing breast-conserving surgery with whole-breast radiotherapy, as demonstrated in the prior randomized trials. Whether SLNB can be omitted in patients who will not receive whole-breast radiotherapy remains unknown, despite the parallel expansion of radiotherapy de-escalation in low-risk populations.

NAUTILUS-04 is a prospective, multicenter, randomized, phase III non-inferiority trial evaluating the oncologic safety of SLNB omission in postmenopausal patients with low-risk, clinically node-negative breast cancer who are not planned to receive whole-breast radiotherapy.

Eligible patients are postmenopausal women aged 55 years or older with estrogen receptor-positive, HER2-negative invasive breast cancer, clinical T1-2 and clinically node-negative disease confirmed by physical examination and axillary ultrasound, without neoadjuvant systemic therapy. Patients must be planned for one of three local treatments: breast-conserving surgery without radiotherapy, breast-conserving surgery with accelerated partial breast irradiation, or mastectomy without radiotherapy.

A total of 1,520 patients will be randomized 1:1 to SLNB or no axillary surgery, stratified by planned breast surgery (breast-conserving surgery versus mastectomy) and age (55-64 versus 65 years or older). The primary endpoint is 5-year invasive disease-free survival. Secondary endpoints include 5-year axillary recurrence-free survival, distant recurrence-free survival, overall survival, and quality of life assessed by the EORTC QLQ questionnaire.