Comparison of Axillary Sentinel Lymph Node Biopsy Versus no Axillary Surgery (INSEMA)

Currently, axillary surgery for breast cancer is considered as staging procedure that does not seem to influence breast cancer mortality, since the risk of developing metastasis depends mainly on the biological behaviour of the primary (seed-and-soil model). Based on this, the postsurgical therapy should be considered on the basis of biologic tumor characteristics rather than nodal involvement.

The goal of the present study is to show that early-stage breast cancer patients with reduced extent of axillary surgery are not inferior regarding disease-free survival outcome compared with the standard arm. All patients will be first randomized to either no axillary surgical intervention or axillary sentinel lymph node biopsy (SLNB). Patients with SLNB and pN+(sn) status will be secondly randomized to either SLNB alone or completion axillary lymph node dissection (ALND) in cases with less than four involved nodes (1-3 macrometastases). Patients with four or more metastatic sentinel lymph nodes should undergo completion ALND.

Postoperative systemic treatment should be based on local multidisciplinary tumor board recommendation according to the current German AGO and S3 guidelines. For women who are treated with breast-conserving surgery, the most common site of local recurrence is the conserved ipsilateral breast itself. Thus, whole-breast radiation therapy after breast-conserving surgery is mandatory and should be performed according to the current guidelines (S3, AGO, DEGRO).

During follow-up, patients will be assessed for disease recurrence according to standard clinical practice. History and physical examination will be performed every 6 months for the first 36 months and yearly thereafter. Annual mammography and sonography will be required; other testing will be based on symptoms and investigator preference. The total number of patients to be randomized into the trial will be approximately 7,095. An event-driven final efficacy analysis will be performed per-protocol for two primary objectives.