Feasibility of Tailoring Axillary Surgery Based on the Molecular Subtype and Nodal Burden of Breast Cancer Patients- SentiOMIT and SentiMACRO Trial

The treatment and prognosis of breast cancer (BC) are dependent on its molecular subtype and nodal burden. In early BCs with favourable molecular subtype, the incidence of axillary node involvement is low. However, these patients are still subjected to an axillary operation, which can result in additional cost, operating time and morbidities. Similarly, in patients with limited nodal burden of 1-2 metastatic nodes, there is emerging evidence that these patients may need sentinel lymph node biopsy (SLNB) only, instead of an axillary clearance (AC), which has more surgical morbidities.

We aimed to determine if axillary surgery could be safely tailored in BC patients based on their molecular subtype and nodal burden, without compromising their oncological outcomes. This could in turn reduce the morbidities associated with the axillary surgery,

Total 350 patients will be enrolled. 50 patients with early BC and favourable molecular subtype will be enrolled in a pilot study A (SentiOMIT), whereby SLNB is omitted. For eligible patients who declined study A and other stage I-II patients, with preoperative N0 status, undergoing upfront surgery but did not meet the inclusion criteria of Study A, these patients will be enrolled into study B (SentiMACRO) to undergo SLNB.

In study B, the patients will be categorized based on SLNB into 3 groups with 100 patients in each arm: B1 with pN0, B2- 1-2 metastatic nodes and B3- >/=3 metastatic nodes. In Study B, we aim to investigate if the B2 group (100 patients) can be treated with a less invasive procedure of SLNB alone instead of AC, without affecting oncological outcomes. B1 and B3 are controls.

The outcomes for study A and B include short term outcomes such as morbidity rates, cost and operating time savings. Long term outcomes include recurrence and survival rates. This study will allow individualisation of axillary surgery based on the patient's molecular subtype and nodal burden, to benefit patients' care.