SNAC-2 is a trial comparing two operations for detecting cancer cells in the lymph nodes of women with early breast cancer.

The two operations are:

  • axillary clearance
  • sentinel node biopsy.

You can find out more about these two techniques on our surgery page.

The status of the axillary or armpit lymph nodes remains the most important indicator of outcome for women with breast cancer and helps predict the need for further treatment (e.g. chemo or radiotherapy).

Traditionally, axillary node status has been determined by removal of most of the nodes (axillary clearance or dissection).  This operation may lead to arm swelling (lymphoedema), pain, some abnormal skin sensation or shoulder stiffness. 

An earlier study through the Royal Australasian College of Surgeons called the “Sentinel Node biopsy versus Axillary Clearance or SNAC 1 trial” has already established that for women with small single (unifocal) breast cancers, the surgical removal of the “sentinel” nodes (i.e. the first lymph node/s draining from the region of the breast cancer) provides accurate information as to whether axillary nodes are involved with cancer or not.

In these women sentinel node based management (SNBM) resulted in fewer side effects than axillary clearance. However with sentinel node biopsy, there is a small false negative rate (5.5. %) i.e. a risk of not removing a lymph node with cancer spread.  There is also a small risk for developing lymphoedema.

A second phase of sentinel node biopsy research in New Zealand and Australia, called the SNAC 2 trial, seeks to evaluate the long term cancer outcomes of this technique and in particular whether sentinel node biopsy is safe for women with larger or multi focal tumours and cancers of more aggressive biological type.

This is a very important trial because very few women with larger tumours and none with multi focal tumours have been included in other international randomised trials of SNBM.

Follow-up of participants in SNAC 2 trial was completed in January 2023 and the results are currently being analysed (May 2023).