Research over the past 20 years continues to answer questions about reducing treatment to the axilla

20 May 2020

The status of the axillary or armpit lymph nodes remains the most important indicator of outcome for women diagnosed with breast cancer, and helps predict the need for further treatment (e.g. chemo or radiotherapy). Traditionally, axillary node status has been determined by the removal of all of the nodes (called axillary clearance or axillary node dissection).  This operation may lead to arm swelling (lymphoedema), pain, some abnormal skin sensation, and shoulder stiffness.  Over the past 20 years the WBCRT has enabled the introduction of a reduced surgery to the armpit called “sentinel node biopsy”. Sentinel node biopsy involves surgical removal of the lymph nodes most closely related to the breast cancer (usually 2-3 lymph nodes).

Since 2001, Waikato Breast Surgeons and researchers have participated in a learning phase of sentinel node biopsy, followed by four international clinical trials introducing sentinel node biopsy surgery for different types of breast cancer.

The sentinel node biopsy trials have been part of the journey of reducing the amount of breast cancer surgery. In the 1970s it was believed that all women with breast cancer needed a mastectomy, and nowadays most women don’t need a mastectomy, and breast-conserving surgery is performed in a majority of cases. Prior to the early 2000s, all women underwent axillary clearance.

The most recent sentinel node trial is the “ POsitive Sentinel NOde: adjuvant therapy alone versus adjuvant therapy plus Clearance or axillary radiotherapy” or “POSNOC” trial. This is a UK led international trial, which is coordinated in Australia and New Zealand by Breast Cancer Trials ANZ.

At the moment, it is usual for women with a small amount of cancer spread to 1 or 2 sentinel lymph nodes to have further treatment (axillary clearance or axillary radiotherapy). The POSNOC clinical trial is investigating whether some of these women may be able to avoid treatment to the armpit, and, as a result, avoid the side effects of this treatment as well as how this treatment affects a woman’s quality of life.

It is currently believed that women with more than a tiny amount of cancer in the sentinel node need to have the other lymph nodes removed (axillary clearance). This may or may not be true, and this is the question that the POSNOC clinical trial will answer. Very often there is no cancer seen in the other armpit lymph nodes when removed. So those women get the short and long term side effects of the axillary treatment for no benefit.

We now know that additional therapies (e.g. hormonal therapy and chemotherapy) are very good at preventing the cancer from coming back, so additional treatment to the axilla (armpit) may no longer be needed. Previous research suggests that axillary treatment may not change the risk of the cancer coming back in the armpit or anywhere else. However, more research is needed to give a clear answer.

If we can prove that less axillary treatment is just as safe as doing more treatment, this will be a great outcome for women diagnosed in the future.

Recruitment for this UK led trial is planned to complete in mid-2021. We acknowledge the Waikato and other NZ women who have had the courage to participate in this trial.