Management of the draining axillary lymph nodes in breast cancer has thankfully come a long way since the Halsted radical mastectomy. While it is still vital to stage the axilla, as it remains a critical component of prognosis, there is an ongoing trend for surgical de-escalation.
This is preferable for the patient where possible as traditional axillary dissection/clearance has several significant co-morbid complications including seroma, lymphoedema, chronic pain, axillary paraesthesia and shoulder dysfunction.
Axillary lymph node dissection (ALND) was de-escalated to four node axillary sampling in the 1990s and subsequently sentinel node biopsy (SLNB) became standard.
SLNB involves injecting a radioactive tracer and/or a blue dye into the lymphatics draining the breast so that the first, ‘sentinel’ lymph nodes of the axilla can be identified. If these nodes are negative, the likelihood of further axillary disease is low.
Multiple studies demonstrated a high SLN identification rate, low false negative rates and no difference in overall survival, disease free survival and locoregional recurrence in those omitting ALND. Morbidity associated with SLNB is significantly less than in full ALND.
Initially, SLNB was often accompanied by intra-operative node assessment to allow for completion of ALND at the same operation. Given the number of treatment options for a positive sentinel node, there has been a move towards allowing discussion at MDT with full histopathology.
Axillary radiation has been shown to have good control with fewer complications than dissection in low-volume disease, and for certain patients with limited nodal disease ALND or nodal radiation may not be warranted. The results of trials assessing subsequent management, (e.g. positive sentinel node adjuvant therapy (POSNOC) which included Australian patients), are eagerly awaited.
Neo-adjuvant chemotherapy (NAC) use is increasing especially in biological subtypes where response can further tailor management. For tumours which are either triple negative or overamplify HER2, a complete pathological response can be seen up to 70% of the time. This gives prognostic information and allows for additional therapy in those without a complete response, leading to improvement in overall survival.
In patients with clinical node negative disease, the timing of SLNB in relation to NAC was initially controversial. It has now been shown to be reliable and safe to be performed following completion of NAC. For those with node-positive disease in the outset, we can see a complete pathological response in the lymph nodes up to 40% of the time, meaning the traditional treatment of ALND may not be required. Nodal response is not always predicted by response in the breast.
Accurately identifying this subgroup of initially node-positive patients who may then avoid ALND is clinically challenging, with 50-60% of patients who have a node that appears to have regressed on imaging will have residual disease in the axilla.
Restaging of the axilla post-NAC may be a useful adjunct. However, several studies have shown the limitations of SLNB in node-positive patients after NAC with unacceptably high false negative rates. Using a dual tracer, (both patent V blue dye and a radioisotope) increased the SLN identification rate and contributed to the lower false negative rate when at least two LN are removed, but still gave a false negative rate above the accepted threshold of 10%.
Targeted axillary dissection (TAD) is a surgical technique that has been developed to further lower the false negative rate and accurately restage the axilla. It is useful in the cohort who were clinically node positive on presentation but have a good clinical response following NAC.
Prior to any treatment beginning, the abnormal nodes are identified on ultrasound imaging. A marker clip is placed in the largest, most abnormal node proven to be FNA positive, under imaging guidance.
This can subsequently be used to localise the lymph node for excision under hookwire, radioactive or magnetic seed guidance. At the time of surgery, the targeted node is excised along with a SNB using dual tracers. The recommendation is to remove at least three nodes. This technique has lowered the false negative rate to 2%, likely aided by the finding that the clipped node is not the sentinel node in about 20% of cases.
Many centres in WA are now adopting this approach in patients with a low nodal burden prior to NAC and a good clinical and radiological response. This is done in a multi-disciplinary setting within department guidelines and protocols. A TAD is considered positive when any amount of residual disease is found in the axilla, and currently standard of care is to perform a completion ALND. Long-term follow-up is awaited for this group, as well as information on the role of nodal radiation in this setting.
Balancing the importance of prognostic information in axillary staging with the significant morbidity associated with axillary treatment means the management of the axilla in breast cancer will remain dynamic. Trials are ongoing and results will influence future care.
Hopefully we can provide accurate staging, low regional recurrence rates and improved overall survival while safely avoiding the life-changing, long term morbidity associated with axillary surgery.
Key messages
- ALND is associated with significant morbidity which greatly influences patients’ quality of life
- SLNB offers accurate staging with fewer complications in the clinically node negative breast cancer patient
- Neo-adjuvant chemotherapy is converting a greater number of node positive patients to node negative, unlikely to benefit from full ALND.
– References available on request
Author competing interests – nil