Traditionally the standard treatment for the axilla in breast cancer is an axillary clearance. This involves the removal of level I and II lymph nodes of the axilla on the affected side of the breast cancer. The aim of this axillary clearance surgery is manifold. Firstly as a staging mechanism to determine the prognosis of the patient, provide local regional control of the cancer, and determine the need for additional adjuvant treatment such as chemotherapy and/or radiotherapy and lastly, some studies have shown that it can confer a certain survival benefit.

However, axillary clearance also results in a certain amount of morbidity to the patient. This may be in the form of immediate problems related to longer surgery, larger scar, or a need to insert a drain post-operatively. In addition, there is risk of injury to structures in the axilla such as the axillary vein and the long thoracic and thoracodorsal nerves. The longer term sequelae of axillary clearance includes seroma formation, numbness over the inner aspect of the arm, decrease in the range of motion and pain of the affected shoulder and also lymphedema of the upper limb. Therefore, the question is, do we need to routinely perform an axillary clearance for all breast cancer patients especially in this day and age where with increasing of awareness and screening, the size of our breast cancers are getting smaller and at the same time the incidence of metastasis or positive lymph nodes is decreasing.

Currently up to two-thirds of our patients with breast cancer do not have any axillary nodal metastasis. Therefore, if the axillary lymph nodes do not contain metastasis perhaps it may be possible to leave these lymph nodes alone and not perform an axillary clearance thereby negating the morbidity associated with this surgical procedure. This would especially apply to our patients with early or screen detected breast cancers.

The concept of sentinel lymph node biopsy has been proposed as an alternative to axillary clearance to determine the axillary status. The word sentinel comes from the French word sentinnele, which means ‘one who stands watch and guards against unlawful entry’. The sentinel lymph node is defined as the first draining regional lymph node from the tumour bearing bed. Sentinel lymph node biopsy has been proposed as early as the 1990s and is widely accepted for other cancers such as penile cancer and melanoma. It was first proposed for breast cancer by Guiliano and Krag in the early 1990s. The premise is that the sentinel lymph node is able to predict the status of the axillary lymph nodes and if the sentinel lymph node is negative, then the axilla does not contain any metastatic disease and therefore there is no need for a full axillary clearance.

The feasibility, technique and method for detecting the sentinel lymph nodes have been studied and the results widely and extensively published. Various validation studies have confirmed the accuracy and low false negative rate of the sentinel lymph node in predicting the axillary nodal status. A prerequisite is a surgeon who has undergone training, overcome an initial learning curve and individually validated, working closely in a multidisciplinary team together with colleagues from the Departments of Nuclear Medicine and Pathology.

Various randomized controlled clinical trials have been performed such as the NSABP B32 study in North America, the ALMANAC trial in the United Kingdom and the Italian sentinel node studies. All these trials looked at the feasibility/accuracy of performing sentinel lymph node biopsy for breast cancer and compared it with standard axillary clearance. Results from these trials have either been published or presented at international conferences and show that sentinel lymph node biopsy is accurate in predicting axillary status, has lower morbidity and on follow up found to be safe oncologically when an axillary clearance is not performed.

The concept of sentinel lymph node biopsy is therefore very attractive as it can predict the status of the axilla, and in those patients where the lymph node is found to be negative, full axillary clearance can be avoided. This leads to lesser morbidity but at the same time allowing closer examination of the few lymph nodes sent to the pathologist.

How is sentinel lymph node biopsy actually performed? It involves an injection of Tc99 sulphur colloid into the skin subdermally just above the location of the tumour. This is usually performed in the morning of the surgery in the Department of Nuclear Medicine. Subsequently, a lymphoscintigram is done to help identify and locate the position of the sentinel lymph node. Two to 4 hours later, the patient is brought to the operating theatre whereby an injection of a blue dye (isosulphan blue) is done intra parenchymally around the tumour. The sentinel lymph node is the node in the axilla which is hot (radioactive) and/or blue in colour. The detection of this node(s) is done with the help of a gamma probe to detect radioactivity and visually looking for a blue node. These lymph nodes are then sent to the pathologist for histology to detect metastasis, and if negative, no axillary clearance is performed.

What have we done so far about sentinel lymph node biopsy here in Singapore? Since late 2003 we have been performing sentinel lymph node biopsy followed by axillary clearance as part of a validation study. Patients eligible would be those with early breast cancer and clinically negative axillas. Our result so far of more than 80 patients have showed that these technique is indeed feasible and can performed here and the false negative rate is 8.7%. The false negative cases were in the initial learning curve and for the last 30 patients there have been no false negative results.

Therefore, as more studies from randomized trials are published it would seem as if sentinel lymph node biopsy is here to stay and will become the new standard of care for treatment of the axilla in early breast cancer patients.

Dr Yong Wei Sean
Consultant
Department of General Surgery
Singapore General Hospital