NBoCC position statements
Sentinel node biopsy in breast cancer
by the Breast Section of the Royal Australasian College of Surgeons
9 October 2005
In 2002 the Executive Committee of the Breast Section of the RACS developed a position statement on sentinel node biopsy (SNB). At that time SNB was still being evaluated in clinical trials around the world, including our own SNAC trial. The 2002 position statement indicated that SNB should only be promoted in the context of a randomised clinical trial. If it was to be done outside of this scenario then the woman should be informed of the limitations of the technique, the lack of long term data, as well as the surgeon’s own results with the technique. We now feel that the position statement needs to be updated, as new data has become available, and the SNAC trial has completed accrual. This updated statement should be reflective of the current safe use of the technique and should be noted by breast surgeons who offer the technique to women with early breast cancer, depending on their own circumstances and experience.
SNB in early breast cancer has been investigated and researched for greater than 10 years now. Four major randomised controlled trials (3 multicentre) have been conducted, all of which have completed recruitment (ALMANAC - United Kingdom, Milan, NSABP-B32 - North America, SNAC Trial - Australia and New Zealand). The Milan trial published its early results in 2003 whilst the ALMANAC and NSABP-B32 trialists have presented initial results at international meetings in 2004. The results of these trials and those from a large number of single and multi-institution validation series show remarkably similar data.
SNB appears to be an effective method for the staging assessment of the clinically negative axilla, comparable to level 2 axillary dissection. It seems to have significantly less morbidity than level 2 axillary dissection, as demonstrated by presentations from the ALMANAC trial at the San Antonio Breast Cancer Symposium in 2004.
SNB is very much operator dependent, with the literature reporting a wide range of sentinel node detection rates and wide range of false negative rates. As such, individual surgeons and institution teams beginning to introduce SNB should undergo an educational program. A period of self / institution audit is then mandatory. Individuals should audit their success rate at identifying the sentinel node, and their false negative rate, by performing SNB followed by immediate level 2 axillary dissection. These results should be comparable to accepted standards (ie similar to standards set by the SNAC trial – sentinel node identification in >90% in 20 consecutive cases). The number of cases required to confirm competency should be 20 – 40, depending on progress. Once validated, ongoing data should be kept to monitor performance and compared to accepted rates of positive node detection and local recurrence.
The reported false negative rates range from 5 -15%. This data will only be known during the validation phase where immediate axillary dissection is performed. It should be calculated in reference to the number of node positive cases, not the total group. The false negative rate appears to remains constant for an individual surgeon across all cases. The significance of the individual surgeon’s false negative rate relates to the percentage chance of an individual woman having a positive lymph node in the axilla i.e. related to size, grade, and lymphovascular invasion. For small, screen-detected low grade cancers the prevalence of axillary lymph node involvement is low (< 5 % in some cases). As such, the chance of leaving disease within the axilla after SNB is minimal. With larger tumours the incidence of positive nodes is up to 70 %. In this scenario a surgeon with a 15% false negative rate has an overall chance of missing node positive disease of 10%. Women having SNB should understand the significance of the surgeon’s false negative rate, in terms of risk of regional relapse, potential for understaging and possible impact on adjuvant therapy decisions.
The role of SNB in larger T2/T3 tumours and multicentric tumours is experimental. There is some encouraging level 3 evidence that SNB is reliable in these situations, but false negative rates seem to be higher. The published series tend to be smaller than the early reports of SNB in early breast cancer. Rather than offering SNB alone in these groups it would be preferable to enroll patients in a randomised controlled trial, if available. If SNB is performed outside of a clinical trial, the operator should subject these cases to the same rigorous audit and evaluation as recommended above. The use of lymph node biopsy in pure DCIS is not supported by the NBCC Early Breast Cancer Guidelines. There is currently no high level evidence to support SNB in pure DCIS outside a clinical trial.
The assessment of extra-axillary nodal basins is controversial and remains the subject of investigation. Extra-axillary nodal status may alter individual patient management decisions. If it can be performed with minimal morbidity it would be a reasonable option to consider. The SNAC protocol recommended that an attempt be made to biopsy each sentinel node identified.
There are several international studies (e.g. IBCSG Trial 23-01) designed to assess the need for completion axillary dissection with positive sentinel node biopsy in cases of minimal involvement of the sentinel node. Until the results of such trials are available, the standard of care for a positive SNB should be level 2/3 axillary dissection. The Breast Section encourages surgeons to contribute patients to IBCSG Trial 23-01, which is being administered by the ANZ Breast Cancer Trials Group.
The significance of sentinel nodes positive on immunohistochemistry (IHC) only has not been conclusively evaluated. The prognostic implication of micrometastases (>0.2mm and <2mm) or isolated tumour cells (<0.2mm) in sentinel nodes, especially when detected by IHC alone, is unclear and remains the subject of investigation. Where possible it is recommended that pathological evaluation of the sentinel node follow the SNAC trial protocol, with IHC for each sentinel node, in addition to multiple levels on H&E. Ethically approved randomised controlled trials that further investigate the role of SNB in early breast cancer should be supported by the members of the Breast Section.
Remuneration for SNB performed in Australia is currently the subject of an application by members of the Executive Committee of the Breast Section to the Medical Services Advisory Committee of HIC. Until reviewed by the regulatory bodies within Australia, Medicare item number 30332 is the only one approved for SNB.
In conclusion sentinel node biopsy can be offered to clinically node negative women with early breast cancer as an alternative to level 2 axillary node clearance, with the aforementioned points kept in mind. The risks and potential benefits of both procedures should be discussed with patients to allow them to make an informed decision about the surgical management of the axilla. The position statement of the Breast Section of the College is summarised in point form below.
5 POINT SUMMARY
- Many descriptive studies and several randomised controlled trials have shown sentinel node biopsy to be a viable alternative to level 2 dissection for staging the axilla in smaller, clinically node negative breast cancer, with significantly less morbidity.
- The technique is accurate, but there are a small number of false negative cases. The clinical significance of this is currently unknown, and results of randomised controlled trials are awaited.
- Surgeons commencing sentinel node biopsy should audit their results against level 2 dissection, using the SNAC trial protocol as a guide, prior to offering sentinel node biopsy as standard practice.
- The role of sentinel node biopsy in DCIS, multifocal and larger tumours requires further investigation.
- The Breast Section encourages surgeons to contribute patients into randomised controlled trials further investigating the role of sentinel node biopsy in breast cancer.