Sentinel node biopsy: a revolution in the surgical management of breast cancer?

The application of sentinel node biopsy to the surgical management of carcinoma of the breast is still in its earliest stages of development but the first indications are that this technique will prove to have considerable relevance. Initial data show that identification of a sentinel node or nodes is possible in most women and that the presence or absence of metastasis in this node is a very accurate predictor of overall axillary node status. Some studies have compared sentinel nodes that have been examined using serial sectioning and immunohistochemistry with the rest of the axilla viewed with H and E staining and only one level per node. This not only has the effect of increasing the number of node-positive cases but it also maximizes the reported sensitivity of sentinel node biopsy in predicting the presence of regional nodal disease. The temptation to examine the sentinel nodes with the greatest possible degree of accuracy highlights one of the major problems related to sentinel node biopsy in carcinoma of the breast. Information regarding micrometastatic spread is likely to become increasingly available even though the relevance of these data to clinical management is at the present time unclear. In the worst-case scenario it may turn out that this additional information is clinically unhelpful, but as more knowledge concerning the behaviour of early metastasis in breast cancer accumulates it is probable that clinical management will in the end benefit. Similarly, techniques that employ routine lymphoscintigraphy will provide the surgeon with novel individualized information on the direction of lymph flow and the relevant nodal basins. The management of women with lymph drainage predominantly to internal mammary or supraclavicular fossa nodes is a dilemma which may force a change in the way that the axilla is routinely treated. If it is accepted that the prognosis of women who have no treatment at all to the axilla is adversely affected, the results of standard axillary treatment in patients with unusual patterns of lymph drainage could also turn out to be inferior. Some of the present techniques of sentinel node localization deliberately target the axilla, by injecting tracer on this side of the tumour only, and it may be that this bias is unjustified. As with all new developments in surgery, results are dependent not only on the different methods by which a similar goal is achieved but also on the personal experience of the operator with their own variation of the technique. Optimal methods often take more time than might be expected to become established. Questions concerning the advantages of dye or tracer localization, doses of isotope and the role of pre-operative lymphoscintigraphy are likely to be topics of debate for some time and it may well be that, in the final analysis, there is more than one effective way to perform sentinel node biopsy. There are also a myriad of potential new tumour cell specific radiotracers that are presently under development. These will all require critical appraisal before the increased complexity and cost can be shown to be justified by even greater accuracy than is at present achieved with simple tracers. It is apparent, particularly from the experience of Veronesi et al., that the problems of using frozen section analysis of the sentinel node will make one stage surgery including sentinel node biopsy too inaccurate for safe clinical use at present. A rapid immunohistochemical stain for cytokeratin has been described and may be one way of circumventing this practical problem. However, sentinel node biopsy is a minor procedure in itself and it would be possible to incorporate a sentinel node biopsy under local aneasthetic into the routine pre-operative work-up. Alternatively, the technique could be reserved for groups of women at low risk of having axillary metastases so that the incidence of false-negative results requiring second operations will be acceptably low. Other modalities of axillary node staging have been covered in this review. Although these offer a degree of accuracy, it is unlikely that non-invasive procedures will be able to detect micrometastatic disease with the sensitivity promised by sentinel node biopsy.