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Page 7 of 69 1 RATIONALE AND DEVELOPMENT OF SENTINEL LYMPH NODE DISSECTION
Jan H. Wong, MD INTRODUCTION
One of the longest standing and most controversial issues in the management of the
patient with cutaneous melanoma has been the therapeutic value of immediate
lymphadenectomy in the clinically node-negative individual. In 1892, Herbert
Snow [1892] noted that “the danger lies in the diffusion of malignant cells....These
always implicate the nearest lymph glands....Palpable enlargement of these gland
is, unfortunately, but a late symptom of deposits therein....We see the paramount
importance of securing the perfect eradication of these lymph glands which will
necessarily be first infected.” Numerous single institutional reports have suggested
improved survival in patients who undergo immediate lymphadenectomy when
compared with individuals who undergo lymphadenectomy for clinically evident
disease [Balch 1981, Koh 1986, Morton 1991, Roses 1985, Callery 1982]. These
reports, however, have been criticized because of their retrospective nature and the
utilization of historical controls. In contrast, three prospective randomized trials
have failed to confirm the survival advantage noted in these single institutional
retrospective analyses [Balch 1996, Sim 1986, Veronesi 1977] and raised the
possibility that regional nodal metastases might be an indicator of systemic disease
rather than a marker of the orderly progression of disease from the primary tumor.
As a result of the World Health Organization Trial [Veronesi 1977, 1982] the
standard of care in the management of apparently localized cutaneous melanoma
has been considered wide excision of the primary site and observation.
Although a number of alternative explanations to explain the lack of
benefit observed in these prospective randomized trials were proposed, perhaps the
most compelling reason for failing to demonstrate any statistically significant
improvement in survival was the inability to accurately stage patients. It is apparent
that only those individuals with pathologically involved nodes and without
metastatic disease were the only individuals that could potentially benefit from
immediate node dissection. The majority of patients either did not have nodal
metastases or nodal metastases were associated with non-regional micrometastatic
disease. These individuals, therefore, could not even, theoretically, benefit from an
immediate lymphadenectomy. Natural history studies suggests that individuals who
are node positive but without non-regional micrometastatic disease represented only
a small minority of the patients studied in these prospective, randomized trials and
raised the possibility that that these trials might not have had sufficient statistical
power to identify a survival advantage. Additionally, the Intergroup Melanoma
Surgical Program Trial [Balch 1996] was several years away from completion and
analysis.
2 Atlas of Selective Sentinel Lymphadenectomy
Because of the possibility that earlier trials did not have the statistical
power to identify survival advantage, we initiated studies at the University of
California, Los Angeles to determine whether operative approaches could be
developed to identify node metastases in clinically node negative individuals who
could potentially benefit from immediate lymphadenectomy while sparing the
majority of node negative individuals the morbidity of complete node dissection
that would have no potential therapeutic benefit.
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