Originally published as JCO Early Release 10.1200/JCO.2008.19.5420 on November 17 2008

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The Rotterdam Criteria for Sentinel Node Tumor Load: The Simplest Prognostic Factor?

Alexander C.J. van Akkooi, Johannes H.W. de Wilt, Cornelis Verhoef, Alexander M.M. Eggermont

Department of Surgical Oncology, Erasmus University Medical Center-Daniel den Hoed Cancer Center, Rotterdam, the Netherlands

To the Editor:

With great interest we have taken notice of the article in Journal of Clinical Oncology by Gershenwald et al, ¹ entitled "Microscopic Tumor Burden in Sentinel Lymph Nodes Predicts Synchronous Nonsentinel Lymph Node Involvement in Patients With Melanoma." The paper by Gershenwald et al presents us with additional and convincing results to an already growing amount of evidence that patients with minimal sentinel node (SN) tumor burden have a low risk of non-SN metastases in the completion lymph node dissection (CLND) specimen.

Among the different ways to measure SN tumor burden, they have used the maximum diameter of the largest lesion and the square area of the SN involved by a metastasis. The measurement of the maximum diameter of the largest lesion is a method also used by us and others, however with different cutoff values.^2-4 This situation begs for a comparison of the results in the Gershenwald paper with those from other centers utilizing cutoff values of 0.1 mm and 0.2 mm.

The second question regards the square area of the SN involved by tumor: How did you measure this surface area? This is not so simple as SN metastases are often not confined to one single slide or even to one single area on a slide. Moreover, metastases are often not easy to measure as square figures, but can have many curves while they spread along the capsule of the lymph node. This obviously makes such measurements unreliable. These simple limitations reduce the value of SN tumor square area as an easy and accurate clinical characteristic to measure SN tumor burden. In contrast, it is our experience that the measurement of the maximum diameter of the largest lesion is the easiest and best reproducible characteristic to measure SN tumor burden.^2,4

Although not entirely comparable, the results by Gershenwald et al¹ do add to the evidence that the Rotterdam criteria^2,4 for the measurement of SN tumor burden are the best predictor for non-SN involvement. If we consider that the square root of 0.1 mm² is 0.32 mm, the average 0.1 mm² lesion will be 0.32 x 0.32 mm. In the present study 27.8% of all SN positive patients have such a SN tumor burden. This is similar to the 20% of patients with sub-micrometastases ( 0.1 mm), as reported in Rotterdam and Berlin.^2,4 Moreover the 3.7% non-SN positivity rate for such minimal SN tumor burden is virtually identical to the 3% reported by us in a similarly sized multicenter experience.^2,4

Table 1 summarizes the results of some recent pivotal studies with regard to SN tumor burden in melanoma patients. We urge the use of uniform, simple and practical criteria for SN tumor burden, to facilitate scientific efforts to identify a patient group, which can safely be spared a completion lymph node dissection.

The author(s) indicated no potential conflicts of interest.

NOTES

published online ahead of print at www.jco.org on November 17, 2008.

REFERENCES

1. Gershenwald JE, Andtbacka RH, Prieto VG, et al: Microscopic tumor burden in sentinel lymph nodes predicts synchronous nonsentinel lymph node involvement in patients with melanoma. J Clin Oncol 26:4296-4303, 2008[Abstract/Free Full Text]

2. van Akkooi AC, de Wilt JH, Verhoef C, et al: Clinical relevance of melanoma micrometastases (< 0.1 mm) in sentinel nodes: Are these nodes to be considered negative? Ann Oncol 17:1578-1585, 2006[Abstract/Free Full Text]

3. Govindarajan A, Ghazarian DM, McCready DR, et al: Histological features of melanoma sentinel lymph node metastases associated with status of the completion lymphadenectomy and rate of subsequent relapse. Ann Surg Oncol 14:906-912, 2007[CrossRef][Medline]

4. van Akkooi ACJ, Nowecki ZI, Voit C, et al: Prognosis depends on micro-anatomic patterns of melanoma micrometastases within the sentinel node (SN): A multicenter study in 388 SN positive patients. Eur J Cancer Supp 5:397, 2007

5. Scheri RP, Essner R, Turner RR, et al: Isolated tumor cells in the sentinel node affect long-term prognosis of patients with melanoma. Ann Surg Oncol 14:2861-2866, 2007[CrossRef][Medline]

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