Towards quality assurance of the sentinel node procedure in malignant melanoma patients: a single institution evaluation and a European survey.

The status of the regional lymph node (LN) is a critical component in staging patients with malignant melanoma. Biopsy of the first tumour-draining LN (sentinel node, SN) may replace routine elective LN dissection. However, until now, the applied methods have differed widely. Therefore, the aim of this study was to formulate recommendations for the pre-operative identification and intra-operative retrieval of the SN. We present the results of an independent survey of the clinical practice of the SN procedure via a postal questionnaire among 136 nuclear physicians in different institutes throughout 16 European countries. Moreover, the results of the SN procedure in our institution in an open prospective intervention trial in 80 patients with malignant melanoma without palpable LNs are also presented. In our protocol, on average, 6 h prior to surgery, 80 MBq technetium-99m nanocolloid was injected intracutaneously around the circumference of the diagnostic excision scar of the primary melanoma. No additional blue dye procedure was used to judge the accuracy of the radioguided SN procedure on its own. For successful identification of the radiolabelled SN, dynamic and static images were performed and the skin projection of the detected SN was marked with a cobalt-57 source. For intra-operative mapping a hand-held gamma probe was used. Forty of the 83 respondents of the European-wide questionnaire (48%) performed the SN procedure. Although many different regimens are used, the following recommendations could be deduced for the SN procedure in patients with malignant melanoma and non-palpable LNs: (1) local, intradermal injection of 40 MBq 99mTc-nanocolloid around the diagnostic excision scar of the primary melanoma; (2) two-phase LS: dynamic imaging (20 frames of 60 s, 128x128 matrix, LEAP collimator) followed by static images 1-2 h later (180 s per record); (3) intra-operative retrieval of the SN with a gamma probe; (4) histopathological examination of the SN on serial sections. In our trial, surgical retrieval of the SN was successful in 95% of the cases. Dynamic lymphoscintigraphy (LS) contributed to the SN procedure by showing anatomically unpredictable lymph flow to extra-regional SNs (10% of the patients in this study) and multiple SNs. Of the 77 retrieved SNs, 13 contained metastatic disease (17%). Consequently, these patients underwent a formal LN dissection of the affected basin. In conclusion, the SN concept is a rational approach to select patients who could, theoretically, benefit from early LN dissection of the affected basin. Standardisation of the SN procedure will improve the results of this approach, and could be useful for quality control and for making comparisons with other countries in coming years.