Radioguided sentinel lymph node biopsy in patients with malignant cutaneous melanoma: The nuclear medicine contribution

Abstract

As for other solid tumors, malignant cutaneous melanoma drains in a logical way through the lymphatic system, from the first to subsequent levels. Therefore, the first lymph node encountered (the sentinel node) will most likely be the first to be affected by metastasis, and a negative sentinel node makes it highly unlikely that other nodes in the same lymphatic basin are affected. Sentinel lymph node biopsy distinguishes patients without nodal metastases, who can avoid nodal basin dissection with its associated risk of lymphedema, and those with metastatic involvement who might benefit from additional therapy. This procedure represents a significant advantage as a minimally invasive procedure, considering that only an average 20% of melanoma patients with Breslow thickness between 1.5 and 4 mm harbour metastasis in their sentinel node(s) and are therefore candidates to elective lymph node dissection procedures. The cells that originate cutaneous melanomas are located between dermis and epidermis, a zone that drains to the inner lymphatic network in the reticular dermis, in turn to larger collecting lymphatics in subcutis. Therefore, the optimal modality of interstitial administration of radiocolloids for lymphoscintigraphy and subsequent radioguided sentinel lymph node biopsy is through intradermal/subdermal injection. (99m)Tc-labeled colloids in various size ranges are equally adequate for radioguided sentinel lymph node biopsy in patients with cutaneous melanoma, depending on local experience and availability. For melanomas located in the midline area of the head, neck, and trunk, particular consideration should be given to ambiguous lymphatic drainage, which frequently requires interstitial administration virtually all around the tumor or surgical scar from prior excision of the melanoma. Lymphoscintigraphy is an essential part of radioguided sentinel lymph node biopsy because images are used to direct the surgeon to the sites of the node(s). The sentinel lymph node should have a significantly higher count than that of background (at least 10:1 intraoperatively). After removal of the sentinel node, the surgical bed must be reexamined to ensure that all radioactive sites are identified and removed for analysis. The success rate of radioguidance in localizing the sentinel lymph node in melanoma patients is about 98% in institutions where a high number of procedures are performed, approaching 99% when combined with the vital blue dye technique. The procedure is becoming the standard of care for patients with cutaneous melanoma because of its high prognostic value that has led to include the procedure in the most recent version of the TNM staging system.

Lymphoscintigraphy and clinic

“…Lymphatic mapping using radio colloid reveals ways unexpected of lymphatic drainage, it finds all the stations limph node at a greater risk of metastasis and for each of them, locates the sentinel lymph node; it also allows the identification and biopsy of the lymph nodes in-transit (the lymph nodes under the skin spots between the seat skin of the melanoma and the station lymph node Res Rev Insights, 2017 doi: 10.15761/RRI.1000105 main) [49,50]. With the new generation of large -field of view gamma cameras, SPECT/TC has been incorporated in the SLN procedure.…”

Pesquisa do linfonodo sentinela em pacientes com melanoma: experiência com fitato marcado com Tecnécio-99m e revisão da literatura

“…6 O status do LNS é tão aceito, que foi incluído no estadiamento proposto pela American Joint Committee on Cancer for Malignant Cutaneous Melanoma. 24,25 A detecção de LNS pode ser também indicada para pacientes com lesões mais superficiais (<1mm), 26,27 apesar de ser evidente o fato de que tumores mais profundos apresentam maior probabilidade de disseminação ganglionar. 28,29 O valor prognóstico da biópsia do linfonodo sentinela é comprovado para tumores com espessura acima de 4mm.…”

“…30 Descreve-se a correta identificação intra-operatória do LNS em quase 98% dos casos com colóides radiomarcados, 75 a 80% com corantes e 98 a 99% com a combinação de ambos. 25 Também se descreve acurácia superior a 98% da biópsia do LNS na predição do acometimento de toda a cadeia linfática. 6,12,13 Em recente revisão de 1.135 casos de melanoma, o LNS foi detectado com radioisótopos em 97% dos pacientes, com valor preditivo negativo de 100%.…”

Accuracy and Reproducibility of Lymphoscintigraphy for Sentinel Node Detection in Patients with Cutaneous Melanoma

“…The technique of sentinel lymph node (SLN) biopsy with selective lymph node dissection in melanoma patients has been widely adopted by surgical oncologists as an alternative to elective lymphadenectomy for patients with clinically negative regional lymph nodes who are at high risk for nodal metastases (1,2). The success of this technique has resulted in its use in the treatment of other cutaneous and noncutaneous malignancies with regional lymphatic metastatic potential (3).…”