Consensus formalisé d’experts pour la prise en charge du carcinome à cellules de Merkel

Abstract

Merkel cell carcinoma (MCC) is a rare form of tumour that develops from neuroendocrine skin cells. There is no consensus concerning diagnosis and therapy for this disease. To establish recommendations, the Skin Oncology Group of the French Dermatology Society drew on existing recommendations in the US and Germany. Concordance between the two sets of recommendations was validated by the group, who, in view of the large number of discrepancies, decided to use the formalised expert consensus method. Twelve practitioners known for their experience in the management of Merkel cell carcinoma completed a standardised questionnaire. This group consisted of seven dermatologists, three radiotherapists and two plastic surgeons. They answered a total of 82 questions concerning the diagnosis, treatment and follow-up of MCC. A strong consensus was declared where all answers were in the same third of the table; a weak or relative consensus was declared where answers overlapped for adjacent scores, and an absence of consensus was declared in the event of dispersal of values. On completion of this process, the method revealed strong concordance on the following points: value of CK7 and CK20 immunolabelling; lack of value of chest radiography in the initial work-up, but value of lymph node ultrasound; inadequacy of an excision margin of 1cm but lack of any need for a margin greater than 3cm; absence of any value of chemotherapy for inoperable tumours; value of seeking sentinel nodes in tumours measuring less than 2cm outside the head and neck and more than 2cm for head and neck tumours; value of additional radiotherapy at the initial tumour site. Relative agreement was reached concerning the value of thoracic-abdominal-pelvic computed tomography (CT) scans in all cases, together with a head CT scan for cervical-facial tumour sites. The creation of a formalised expert consensus helps complete the existing recommendations, particularly on those points where no consensus exists between the American and German recommendations and where no strong evidence is to be found in the literature.