Détection et valeur pronostique de la maladie minime médullaire et sanguine au diagnostic des rhabdomyosarcomes alvéolaires: étude rétrospective de la socié té française de lutte contre les cancers et des leucémies de l'enfant et de l'adolescent (SFCE)

Purpose Diagnosis of alveolar rhabdomyosarcoma (aRMS) is typically histological and immunohistochemical. Since 1993, we know that this tumor harbors specific fusion transcripts called PAX3-FOXO1 and PAX7-FOXO1. Detection by RT-PCR of one of these transcripts in bone marrow or circulating blood can reveal infra-cytological metastasis. The objective of this study was to determine the frequency of detection of bone marrow (BMM) and/or blood micrometastasis (CMM) in children with aRMS at diagnosis and to assess its prognostic value. Methods This is a French national clinico-biological retrospective study of 34 children and adolescents with rhabdomyosarcoma (RMS), metastatic or localized, of which the initial tumor harbors at least one specific transcript. They all had, at diagnosis, a bone marrow and/or blood sample to search micrometastasis. Results Sixteen percent of patients with localized disease had BMM and 53 % of all aRMS had a CMM. Results indicate that the presence of BMM at diagnosis is associated with a significant decrease in overall survival (10 % vs 60 %; P = 0.0058) and event-free survival (10 % vs 50 %; P = 0.0008), as well as in metastatic stage and localized tumors. We find, moreover, 83 % of relapse or progression in presence of blood micrometastasis. Conclusion With all the limitation of a retrospective analysis - and despite the limited number of patients - this is the first study to examine the pejorative prognostic value of the presence of bone marrow or blood micrometastasis at diagnosis in children with aRMS. It is the first step leading to a large-scale on going prospective study to confirm this assumption. If this is confirm in a larger setting, this would classify patients with bone marrow or blood micrometastasis in a high-risk population, to be treated more intensively or with new therapeutic strategies.