Received: 22 February 2017
Accepted: 5 February 2018
First Online: 13 February 2018
Ethics approval and consent to participate
: This study was approved by the local ethics committee of Gustave Roussy (n°26/007). The parents/guardians gave their written informed consent for the retrospective analysis of clinical data according to the institutional review board of the Gustave Roussy Campus.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.