Molecular diagnosis: a valuable tool against childhood cancer

1977-2017. The pediatric department at Institut Curie is 40 years old, and is a specialty that remains one of the central priorities of Institut Curie’s institutional project, MC21. It takes in around 300 young patients each year, in its unit dedicated to the very youngest children or the one for adolescents and young adults. Its research center has long been a contributor to major advances in the knowledge and treatment of pediatric cancers. This is true of the work of Olivier Delattre, who discovered the genetic anomalies that lead to Ewing’s sarcoma, tumors of the bone that affect children and adolescents, and in several other cancers. These types of discoveries help in the treatment of children with cancer, thanks to the progress in molecular diagnosis, which can distinguish between tumors of similar appearance, which would previously have been treated according to the same protocol. “Tumors are by nature difficult to distinguish. This is all the more true in children: cancerous cells which multiply very fast look very similar to their normal cells which are growing,” explains Gaëlle Pierron, assistant head of Institut Curie’s somatic genetics unit, working with Olivier Delattre. Molecular diagnostics is therefore a precise and indisputable signature of cancer.

“For all ages groups combined, there are 100 different types of sarcoma, which sometimes call for very different treatments. It is therefore very important to obtain the correct diagnosis in order to offer the appropriate treatment,” explains Olivier Delattre. “At the forefront of sequencing technologies and genome analysis, Institut Curie is able to diagnose all pediatric cancers accurately, including the rarest and most complex,” adds Gaëlle Pierron. “All children treated at Institut Curie receive this molecular diagnosis, but as a benchmark center, 90% of our business comes from outside. We handle around 1,400 cases each year, which may require several analyses and we strive to perform these as quickly as possible in order not to delay treatment.”

New hope

In order to limit invasive procedures and to deal with the issue of very small sample sizes, Institut Curie is developing innovative approaches, such as the study of circulating DNA. As soon as a tumor appears, fragments of its DNA can be found in the blood flow. The cancer can then be identified precisely through a simple blood sample. Irène Jimenez, from the department of translational research in pediatric oncology, has just launched a national prospective study to establish the feasibility and relevance of molecular diagnosis in children with kidney tumors using “blood biopsies.”

To ensure that as many children as possible can benefit from these new tools, Institut Curie also wants to spread its expertise: “Molecular analysis is now a vital approach to be used in conjunction with the other analyses. It is important that physicians know that they can send us samples at a very early stage,” Gaëlle Pierron tells us.