The https://www.vallhebron.com/en/specialities/paediatric-oncology-and-haematology Pediatric Oncology Service of the Vall d'Hebron University Hospital, headed by Dr. Soledad Gallego, launched in 2016 the Comik program (Cancer Omics for Kids) of personalized medicine in solid childhood tumors. This program makes it possible to perform a comprehensive genetic analysis of tumors in cases in which patients do not respond to current treatments or who are in a situation of relapse. In this way, a specific molecular signature of each tumor can be obtained. A signature that is unique to the tumor of each patient, and that may allow the use of targeted therapies based on the molecular abnormalities detected.Cancer in pediatrics is different from adult cancer, both in its origin and its types and in its evolution. Pediatric tumors are the result of specific genetic and molecular alterations of each patient that occur early during development or in the early stages of life, so, unlike adult tumors, they are not associated with the lifestyle or with environmental risk factors. As explained by Dr. Raquel Hladun, from the Pediatric Oncology Service of Vall d'Hebron, "analyzing tumors at the molecular level allows us to identify mutations or other molecular anomalies of the tumor of each patient, that is, obtain their molecular signature." Despite advances in survival, up to 25% of pediatric tumors currently have no cure. The Comik program aims to identify effective therapies for the subgroup of patients with poor prognosis.Vall d'Hebron has taken another step in the field of personalized medicine for childhood cancer. As Dr. Gabriela Guillén from the Pediatric Oncological Surgery Unit of Vall d'Hebron points out, "we took a sample of the tumor to be able to perform the molecular analysis, and a small part of the extracted tumor tissue was implanted in mice". In this way, the tumors evolve in the mice and the experts can test different treatments. Currently, this technique is already performed in other centers on solid infant tumors, although, in most cases, the implantation of the tumor takes place in the subcutaneous tissue of the animal. In contrast, in the Comik program, the patient's tumor tissue is implanted in the same organ or area as the original tumor. Therefore, a lung tumor is implanted in the mouse lung, a brain tumor is implanted in the mouse brain, or a liver tumor is implanted in the mouse liver. Vall d'Hebron is a pioneer in the use of this technique in a child cancer program that allows the creation of "mirror tumors" of patients. "These mirror tumors grow and evolve in the mouse more closely to tumors that are implanted under the skin, since the behavior of tumors depends on the environment in which they are. Therefore, it is not the same as the tumor evolves under the skin to do so in the organ of origin. The evolution of these mirror tumors is more similar to what occurs in the patient", adds Dr. Gabriela Guillén,"In this way, personalized treatments for the specific tumor of each patient can be tested in mice in a much more valid and reliable way ". Once the mirror tumor is implanted, the experts test different treatments in the mice according to the targets that have been identified in the previous molecular analysis. If a treatment is effective and does not offer serious side effects, it is proposed to be used in patients. "It is a way to try new therapies in relapsed or high risk tumors, avoiding the patient's exposure to ineffective drugs", emphasizes Dr. Raquel Hladun.Thanks to the Comik program, which was implemented in Vall d'Hebron in 2016, "we have identified molecular targets that have allowed us to use personalized therapies in 35% of the 40 patients included in the program," adds Dr. Raquel Hladun. Patients who have benefited from Comik include children and adolescents with bone sarcomas (osteosarcoma, Ewing's sarcoma and chondrosarcoma), rhabdomyosarcomas, non-rhabdomyosarcoma soft tissue sarcomas (including patients with malignant rhabdoid tumors, desmoplastic small cell tumor, alveolar sarcoma of soft tissues and undifferentiated sarcoma), neuroblastomas, hepatic tumors (hepatoblastoma and hepatocarcinoma), thyroid carcinoma, high grade gliomas and diffuse trunk tumors. As explained by this expert, "thanks to the analyzes carried out, we have identified molecular targets that have allowed the use of more than eight different targeted therapies, some of them already approved drugs, other therapies in clinical trials, and others of programs of access to drugs in research outside clinical trial. As our knowledge of childhood cancer progresses, thanks to the data generated by our project and other similar projects that are being carried out internationally, we are able to define new molecular targets and drive the development of new therapies. In this way, more and more patients will benefit from the Comik program."In parallel, Dr. Gabriela Guillén adds "the generation of mirror tumors is allowing us to create a bank of mirror tumors to test new therapies that appear in the future. Maybe now there is no therapy for a particular tumor, but it may exist in a few months." The program, so far, has managed to establish 24 models of orthotopic PDX (the scientific name for these "mirror tumors" in mice), which represent up to eleven different types of pediatric tumors, including neuroblastomas, soft tissue and bone sarcomas, nephroblastomas or liver tumors. Large European study of personalized medicineThe Comik program is carried out thanks to the team work of pediatric oncologists, pediatric surgeons, pediatric anatomo-pathologists, pediatric radiologists and basic and translational researchers. This program, promoted and directed by the Pediatric Oncology Service of Vall d'Hebron, is one of the priority research lines of http://en.vhir.org/portal1/grup-equip.asp?s=recerca&contentid=186749 the Translational Research Group in Child and Adolescent Cancer, led by Dr. Soledad Gallego, del Vall d'Hebron Research Institute (VHIR), and it is carried out in collaboration with Dr. Alberto Villanueva, of the Biomedical Research Institute of Bellvitge (Idibell). Now, in addition, the program will be integrated into a large European study of personalized medicine "Stratification of molecular profiles in the treatment of pediatric and juvenile cancer" (Mappyacts)."The treatment of cancer goes through personalized medicine, -says Dr. Raquel Hladun- Therefore, in Vall d'Hebron we work to find ways to apply the advantages of personalized medicine in clinical practice." Challenges in pediatric cancerPediatric cancer is considered a rare disease since it affects 1 in 7,000 children under 15 years of age (230 new cases per year in Catalonia and 1,400 in Spain). Although it is curable in 75% of cases, it is necessary to continue research to identify the molecular alterations that define it, and thus to rescue the subgroup of patients considered to have a poor prognosis. "In this sense, much more progress has been made in adult cancer than in childhood cancer. In large part, because pediatric cancer is a minority disease. It is necessary to devote more resources to research," says Dr. Raquel Hladun.