Background The COCCINELLE study is a nationwide retrospective French cohort set up to evaluate the risk of radiation associated cancer in patients who undergone cardiac catheterization (CC) procedures for diagnosis or treatment of congenital heart disease during childhood [1].Material and methods Children who undergone CC procedures from 01/01/2000 to 31/12/2013 before the age of 16 in one of the 15 pediatric cardiology departments which perform pediatric CC in mainland France were included. The follow-up started at the date of the first recorded CC procedure until the exit date, i.e. the date of death, the date of first cancer diagnosis, the date of the 18th birthday, or the 31/12/2015, whichever occurred first. The cohort was linked to the National Childhood Cancer Registry to identify patients diagnosed with cancer and with the French National Directory for the Identification of Natural Persons to retrieve the patients’ vital status. An external comparison was conducted using standardized incidence ratios (SIR). Breslow and Day’s approximation was used to estimate 95% confidence intervals (CI) for the SIRs [2]. Results A total of 17,104 children were included in the cohort and followed for 110,335 person-years, with 22,227 CC procedures collected. Among the patients, 81.6 % received only one procedure. Fifty-nine cancer cases were observed in the cohort. SIRs were increased for all-cancer (SIR = 3.8, 95% CI 2.9, 4.9), leukemia (SIR = 3.3, 95% CI 2.0, 5.4), lymphoma (SIR = 14.9, 95% CI 9.9, 22.5) and solid cancers excluding central nervous system tumors (SIR = 3.3, 95% CI 2.0, 5.5) compared with the general population. Conclusion Increased risks of cancer were observed. Potential explanations include shared genetic or environmental factors, immunosuppression drugs, and exposure to medical ionizing radiation procedures. The dose-response analysis between ionizing radiation doses received during CCs and cancer occurrence will allow to address this question.Keywords: Ionizing radiation, cardiac catheterization, congenital heart disease, cancerCompeting interestsThe authors declare that they have no competing of interest.References1.Baysson H, Nkoumazok B, Barnaoui S, Réhel J, Girodon B, Milani G, Boudjemline Y, Bonnet D, Laurier D, Bernier M (2015) Follow-up of children exposed to ionising radiation from cardiac catheterisation: the Coccinelle study. Radiation protection dosimetry 165:13–162.Breslow NE, Day NE (1987) Statistical Methods in Cancer Research Volume II: The Design and Analysis of Cohort Studies, IARC Scientific Publication. IARC Scientific Publication No. 82, Lyon, France: International Agency for Research on Cancer.NotesCOCCINELLE: French acronym for COhorte sur le risque de Cancer après Cardiologie INterventionnELLECC: Cardiac CatheterizationSIR: Standardized Incidence Ratios CI: Confidence IntervalsCNS: Central Nervous System