The Marie Curie School in Nogent-sur-Marne was built in 1969 on the site of a former radium extraction plant. People who attended the school were exposed to radiation due to radioactive waste present in the subsoil. A retrospective cohort study was conducted among the 3,403 individuals who regularly attended the school until its closure in 1998. Contact information for these individuals was obtained using the national cross-system registry of health insurance beneficiaries. The study focused on analyzing the incidence of cancers and leukemias, as well as associated mortality. Among former students, a significant excess risk of leukemia was observed (Standardized Incidence Ratio = 4.6, 95% CI [1.66–9.89]). Due to the high proportion of lost-to-follow-up cases (42%) and the bias generated by the registry’s preferential recruitment of sick individuals, the observed results cannot be considered conclusive. The difficulties encountered justify placing greater emphasis on the feasibility study in the future. (R.A.)