Contribution of Oncogenetics in Breast Cancer in Reunion Epidemiology of Breast Cancer in Reunion: Study of the Reunion Mutation on BRCA2

In mainland France, breast cancer is the most common cancer in women, with an estimated incidence of over 58,000 new cases. Even if breast cancer is a cancer with a good prognosis, it is responsible for more than 12,000 deaths per year (first cause of death by cancer in women in France). Breast cancer is a multifactorial disease, which results from the interaction between environmental, lifestyle, hormonal and genetic risk factors. In Reunion, more than 400 cases of breast cancer are diagnosed annually. As in mainland France, it is by far the most common cancer in Reunionese women, and its incidence continues to increase significantly since the age-standardized incidence rate increased by 28% between 2007 and 2017 to establish at 64.2/100,000 AP. Two studies carried out in patients carrying mutations in the breast-ovary predisposition genes in Reunion, showed that more than 50% of patients carrying BRCA mutation have a mutation specific to the Reunion population on the BRCA2 gene. These two studies, which confirm the genetic specificities of Reunion already described in other pathologies (Mucoviscidosis or Friedreich's Ataxia), suggest that this mutation could have a significant frequency in patients with breast cancer. Thus, evaluating the prevalence of this mutation in patients with breast cancer in Réunion would make it possible to adapt the indications for access to the oncogenetics consultation and the associated preventive measures