Moreover, a prospective study conducted as part of a clinical trial would make it possible to determine whether the increase in CDA activity and mRNA levels in the blood of BC patients after treatment is of prognostic value for predicting the course of the disease or the response to treatment, and for determining whether the decrease in CDA activity in response to hormone therapy can be considered an additional benefit of this treatment of potential prognostic value for predicting the risk of relapse. The gene discussed is CDA; the disease is breast cancer.