Cancer has recently become the leading cause of death worldwide according to the World Health Organization. As a consequence, health authorities acknowledge the need to implement prevention and screening programs to decrease its incidence. The efficiency of these programs can be increased by targeting higher risk subsets of the population. Efficient tools capable of monitoring the population risk are therefore needed. Constraints to building cancer risk scores and impacts on the tools platform are presented. Major constraints beyond performance of a risk score concern the role of domain experts and their acceptability by end users. Readability is therefore an important criterion. It is shown that a simple k-nearest-neighbor algorithm can achieve good performance with the help of the domain expert. To illustrate this, a risk score made of only four attributes is presented for the French population.