This was a prospectively designed cohort study carried out in the Hospital de Carabineros de Chile (HOSCAR) and the Hospital de la Dirección de Previsión de Carabineros de Chile (DIPRECA), the immunocytochemistry was performed at the Instituto de Bio-Oncology, Santiago, Chile during the period January 2008 and December 2010. The study protocol and written consent form was approved by the ethical committees of all three centers and all patients signed a written consent form. The study was directed with complete conformity to the principals of the Declaration of Helsinki (together with the modifications of Tokyo, Venice and Hong Kong)
