OBJECTIVES : The organized colorectal cancer (CRC) screening of the Basque Country began in 2009 and finished the first round in 2014 for individuals between 50 and 70 years. Our objective was to measure the change on incidence, TNM stages’ distribution and survival of CRC cases before and after the first round.

METHODS : . A retrospective observational design was applied to cases from the Population and Hospital Cancer Registries of Basque Country. Cox regression and relative survival (RS) by TNM stage were calculated in 2003-2006, 2007-2010 and 2011-2014. Adjusted incidence rates were analyzed by joinpoint regression. Since the screening program only had implemented a first round in 2014, it only could change epidemiology of patients under 70 years of age the analysis was disaggregated by age (< 70 and >70 years).

RESULTS : 18,103 cases of CRC were analyzed. From 2003-2006 to 2011-2014 early cases increased significantly. The death hazard ratios for the 2003-2006 four-year period compared to 2011-2014 were 1.35 for stage I, 1.29 for stage II and 1.30 for stage III; all of them being statistically significant. From the first to the third four-year period, the RS increased significantly from 0.67 to 0.82 in the cases younger than 70 while older cases did not change significantly. Incidence analysis showed a significant drop from 2013 in cases younger than 70 years.

CONCLUSIONS : There was a relevant change in the epidemiology of CRC in the Basque Country for each TNM stage that can be associated with the first round of the screening program since survival increased, incidence decreased and cases were diagnosed in earlier stages only in cases younger than 70 years. In those over 70 years of age, who were not target population, epidemiology did not change