Screening for colorectal cancer leads to a more favourable stage at diagnosis

In 2003 the countries of the EU agreed to start screening for colorectal cancer (CRC). Currently, several EU countries have implemented a screening programme. As the result of the detection of prevalent cancers with a biannual faecal immunochemical test (FIT) accompanied by an aging population and an increased risk of developing CRC, the incidence of CRC will rise with 35% by 2020 in the Netherlands.1 ,2 Implementation of a screening programme will lead to a more favourable prognosis at diagnosis through the detection of CRC at an early, asymptomatic stage. Of all cancers detected with a single guaiac faecal occult blood test (GFOBT) or FIT, 64–71% will be at stage I or II, compared with 45–60% in matched non-invited symptomatic populations, with FIT showing superiority over GFOBT.3 ,4 The introduction of CRC screening will detect on average 1600 additional stage I and II CRCs per year in the first few years after its introduction in the Netherlands.4 ,5 Interval cancers will still be diagnosed in between screening rounds because not all cancers will be detected when asymptomatic.6 The stage distribution of these interval cancers will mimic those diagnosed in a symptomatic non-screened population.3 ,7 When taking these interval cancers into account, computational models reveal an increase in the proportion of CRCs diagnosed at stages I and II from 53% to 80% without and with annual FIT screening, respectively. Accordingly, a decrease in the proportion of CRCs diagnosed at stages III or IV from 47% to 20% with screening has been predicted. Identical shifts in stage distribution have been observed for all investigated screening strategies.8 Although there might be a selection bias towards an unfavourable stage distribution in the anticipated 40% of the invited population not attending CRC screening, preliminary studies …