Screening programs using the guaiac-based fecal occult blood test (gFOBT) for early detection of colorectal cancer are known to result in a reduction in disease-specific mortality. Testing methods based on immunochemical detection reactions (FIT) are considered more sensitive, which is why an Italian study has now tested what effect such screening programs have on mortality.
First, Zorzi et al. disease-specific mortality in the Veneto region of Italy, where 50-69 year-olds have been asked to participate in a screening program with immunochemical testing procedures since 2002. If the test result is positive, each patient is referred to colonoscopy. Second, the researchers evaluated colorectal cancer incidence data between 1995 and 2007, as well as rates of major surgical resections (2001-2012).
In addition, they divided the region into two areas and compared the respective mortality rates: In one, screening had been introduced early, between 2002 and 2004; in the other, screening efforts did not start until 2008 and 2009.
The sooner the better
Main conclusion of the study: compared with the period before the program was introduced, mortality rates between 2006 and 2011 were significantly 22% lower in areas where screening had been introduced earlier than in other areas. Prior to the start of the program, the areas studied had had comparable mortality. This is not surprising – the earlier early detection is implemented in a region, the faster effects on mortality are found. More relevant is the fact that the mortality benefit was seen as early as four years after the introduction of screening, and thus earlier than with guaiac-based methods. After ten years, the mortality reduction was 22%, which is also more pronounced than the known values of gFOBT (population-based studies of gFOBT screening programs in different countries achieved values of 10-16%). According to the authors, this could also be due to better compliance with the FIT or the fact that more of those invited to the screening actually took part in it.
Between 2006 and 2011, mortality in areas with early adoption of the test decreased by 24% (22% in men, 32% in women) compared with 1995-2000. Women thus benefited more from preventive care than men. According to the authors, it should not be forgotten that throughout the study period, treatment options and efficacy also evolved, which could have a partial impact on mortality.
Incidence and surgical resections
Incidence and surgical resection rates peaked at the beginning of the screening effort. While incidence returned to baseline levels between 2006 and 2007 in early-screened areas, the rate of surgical resection after 2007 actually fell below initial levels (ten years after initiation, it was 30% lower). According to the authors, this is also related to the fact that endoscopic resection was possible in almost 20% of cases detected by screening. The initial increase in incidence is self-explanatory: if screening is performed, more carcinomas are found than without screening. The fact that the rate subsequently declined again – and will probably even decline in the long term – is due to the fact that not only full-blown carcinomas but also precancerous lesions (i.e. advanced adenomas) are being detected and removed more frequently. Thus, fewer carcinomas occur overall in the long term. In the present study, the effect on incidence was already apparent in the third year after introduction and thus also earlier than with the gFOBT procedure, where it is usually found only after a long delay.
Source: Zorzi M, et al: Impact on colorectal cancer mortality of screening programs based on the faecal immunochemical test. Gut 2015; 64: 784-790.
InFo ONCOLOGY & HEMATOLOGY 2015; 3(11-12): 3.
