Organized colorectal cancer screening program with FOBT: participation and diagnostic yield deteriorate with time.




Bernard DENIS, Isabelle GENDRE, Philippe PERRIN.
Association pour le dépistage du cancer colorectal en Alsace (ADECA Alsace)

Guaiac based fecal occult blood test (gFOBT) is the only screening tool with high-quality evidence obtained from randomised controlled trials (RCTs) demonstrating its efficacy to reduce colorectal cancer (CRC) mortality. However, it has some drawbacks, one is the requirement for frequent testing, which may limit compliance and thereby effectiveness.


Aim        

to assess the short term outcomes of the 2nd round of a biennial gFOBT CRC screening program.


Methods        

Comparison of the outcomes of the 1st and 2nd rounds (R1 and R2) of the organized CRC screening program with Hemoccult II implemented in the Haut-Rhin, a French administrative area, since 2003 (Denis B et al Gut 2007;56:1579-84).
Results: Main outcomes are presented in the table. The crude participation rate decreased from 49.0% to 45.0%. 57.0% of excluded people had a recent < 5 years colonoscopy and 37.5% were at increased CRC risk. 28.4% of people who had participated in R1 did not participate in R2 and conversely, 25.4% of people who participated in R2 had not participated in R1. 83.9% of the completed gFOBTs were provided by general practitioners (GPs) and 12.1% by direct mailing in R2 and respectively 78.6% and 15.5% in R1 (p<0.001). 93.7% of people who received a gFOBT from their GP actually completed it in R2 vs. 81.6% in R1 (p<0.001). The rate of ≥ 10 mm adenomas did not differ between R1 (32.9%) and R2 (30.5%). The positive predictive value for advanced neoplasia was significantly lower in R2 (28.3%, p=0.04) and in people who had a previous negative gFOBT result (27.2%, p=0.01) than in R1 (31.1%). The rate of invasive cancers limited to the colorectal wall was not different between R2 (59.3%) and R1 (69.4%).


Conclusion        

Participation and diagnostic yield deteriorated with time in our organized population-based gFOBT CRC screening program. Despite an increasing involvement of GPs, more than a quarter of eligible people did not repeat screening in the 2nd round. This deterioration was not observed in previous RCTs on gFOBT screening and may question the reproducibility of their effectiveness on the reduction of CRC mortality in the real world.



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