Introduction Colorectal cancer screening is based on early detection of cancers and removal of premalignant polyps though this adenoma to carcinoma sequence is thought to progress over several years. The Bowel Screening Programme in Wales based on guaiac FOBt and colonoscopy for individuals resting positive began roll-out in October 2008, with the aim of reducing mortality through cancer detection at an early stage. The aim of this study was to investigate whether screen detected cancers in Cardiff and the Vale of Glamorgan demonstrated any shift in the stage of cancer during the first three years of screening (initial prevalent round).
Methods Data was collected prospectively to compare the staging of colorectal cancer diagnosed in the BCSP with cancers diagnosed in the non-screening population in the same geographical region from 1st October 2008 to 31st December 2011. All information was cross checked with Cancer Registry data.
Results Screen detected cancer was found in 69 individuals (44 male, 25 female), with a positive predictive value of colonoscopy (after positive FOB testing) of 8.7%. Complete clinical staging was available for all 69 individuals; two patients did not undergo surgical resection due to the presence of metastases after radiological staging. There were 696 non-screening detected cancers during the same time period. For the purposes of this analysis, polyp cancers (cancer that was removed by endoscopic means at the time of colonoscopy/flexible sigmoidoscopy) were included in Duke’s stage A, except for one polyp cancer that required subsequent surgical resection and was staged as Duke’s C1. The results are shown in table 1. Three-quarters of cancers diagnosed in the BCSP were Dukes A or B, compared to 44.1% in the non-screening population. Of Duke’s D cancers, only 2.8% were diagnosed through screening, with 27% diagnosed in the non screening population (p < 0.0001).
Conclusion This data strongly supports significant stage shift of colorectal cancer even within the initial prevalent round in this single Bowel Cancer Screening centre in Wales that the benefits of screening may be demonstrable in outcomes at a relatively early stage of the programme.
Disclosure of Interest None Declared.
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