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Are there biological differences between screen-detected and interval colorectal cancers in the English Bowel Cancer
Elizabeth Walsh1, Colin J Rees2,3, Michael Gill2
1Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, St James's University Hospital, Leeds LS9 7TF, UK.
Background:
We measured biomarkers of tumour growth and vascularity in interval and screen-detected colorectal cancers (CRCs) in the English Bowel Cancer Screening Programme in order to determine whether rapid tumour growth might contribute to interval CRC (a CRC diagnosed between a negative guaiac stool test and the next scheduled screening episode).
Methods:
Formalin-fixed, paraffin-embedded sections from 71 CRCs (screen-detected 43, interval 28) underwent immunohistochemistry for CD31 and Ki-67, in order to measure the microvessel density (MVD) and proliferation index (PI), respectively, as well as microsatellite instability (MSI) testing.
Results:
Interval CRCs were larger (P=0.02) and were more likely to exhibit venous invasion (P=0.005) than screen-detected tumours. There was no significant difference in MVD or PI between interval and screen-detected CRCs. More interval CRCs displayed MSI-high (14%) compared with screen-detected tumours (5%). A significantly (P=0.005) higher proportion (51%) of screen-detected CRC resection specimens contained at least one polyp compared with interval CRC (18%) resections.
Conclusions:
We found no evidence of biological differences between interval and screen-detected CRCs, consistent with the low sensitivity of guaiac stool testing as the main driver of interval CRC. The contribution of synchronous adenomas to occult blood loss for screening requires further investigation.