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Original research
Colorectal cancer and the blood loss paradox
  1. Orouba Almilaji1,2,
  2. Sally D Parry1,
  3. Sharon Docherty2,
  4. Jonathon Snook1
  1. 1Department of Gastroenterology, Poole Hospital, UHD Foundation Trust, Poole, UK
  2. 2Department of Medical Science and Public Health, Bournemouth University, Bournemouth, UK
  1. Correspondence to Dr Jonathon Snook, Poole Hospital NHS Foundation Trust, Poole, UK; jonathon.snook{at}gmail.com

Abstract

Background Faecal occult blood (FOB) positivity and iron deficiency anaemia (IDA) are common manifestations of colorectal cancer (CRC) and both potentially facilitate diagnosis at an earlier, more treatable stage. It has been assumed that both are the consequence of low-grade blood loss from the tumour bed.

Method A retrospective analysis of 1121 cases of CRC diagnosed at a single centre between 2010 and 2016, comparing cases presenting via FOB-based Bowel Cancer Screening Programme (BCSP) and IDA pathways for a series of variables including age, sex, tumour location and prevalence of anaemia.

Results The BCSP and IDA pathways each accounted for about 15% of the total case load. There were significant differences between the BCSP and IDA sub-groups in median age (68 vs 78 years: p<0.001), median haemoglobin (138 vs 89 g/L: p<0.001) and proportion of lesions in right colon (31.1% vs 82.5%: p<0.001). The major disparity in the prevalence of anaemia (overall 20.0% vs 98.2%: p<0.001) persisted when controlled for tumour location.

Conclusion Paradoxically, CRC screening through the detection of FOB positivity and IDA identifies distinctly different sub-populations of cases. The theoretical implication is that an additional mechanism may be required to explain the development of IDA in CRC. The practical implication is that detection of IDA may have a complementary role to the BCSP in population screening for CRC.

  • colorectal cancer
  • iron deficiency

Data availability statement

Data are available upon reasonable request.

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Data availability statement

Data are available upon reasonable request.

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Footnotes

  • Contributors OA, SDP and JS conceived and designed this study. OA analysed the data and drafted the manuscript. All authors made significant contributions to the subsequent revision of the paper and approved the final version, and JS is the guarantor.

  • Funding PhD studentship (OA) jointly funded by Poole Hospital Gastroenterology Research fund and Bournemouth University.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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