The Importance of Identifying Iron Deficiency Anaemia in the Early Detection of Colorectal Cancer.

Abstract

Colorectal cancer (CRC) is common and carries a relatively poor prognosis. The strong relationship between tumour stage at diagnosis and survival is the basis of the English Bowel Cancer Screening Programme (BCSP) and highlights the importance of early diagnosis. Iron deficiency anaemia (IDA) is also common. About 10% of cases in males and post-menopausal females are due to underlying gastro-intestinal (GI) cancer, most commonly CRC - and IDA is often the first manifestation. This thesis examines the detailed relationship between IDA and CRC. Chapters 4 and 5 describe the analysis of four large IDA datasets, confirming the prevalence of GI cancer, and demonstrating that cancer risk can be predicted from four simple, objective clinical indicators. This IDIOM model proved robust on internal and external validation. This research is valuable for patient counselling, targeting the investigation of high-risk individuals and (perhaps) avoiding invasive investigation in ultra-low risk cases. Chapter 6 outlines the analysis of a subset with recurrent IDA, suggesting that the subsequent risk of GI cancer is higher in those who were incompletely investigated the first time around. Chapter 7 describes the development of the IDIOM App. This is a freely available web-tool which allows cancer risk in IDA to be calculated within seconds, lending itself to clinical usage. Chapters 8 and 9 report the analysis of a large CRC database, demonstrating that diagnosis through the IDA pathway (1) generates as many cases as the BCSP; (2) identifies a distinct sub-population with a predominance of right- sided lesions; and (3) like the BCSP, is associated with a favourable tumour stage profile. The findings suggest that identifying iron deficiency anaemia could play an important role in the early diagnosis of CRC.