Clinical features of colorectal cancer before diagnosis: a population-based case–control study

Abstract

Most colorectal cancers are diagnosed after the onset of symptoms. However, the risk of colorectal cancer posed by particular symptoms is largely unknown, especially in unselected populations like primary care. This was a population-based case -control study in all 21 general practices in Exeter, Devon, UK, aiming to identify and quantify the prediagnostic features of colorectal cancer. In total, 349 patients with colorectal cancer, aged 40 years or more, and 1744 controls, matched by age, sex and general practice, were studied. The full medical record for 2 years before diagnosis was coded using the International Classification of Primary Care-2. We calculated odds ratios for variables independently associated with cancer, using multivariable conditional logistic regressions, and then calculated the positive predictive values of these variables, both individually and in combination. In total, 10 features were associated with colorectal cancer before diagnosis. The positive predictive values (95% confidence interval) of these were rectal bleeding 2.4% (1.9, 3.2); weight loss 1.2% (0.91, 1.6); abdominal pain 1.1% (0.86, 1.3); diarrhoea 0.94% (0.73, 1

The mortality of colorectal cancer in relation to the initial symptom at presentation to primary care and to the duration of symptoms: a cohort study using medical records

“…We studied subjects from a previously described population-based case -control study (Hamilton et al, 2005). In that study, all 358 primary colorectal cancer cases in patients aged 40 years or more from Exeter Primary Care Trust (PCT), diagnosed between 1998 and 2002, were identified from the local cancer registry.…”

“…The entire primary care record for the 2 years preceding diagnosis for all subjects was coded using the International Classification of Primary Care-2, (WONCA, 1998) although for this paper only data from the year before diagnosis were used. The second year before diagnosis was omitted because the rate of reporting of the various clinical features was similar in both cases and controls for that year, so reporting of features in that year by cases would probably be unrelated to their future cancer (Hamilton et al, 2005).…”

“…Ten clinical features had been identified as being independently associated with the diagnosis of colorectal cancer: rectal bleeding, abdominal pain, diarrhoea, constipation, weight loss, abdominal tenderness, anaemia (haemoglobin below 13 g dl À1 ), abnormal rectal examination, a blood sugar level over 10 mm l À1 , and a positive faecal occult blood testing (Hamilton et al, 2005). For this analysis, only the five symptoms and one investigation, anaemia, were included.…”

“…In the UK, approximately three-quarters of colorectal cancers present initially to their general practitioner (GP) with nonemergency symptoms, such as rectal bleeding, abdominal pain, or change in bowel habit (Barrett et al, 2006). Even after the proposed introduction of screening in the UK in 2006, it is likely that the majority of patients will still present with symptoms (Hamilton et al, 2005).…”

“…We sought to address these methodological issues by an analysis of a cohort of 349 patients with colorectal cancers occurring in a 5-year period from Exeter, Devon, UK (Hamilton et al, 2005). In this cohort, all symptoms recorded in primary care before diagnosis were collected and coded systematically.…”