The Use of Symptoms to Predict Colorectal Cancer Site


but cannot be used to predict the cancer site. Unfortunately, rectal bleeding is also associated with many other conditions affecting the distal colon and rectum (such as haemorrhoids and diverticular disease), and subsequently has an overall low positive predictive value (PPV) for colorectal cancer.16,17


cancer,15 symptoms significantly reduces the odds of cancer,18


The presence of peri-anal but distal benign


conditions should not exclude the need for endoscopic evaluation as synchronous neoplastic lesions are well recognised.1


Overall, rectal


bleeding is clearly associated with left-sided colonic disease, and as such the National Institute for Clinical Excellence (NICE), UK advocates investigation of rectal bleeding (without associated ‘right-sided symptoms’) to be a flexible sigmoidoscopy to 60cm.19


Change in Bowel Habit


A change in bowel habit has a poor predictive value for colorectal cancer,15


but is clearly more common in left-sided cancers.7,8 Studies


have suggested that patients with a change in bowel habit (with or without rectal bleeding) and no additional symptoms should be initially investigated with a flexible sigmoidoscopy.20


National Institute


of Health and Clinical Excellence (NICE) guidelines advocate that further investigations should be performed only in patients with persistent symptoms.19


Constipation is universally recognised as a


symptom associated with distal cancers, as stool entering the proximal colon is liquid. However, studies have shown the incidence of colorectal cancer in patients with constipation is equal to the incidence seen in screening of asymptomatic patients.21


If new-onset


constipation is to be investigated, it should be considered a symptom of left-sided disease, as Majumdar et al. have identified constipation as an independent predictor of distal location.22


A bowel habit varying


between constipation and diarrhoea has a lower PPV than constipation alone.23


Rectal Symptoms and a Change in Bowel Habit Patients rarely present with a single symptom, and a combination of symptoms can give greater accuracy in predicting colorectal cancer site. Thompson et al. produced extremely strong data that clearly clarify rectal bleeding and a change in bowel habit to be symptoms associated with left-sided cancer.24


In patients presenting with rectal


bleeding and/or a change in bowel habit, less than 0.2% will have a cancer proximal to the sigmoid colon. This is equal to 1:1,895 in patients <60 years of age and 1:250 in patients 60 years of age or over, which is little or no higher than the incidence of proximal cancers diagnosed when screening asymptomatic patients with total colonoscopy.24


Majumdar et al. describe a ‘distal cluster’, referring to a combination of symptoms associated with distal colorectal cancer: rectal bleeding, altered stool and one of diarrhoea, mucus, rectal pain or tenesmus.22


Anaemia


Anaemia is clearly associated with colorectal cancer, with the PPV increasing with age and with each 1g/dl reduction in haemoglobin.25 This anaemia is due to iron deficiency,26


anaemia is poorly associated with colorectal cancer, as opposed to other colonic diagnoses.27


more common finding in right-sided lesions,12,20,26,28


Multiple studies have found anaemia to be a with haemoglobin,


ferritin and iron levels all being lower in right-sided cancers.29 Furthermore, distal lesions have a higher haemoglobin than right-sided cancers.22


Total colonoscopy or whole colonic imaging is required to exclude cancer in patients with iron-deficiency anaemia, with a number needed to investigate (NNI) to diagnose one cancer of 13.30


EUROPEAN GASTROENTEROLOGY & HEPATOLOGY REVIEW and non-iron-deficiency


Flexible sigmoidoscopy – passing to the splenic flexure, with good bowel preparation


Anaemia in colorectal cancer is primarily caused by blood loss, with a clear correlation between increasing anaemia and increasing tumour stage31


and mortality.32 diagnosed at a more advanced stage,6


Right-sided cancers have been shown to be and the longer period of occult


blood loss may explain the increased incidence of anaemia. Faecal Occult Blood


Many countries have commenced colorectal cancer screening programmes. In England and Wales, the NHS screening programme consists of faecal occult blood testing for all patients 60–74 years of age. Patients positive for faecal occult blood are subsequently offered a total colonoscopy. Results from screening programmes have shown that asymptomatic patients with positive faecal occult blood test who are diagnosed with colorectal cancer have approximately 30% of cancers in the right side of the colon.33


This is a similar distribution


of colorectal cancer to that seen in symptomatic patients. Patients undergoing cancer screening often have unrecognised GI symptoms which they have not told their doctor.34


Although these symptoms are


not the reason for colonoscopy, they are likely to be related to the site of any colorectal cancer subsequently diagnosed.


Obstruction and Perforation


Colonic obstruction is the most common complication from colorectal cancer, and significantly increases the risk of perforation. Subsequently, the five-year survival for obstructing lesions is worse than in patients undergoing elective treatment of their colorectal cancer,35


increased incidence of metastases.37


often related to more advanced disease at presentation36 Some studies have confirmed


or


that colorectal cancer associated with colonic obstruction or perforation has a far lower incidence in the rectum.37,38 is not consistent with all studies.12


been shown to occur more commonly with left-sided tumours,8 the greatest incidence in the sigmoid colon.36


Obstructing lesions


in the right colon have a reduced disease-free survival compared with obstructing lesions of the left colon.39


more common in obstructing colorectal cancer.40


Also, synchronous lesions are Thus, as obstruction


109 However, this


Obstruction and perforation have with


No Yes Colonoscopy Blood count


Iron-deficiency anaemia?


Figure 1: Algorithm for Investigation of Colorectal Cancer Symptoms


Distal symptoms alone Change in bowel habit Rectal bleeding Tenesmus Rectal pain


Proximal symptoms Weight loss


Abdominal mass Abdominal pain Anorexia


Nausea and vomiting ± distal symptoms


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