Study snapshot

Who were involved? Approximately 7,472 men and women who were aged 55 years or over between March 2004 and December 2007 and were referred to one of the participating NHS hospitals with colorectal cancer symptoms at the time of the SIGGAR randomised controlled trials.

Locations: 21 NHS hospitals across England.

Dates: Registered between 2004 and 2007. Study closed 17 February 2022.

Overview

The Symptoms of Colorectal Cancer Evaluation Research (SOCCER) study was a clinical study using information collected on people who had symptoms of colorectal cancer and had been referred by their doctor for further tests.

The SOCCER study used data gathered during the SIGGAR trials to investigate the potential efficacy of flexible sigmoidoscopy as an alternative to whole-colon examination.

To fulfil the aims of SOCCER and understand the long-term effectiveness of the different examination techniques we tracked the long-term health outcomes of study participants.

SOCCER shares an International Standard Randomised Controlled Trial number with SIGGAR, 95152621.

The study was funded by the NIHR-HTA programme and Cancer Research UK.

Background

Patients with suspected colorectal cancer usually undergo colonoscopy. However, studies had shown that an examination of the distal colorectum using flexible sigmoidoscopy can be a safe and clinically effective investigation for some patients. Flexible sigmoidoscopy may be preferred if proximal colon cancer risk is low.

SOCCER aimed to investigate the links between patient symptoms at presentation and colorectal cancer risk by subsite, and to provide evidence of whether or not flexible sigmoidoscopy is an effective alternative to whole-colon investigation in patients whose symptoms do not suggest proximal or obstructive disease. It aimed to validate earlier findings investigating which patients could undergo flexible sigmoidoscopy alone.

Method

SOCCER was a multicentre retrospective study using data collected prospectively from two randomised controlled trials called the SIGGAR trials. Additional data were collected from trial diagnostic procedure reports and hospital records. Colorectal cancer diagnoses within 3 years of referral were sourced from hospital records and national cancer registries via the Health and Social Care Information Centre (now NHS England).

Data for the SOCCER study was collected from approximately 7,375 men and women who were:

  • Aged 55 years or over between March 2004 and December 2007.
  • Referred to one of the 21 participating English NHS hospitals with colorectal cancer symptoms at the time of the SIGGAR randomised controlled trials.
  • Registered as potentially eligible for the SIGGAR randomised controlled trials.

The SOCCER cohort included:

  • 5,345 people who were randomised and consented for SIGGAR; and
  • 2,030 people who had symptoms suggestive of bowel cancer but were not randomised to SIGGAR as a result of clinician preference. These patients were registered but eventually not randomised to the SIGGAR study.

We calculated yields and number of needed whole-colon examinations (NNE) to diagnose one cancer by symptoms/signs and subsite. We considered narrow (haemoglobin <11 g/dL men; <10 g/dL women) and broad (<13 g/dL men; <12 g/dL women) anaemia definitions and iron-deficiency anaemia (IDA).

The main outcome measure was diagnostic yield of CRC at distal (to the splenic flexure) and proximal subsites by symptoms/clinical signs at presentation.

Results

The dataset for analysis comprised of 7,380 patients, of whom 59% were women (median age 69 years, interquartile range 62–76 years). Change in bowel habit (CIBH) was the most frequently presenting symptom (73%), followed by rectal bleeding (38%) and abdominal pain (29%); 26% of patients had anaemia. Colorectal cancer was diagnosed in 551 patients (7.5%): 424 (77%) patients with distal colorectal cancer, 122 (22%) patients with cancer proximal to the descending colon and five patients with both proximal colon cancer and distal colorectal cancer. Proximal colon cancer was diagnosed in 96 out of 2021 (4.8%) patients with anaemia and/or an abdominal mass. The yield of proximal colon cancer in patients without anaemia or an abdominal mass who presented with rectal bleeding with or without a CIBH or with a CIBH to looser and/or more frequent stools as a single symptom was low (0.5%). These low-risk groups for proximal colon cancer accounted for 41% (3032/7380) of the cohort; only three proximal colon cancers were diagnosed in 814 low-risk patients examined by flexible sigmoidoscopy (diagnostic yield 0.4%).

A limitation to this study is that changes to practice since the SIGGAR trials ended, such as new referral guidelines and improvements in endoscopy quality, potentially weakened the generalisability of our findings.

Symptom profiles can be used to determine whether or not a whole colon investigation is necessary. Most proximal colon cancers were diagnosed in patients who presented with anaemia and/or an abdominal mass. In patients without anaemia or an abdominal mass, proximal colon cancer diagnoses were rare in those with rectal bleeding with or without a CIBH or with a CIBH to looser and/or more frequent stools as a single symptom. Flexible sigmoidoscopy alone should be a safe and clinically effective investigation in these patients.

A cost-effectiveness analysis of symptom-based tailoring of diagnostic investigations for colorectal cancer is recommended.

Results were published in 2017 in the British Journal of Cancer and can also be found in the NIHR-HTA Journals Library.