Clinical Trial: Evaluation of Flexible Sigmoidoscopy Screening as an Adjunct to the National FOBT Screening Programme in Scotland

Study Status: Recruiting
Recruit Status: Recruiting
Study Type: Interventional

Official Title: Evaluation of Flexible Sigmoidoscopy Screening as an Adjunct to the National FOBT Screening Programme in Scotland - A Random Evaluation

Brief Summary:

Guaiac faecal occult blood testing (gFOBT) consistently demonstrates reductions in deaths from colorectal cancer of around 16% and gFOBT screening is now routine in all four countries of the United Kingdom. However, gFOBT has significant limitations and is associated with a substantial interval cancer rate in the region of 50 %, indicating a severe deficiency in sensitivity for cancer. Additionally, as the majority of colorectal cancers arise from pre-existing adenomas, it is important for colorectal screening programmes to detect adenomas in order to reduce the incidence of the disease as well as the associated mortality. Although gFOBT does detect some adenomas, most randomised trials have not demonstrated a reduction in colorectal cancer incidence. Also, FOBT screening tends to under-detect cancers in women and it is relatively insensitive for rectal cancer when compared with colon cancer.

Single flexible sigmoidoscopy (FS), between the ages of 55 and 65 years, has been shown to bring about a significant reduction in colorectal cancer mortality. In addition, and most importantly, after a period of four years a significant reduction in colorectal cancer incidence was observed. FS does not suffer from low specificity since false positives do not occur, and there is independent evidence that it is more sensitive than a single gFOBT. In addition, FS is ideally suited to detecting rectal cancers and adenomas, and it is unlikely that there would be a gender difference in the sensitivity.

Single FS has not been compared with biennial FOBT and there is no information regarding the utility of FS in a population that has already been exposed to FOBT screening. It is hypothesised that offering a combination of gFOBT and FS would provide an enhanced screening algorithm that would be associated with better outcomes than gFOBT alone.

Detailed Summary:

Screening for colorectal cancer is now being introduced in many countries worldwide, but there is still considerable uncertainty as to the ideal modality. Population based trials of guaiac faecal occult blood testing (gFOBT) have consistently demonstrated significant reductions in disease specific mortalities and three randomised population based trials of biennial gFOBT have demonstrated reductions in deaths from colorectal cancer of around 16%. As a result of these trials, a demonstration pilot was performed in the United Kingdom which has led to the introduction of gFOBT screening in all four countries of the United Kingdom.

However, gFOBT has significant limitations. It is clear that this form of screening is associated with a substantial interval cancer rate in the region of 50 %, indicating a severe deficiency in sensitivity for cancer. Furthermore, as it is now well established that the majority of colorectal cancers arise from pre-existing adenomas, it is important for any colorectal screening programme to detect adenomas in order to reduce the incidence of the disease as well as the associated mortality. Although gFOBT does detect some adenomas, the randomised studies have not demonstrated a reduction in colorectal cancer incidence with the exception of the Minnesota Study that used rehydrated gFOBT resulting in a high positivity rate and a large number of colonoscopies. It should be borne in mind however, that the newer faecal immunochemical tests (FIT), which, unlike gFOBT, are specific for human haemoglobin, perform better in terms of both cancer and adenoma detection.

It is also of interest that recent scrutiny of the interval cancer data from the Scottish demonstration pilot has clearly demonstrated that gFOBT screening tends to under-detect cancers in women when compared with men. In addition, it is relative
Sponsor: University of Dundee

Current Primary Outcome: Number of colorectal cancers or adenomas diagnosed [ Time Frame: Within duration of study - two years ]

Original Primary Outcome: Same as current

Current Secondary Outcome: Number of invited individuals undergoing flexible sigmoidoscopy [ Time Frame: Within duration of study - two years ]

Original Secondary Outcome: Same as current

Information By: University of Dundee

Dates:
Date Received: September 3, 2015
Date Started: June 2014
Date Completion: December 2016
Last Updated: September 24, 2015
Last Verified: September 2015