According to NICE (2018), 40,000 people are newly diagnosed each year with colorectal cancer. It is the “fourth most common cancer in men and the third most common cancer in women worldwide” (Center, Jemal and Ward, 2009). Incidence is much higher in males than in females and strongly increases with age, in northern and western Europe (Ferlay et al., 2010). Occurrences are low at ages younger than 50 years, but strongly increases with age- the median age at diagnosis is about 70 years (Siegel et al., 2012).
Colorectal cancer is the term used to cover cancers found in the colon and the rectum, it is characterised by uncontrolled growth of cells forming a lump called the primary tumour (Nice.org.uk, 2018). Each time the colon cells divide, the more mutations occur and the higher the risk of cancer is. The mutated cells build up on the surface of the colon and form a lump that appears as a polyp. As this is a slow process, it is possible to find and remove the polyp “while they are still in the benign or precancerous stage” (Health Essentials from Cleveland Clinic, 2018).
In this essay, I will be discussing Ann’s imaging and management pathway from her GP appointment, Flexible sigmoidoscopy (FS), Computed Tomography Colonography (CTC), Computed Tomography (CT) staging scan and Colonoscopy. This essay will also cover possible treatments and follow up for colorectal cancer (CRC). The following figure is a summary of her start to the pathway:
Diagnostic imaging prior to any possible treatments is needed to confirm the presence of cancer in the bowel. Prompt imaging is necessary as if left untreated Ann’s symptoms could worsen which is why the two week wait pathway was essential in Ann’s case. Figure 2 shows the percentage of colorectal cancer diagnoses by presentation route by year of diagnosis, 2006-2013.
GP consultation
Ann notified her GP of weight loss and a change in bowel habit. The main symptoms of colorectal cancer are: blood in the stools, a persistent change in bowel habit and lower abdominal pain which may be associated with unintentional weight loss. According to NHS.UK (2018), these symptoms could also be indicative of other health problems. For example, Haemorrhoids may be the cause of blood in the stools or a change in bowel habit could be as a result of something previously eaten or something that could easily be resolved using laxatives. This is why it is vital to use imaging modalities to give correct diagnoses.
In order to detect the blood in stool samples, a faecal immunochemical test was carried out. According to Daly (2012), the test has a “higher sensitivity and specificity for the detection of cancer than guaiac-based tests” as they use antibodies specific to human globin. As the globin component degrades as it travels through the GI tract so the test is less likely to detect any globin from upper GI bleeding which is vital in detecting cancer in the lower GI tract (Nice.org.uk, 2017). Ann’s abnormal result meant further testing via a colonoscopy/flexible sigmoidoscopy. NICE guidelines recommend a 2 week wait pathway if the patient’s test shows occult blood in their faeces, is over 60 years, has unexplained weight loss and changes in bowel habit- Ann met the criteria for a suspected cancer pathway referral.
A Carcinoembryonic Antigen (CEA) test was also taken to see if the symptoms stated indicate the presence of CRC. CEA is made by cancerous tumour cells; the test measures the amount present in the blood. The doctor placed a needle into a vein to draw out blood. Levels of CEA higher than 20 ng/Ml indicates the presence of cancer however it can also be indicative of inflammatory bowel disease, liver disease or other conditions. In Ann’s test result the inflammatory markers were not raised however this could have been due to the stage of her cancer as the sensitivity of the marker increases with tumour stage (Hauptman and Glavač, 2017). According to Nbt.nhs.uk (2012), due to the low sensitivity and specificity of the CEA test for early disease it isn’t recommended for screening or diagnosis of CRC.
The GP also checked to see if Ann had iron deficiency anaemia through a red blood cell (RBC) count which allowed a sample of blood to be examined. RBC counts vary depending on gender, for a woman the normal range would 4.2 to 5.4 million cells/mcL (nhs.uk, 2018). A patient can have colorectal cancer leading to a lack of iron due to bleeding from the cancer and not show any symptoms of anaemia. According to Khanbhai et al. (2014), anaemic patients with cancer show reduced survival rates and quality of life which is why in Ann’s case a two-week wait pathway was crucial.
Flexible Sigmoidoscopy
A colonoscopy is preferred, however, as Ann is more likely to have “significant co-morbidity” the flexible sigmoidoscopy is used (Todd, W.Groundwater and H.Gill, 2017). Flexible sigmoidoscopy is a screening tool for cancerous or pre-cancerous polyps only in the distal colon and rectum. A 60cm long flexible fibre optic tube known as a sigmoidscope is inserted in the anus- it contains a small light and a camera which is used whilst examining the rectum and colon to take images of the bowel lining. The scope pumps air into the large bowel to enhance the quality of the images. The scope is withdrawn when the scope reaches the transverse colon. Prior to the examination, laxatives were given to clear the large bowel and on the morning of the examination a saline enema was given to clear the rectum.
Doctors can help find the cause of unexplained symptoms like bleeding, changes in your bowel activity and unexplained weight loss via flexible sigmoidoscopy. If there are any abnormal areas seen, biopsies can be taken to determine what the cause is. In Ann’s case, the flexible sigmoidoscopy procedure was inconclusive. However, this is very common as elderly women have an increased risk of inadequate flexible sigmoidoscopy procedures (“Concerns and challenges in flexible sigmoidoscopy screening” Colorectal cancer vol. 1,4 (2012): 309-319., 2012). There are several reasons for a failed FS including female gender, older patients, prior abdominal surfery and poor bowel preparation (Bortz, 2014). As a result, we used other imaging modalities to make an accurate diagnosis of colorectal cancer. Figure X highlights the trend between an inconclusive FS and age and gender.
Computed Tomography Colonoscopy (CTC)
CT Colonography is an examination for the screening of the large intestine for cancer and polyps using CT scans. CTC is designed to detect polyps before they become cancerous and to detect cancers that have already developed. According to a systematic review of published CT Colonography studies assessing lesion detection in elderly patients, CTC sensitivity for colorectal cancer was 93% in senior-age patients (Pickhardt et al., 2018). A CTC was chosen as it allowed the areas that were not covered in the flexible sigmoidoscopy to be examined thoroughly and identify any hidden polyps. Ann also chose to have a CTC instead of a colonoscopy due to the procedure being non-invasive, not involving sedation/anaesthesia and ability to identify abnormalities outside the colon. A multicentre study found that of 441 patients that had undergone both CTC and colonoscopy, 77.1% preferred CTC and 13.8% preferred colonoscopy. In addition, 92.9% of the patients labelled their experience with CTC as “excellent” (Screening CT Colonography: Multicentre Survey of Patient Experience, Preference, and Potential Impact on Adherence, 2012).
Prior to the scan, an antispasmodic agent such as Buscopan was given to relax the bowel wall smooth muscles minimising peristalsis immediately. It reduced bowel peristalsis which reduces movement unsharpness in the images. Some studies have shown that colonic distension is better in patients who had received antispasmodic compared to those that didn’t (Bortz, Ramlaul and Munro, 2016).
Accurate detections of small polyps during CTC is dependent upon the bowel preparation- CT Colonography is performed on an empty bowel. Two days prior to the exam, a low fibre and light diet is required. Ann was given a leaflet filled with all the information on what her diet should consists of, what she should do for bowel preparation, how to ingest picolax and gastrograffin etc. which are all vital prior to the examination (see Appendix A). A sachet of Picolax and a bottle of Gastrografin is given to improve the quality and sensitivity of the examination. Picolax is a laxative and Gastrograffin is a liquid designed to allow us to clearly define faeces in the colon. The Sodium Picosulfate element in Picolax is used to empty and cleanse the bowel by stimulating the nerve endings in the walls of the colon and rectum which increases the muscle contractions and allows contents to move through and be emptied. The Magnesium citrate element is used as a laxative so it increases the water content to help wash out the bowel. Figure X shows how effective Gastrograffin is with bowel preparation for the examination. Gastrograffin is a contrast medium containing iodine used in faecal tagging. It has the effect of staining residual fluid white aiding in 2D evaluation of polyps and it emulsifies stool causing a secondary cleanse of the bowel (Bortz, 2014). The presence of faecal residue can hide pathology and produce false positives or false negatives which is why positive contrast media is mandatory in order to distinguish polyps and lesions from faecal material (Computed tomography Colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications, 2016).
For the CTC, Ann was put in the left lateral decubitus position and after lubrication a rectal catheter was inserted. A thin and flexible rectal catheter was used for the insufflation of the colon by 3-4 litres of carbon dioxide to expand the colon to permit better visualization of the colon. A CT scout image in supine position was taken to check the distension before starting the CT examination. Figure A shows what we are looking to see in the CT scout image. A Topogram helps rule out the presence of severe stenosis with risk of perforation. Bowel distension should be considered as adequate if the luminal surface of each colonic segment can be visualised (Computed tomography Colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications, 2016).
A combination of supine and prone positions were taken to improve the evaluation of the colon and increase the sensitivity for the detection of polyps which may have been attached to the bowel walls from fluid or faecal residue (Fig. X). The figure below highlights the importance of using supine and prone projections.
From the CTC examination, the Doctor found a 5mm polyp in Ann’s ascending colon thus Figure X is similar to what was seen in Ann’s images. In comparison to a normal CT scan of the abdomen (see Figure X), there should be a smooth outline of the large bowel with no dense masses attached to the colon wall. The polyp appears light grey due to its soft tissue density which allows it to be identified in the colon. The difference between the distension of the colon can also be seen in both images.
CTC allows 2D axial images and 3D visualisation offering an endoluminal view acting as complementary modalities (Fig. X). 3D visualisation magnifies lesions making detection much easier however they are largely dependent on the distension and the removal of residual material. It also allows the biopsies via colonoscopy to be done much quicker as the exact location is known.
Buscopan’s side effects include blurred vision and a dry mouth however they dissipate after 20 minutes. Ann was recommended to drink plenty of fluids for the following 2-4 days. The CO2 used for distention is absorbed quickly and causes minor abdominal discomfort for 1-2 hours. Ann was told to return to her normal eating and drinking patterns and was advised to contact her GP If she experienced any severe symptoms after the examination.
CT scan of Chest, Abdomen and pelvis
NICE guidelines state that for colorectal cancer, a CT of the Chest, Abdomen and pelvis must be taken to determine any spread to other organs. The CT scan can then be assessed to pinpoint the location of any possible metastases. Ann was fully informed about the CT scanning procedure in a leaflet containing information on the scan, the preparation required and the aftercare (see Appendix B).
Prior to the scan, Ann was told not to eat or drink in order to maximise the effectiveness of the contrast material being used. After the three-point patient identification check, the radiographer who administered the contrast medium and performed the procedure explained the steps and answered any questions Ann had about the examination. The radiographer made sure that Ann understood the procedure, risks, instructions and verbally agreed to proceed. One radiographer cannulated Ann and the other set up the iodine-based contrast media so the contrast material was injected intravenously.
The CT scan found no evident metastases which, according to the TNM staging system, meant Ann’s cancer was N0 and M0.
Colonoscopy
As a biopsy cannot be done during the CT colonoscopy, a regular colonoscopy must be carried out. One study found that that CTC missed 1 of 29 colorectal cancers and colonoscopy missed none of 55 patients (Computed tomographic Colonography versus colonoscopy for investigation of patients with symptoms suggestive of colorectal cancer (SIGGAR): a multicentre randomised trial, 2013). Carrying out the colonoscopy allowed a biopsy to be taken quickly as the location was known due to the CTC. This meant that for Ann the procedure wasn’t long and as uncomfortable as it would’ve been without the information from the CTC.
A colonoscopy examines the whole large bowel which is why this was carried out after a flexible sigmoidoscopy was done. An endoscopist inserts a colonoscope, with a light and camera at one end, into the rectum and passes it through the bowel. Gas is also inserted into the bowel to make the bowel lining easier to see. A review showed that there is a 90% improvement in the rate of detection of small polyps using chromoscopy (Chromoscopy versus conventional endoscopy for the detection of polyps in the colon and rectum (Review), 2016). According to Cancerresearchuk.org (2018), a chromoscopy is a dye that is sprayed onto the lining of the bowel to highlight any abnormalities in that region. The endoscopist will decide where to take samples of tissues from the colon to conduct a biopsy.
A biopsy involves examining a sample of tissue under a microscope to assess any abnormalities and, if confirmed, determine what grade the cancer may be. Once a diagnosis of colorectal cancer is confirmed, it must then be staged to help determine which treatment is the most appropriate. Staging also helps decide whether pre-operative chemo-radiotherapy is needed to shrink the tumour. In Ann’s case it was Grade 1/Stage 1 where the cancer cells grow slowly and look similar to normal cells- the cancer grew through the superficial lining of the colon but hasn’t spread beyond the colon wall. Using the TNM (Tumour, Nodes and Metastases) staging system, Ann’s cancer characteristics are the following:
1) T2= Tumour grew into the muscle layer of the bowel wall
2) N0= no lymph nodes found to contain cancer cells
3) M0= No cancer spread to other organs
Treatment and Follow up
As a polyp was found in Ann’s ascending colon, it had to be removed through colonoscopy. The cancerous part of the colon is removed alongside a small area of the healthy tissue adjacent to the cancerous tissue in this procedure. Ann did not need to have chemotherapy after the procedure as she had very early bowel cancer.
According to NICE (2014), patients should be offered regular surveillance with “a minimum of two CTs of the chest, abdomen and pelvis in the first 3 years” and “regular serum carcinoembryonic antigen tests”. A surveillance colonoscopy is also required 1 year after treatment. Patients diagnosed at stage I have a higher one-year net survival rate than those diagnosed at stage IV (Cancerresearchuk.org, 2014). Figure X shows 98% of female patients diagnosed at stage I survived their disease for at least one year.