Investigations
Your Organisational Guidance
ebpracticenet urges you to prioritise the following organisational guidance:
Cancer du côlon : diagnostic, traitement et suiviPublished by: KCELast published: 2014Dikkedarmkanker: diagnose, behandeling en follow-upPublished by: KCELast published: 20141st investigations to order
full blood count
Test
Baseline in assessment of the patient and to assess for future treatments.
Between 6% and 10% of patients referred for investigation of iron-deficiency anaemia are found to have colorectal cancer, most commonly on the right side of the colon.[3][112][113] Almost 90% of patients with right-sided colorectal cancer have anaemia at diagnosis.[150]
Result
anaemia or normal
liver biochemistry
Test
Baseline in assessment of the patient and to assess for future treatments.
Result
normal, often even when liver metastases present
renal function
Test
Baseline in assessment of the patient and to assess for future treatments.
Result
normal, except if advanced pelvic disease is compressing ureters
quantitative faecal immunochemical test
Test
The UK guidelines recommend offering FIT in primary care settings to detect people likely to have colorectal cancer, so as to prioritise them for referral to secondary care.[111][138] FIT Symptomatic Opens in new window If the FIT result is ≥10 micrograms of haemoglobin/g of faeces, refer patients urgently. If colorectal cancer is suspected, give safety-netting advice and do not delay referral even if people do not return a faecal sample or have a FIT result of <10 micrograms of haemoglobin/g. Based on FIT results, investigations such as colonoscopy can be avoided in people who are less likely to have colorectal cancer, thus making the resources available to those who need them the most.[111][138]
Result
a FIT result of ≥10 micrograms of haemoglobin/g of faeces suggests urgent referral to secondary care (schedule an appointment within 2 weeks)
colonoscopy
Test
The preferred investigation, providing there is no clinical evidence of impending intestinal obstruction that would contraindicate administration of bowel preparation and insufflation of the colon.[115] It is the most sensitive diagnostic test for colorectal cancer and allows for biopsy of suspicious lesions and removal of incidental polyps.
Colonoscopy requires full bowel preparation with oral laxatives to ensure clear views of the whole of the mucosa.
Multiple biopsies are required for histological confirmation.
Colonoscopy is highly operator dependent. Completion rates (i.e., scope passed to the caecum) vary substantially, and a rate of 90% is considered acceptable. Many individuals achieve rates of 98%. Incomplete colonoscopy and poor bowel preparation are two of the variables contributing to a miss rate of 2% and 6%, respectively, for colorectal cancer at colonoscopy.[116]
Other procedural risks are related to sedation and colonic perforation (up to 0.12%).[117][118]
In prospective comparative studies, conventional colonoscopy is as acceptable to patients as virtual colonography, and both are preferable to double-contrast barium enema.[121][122] Computer-aided detection systems may be used for polyp detection during colonoscopy which may increase detection rates and reduce adenoma miss rate.[151][152]
Result
ulcerating or exophytic mucosal lesion that may narrow the bowel lumen
CT colonography
Test
CT colonography (virtual colonoscopy) provides an endoluminal view of the colon similar to traditional colonoscopy. It has equal sensitivity to conventional colonoscopy for the detection of colorectal cancer and does not require sedation, but has less specificity.[114][126][127] Both CT colonography and optical colonoscopy are considered to be more sensitive than barium enema; patients appear to prefer CT colonography to double-contrast barium enema.[123][124][125]
CT colonography can be used to complete colonic assessment when optical colonoscopy cannot be completed because of technical reasons such as a tortuous colon or stenosis. It can also be used to assess patients who are unwilling to undergo colonoscopy, who are not suitable candidates for colonoscopy, or for whom colonoscopy is contraindicated.
Full mechanical bowel preparation, as required for a colonoscopy, is needed for adequate CT colonographic evaluation.
Result
appearances similar to conventional colonoscopy, with an ulcerating exophytic mucosal lesion that may narrow the bowel lumen
CT scan of chest, abdomen, and pelvis
Test
All patients with colorectal cancer should have preoperative staging by CT scanning of the chest, abdomen, and pelvis to determine the local and distal extent of disease and to guide treatment and discuss prognosis.[129]
CT is performed with oral and intravenous contrast unless contraindicated; intravenous contrast is not required for chest CT but is usually given if performed in conjunction with abdominal CT.[129]
Patients presenting as an emergency with large bowel obstruction should also have a CT scan if possible because it aids management (e.g., a colonic stent may be more appropriate with multiple liver metastases, where resection of the primary tumour would not alter prognosis).
The main role of CT scanning is to detect distant metastases; it is an inaccurate method for assessing malignant lymphadenopathy or the depth of tumour invasion within the bowel wall.[153] Patients with liver metastases can be selected for resection based on the segments of liver involved, percentage of liver involved, and absence of involvement of major arteries or veins.
Result
colonic wall thickening, enlarged lymph nodes, liver metastases, ascites, lung metastases
genetic testing
Test
US and UK national guidelines recommend that all patients who are diagnosed with colon or rectal cancer are tested for Lynch syndrome.[129][139][140]
Test results may inform choice of systemic therapy, cancer risk reduction strategies in other sites, and testing of family members.
All patients with metastatic colorectal cancer should have tumour genotyped for RAS (KRAS and NRAS) and BRAF mutations individually or as part of a next-generation sequencing panel.[129][139] Testing should be performed only in certified laboratories.
Result
microsatellite instability/mismatch repair gene mutation detected in Lynch syndrome
Investigations to consider
MRI pelvis: rectal cancer protocol
Test
MRI is the preferred modality for local staging for rectal cancer due to its accuracy for determining both circumferential resection margin and T stage of the primary tumour.[130]
Accurate staging of rectal cancer is essential for selecting candidates for sphincter-preserving surgery, and identifying those who would benefit from neoadjuvant treatment. High-resolution pelvic MRI is recommended preoperatively in patients with rectal cancer to determine the depth of tumour invasion and to visualise tumour involvement of the mesorectal fascia (the circumferential resection margin).[154]
MRI also assesses perirectal nodal involvement.
Result
tumour invasion of mesorectal fascia
transrectal endoscopic ultrasound
Test
Necessary if MRI is contraindicated.
Transrectal endoscopic ultrasound (TRUS) provides a local (T and N) stage for rectal cancers, which is used to help direct treatment choice.[129]
TRUS is superior to CT scanning for the clinical T staging of rectal cancer.[155]
Result
enlarged perirectal lymph nodes indicate malignant involvement; invasion through the submucosa and into muscularis propria identifies a T2 tumour and extension of tumour into perirectal space identifies a T3 tumour
biopsy
Test
Colon and rectal cancer should be confirmed by histology.[115][128]
The vast majority of colorectal cancers are derived from colonic epithelial cells and are adenocarcinomas.
Result
confirms the diagnosis with characteristic pathological appearances; the degree of tumour differentiation (i.e., well, moderate, or poorly differentiated) will also be reported
carcinoembryonic antigen
Test
Carcinoembryonic antigen (CEA) levels should only be measured after confirmation of the diagnosis of colorectal cancer. CEA testing is not sufficiently sensitive or specific to be used for diagnosis in symptomatic patients, or as a screening tool in the asymptomatic population.[156]
Many patients are routinely followed up with CEA testing to detect recurrent colorectal cancer following surgical and adjuvant treatment, but evidence suggests that CEA is insufficiently sensitive to be used alone in this setting.[157][158]
Result
elevated; normal range for CEA in an adult non-smoker is <2.5 micrograms/L (<2.5 nanograms/mL) and for a smoker <5.0 micrograms/L (<5.0 nanograms/mL); reference range may vary between laboratories depending on assay
PET scan
Test
Specific indications include detection of extrahepatic metastases in patients thought to have liver-only metastatic disease in whom surgical metastasectomy is being considered.[131][132][133]
PET may help to localise disease recurrence in patients in whom this is suspected on the basis of symptoms or a rising carcinoembryonic antigen, but in whom the conventional imaging diagnostic work-up is negative.[135][136][137]
Result
focal areas of increased uptake of 18-fluoro-2-deoxyglucose detects metabolic changes of malignancy
Emerging tests
advanced optical imaging techniques
Test
Narrow-band imaging colonoscopy and magnifying chromoendoscopy may reduce the risk of performing piecemeal resection for T1 colorectal cancer, or unnecessary surgical referral for lesions amenable to endoscopic resection.[159] These techniques are not currently widely used.
Result
optical diagnosis of T1 colorectal cancer and T1 colorectal cancer with deep submucosal invasion
blood-based tests
Test
Blood-based tests (also known as liquid biopsy) have been developed in recent times to aid colorectal cancer screening.[141][142] Studies comparing blood-based tests with established diagnostic tests such as FIT found that blood-based tests were less sensitive and expensive.[143][144] Blood-based testing may be performed over no screening but should not replace the existing tests. The Septin 9 blood test is the only FDA-approved test for serum colorectal cancer screening in adults who refuse testing with other tests endorsed by the US Preventive Services Task Force.[145] None of the guidelines endorse this test for routine colorectal cancer screening.[145]
Result
Earlier detection of colorectal cancer without the stigma of stool testing
circulating tumour DNA
Test
Studies suggest circulating tumour DNA (ctDNA) can predict recurrence of colorectal cancer after surgery and can be used as a predictive biomarker in patients receiving immune checkpoint inhibitors.[160][161][162][163][164][165][166][167] Post-surgery presence of ctDNA may be indicative of recurrence, while absence may indicate no recurrence.[160] As the available evidence is inadequate, routine ctDNA testing assays are not recommended by the National Comprehensive Cancer Network (NCCN).[129][139] Dose de-escalation based on ctDNA results is not recommended.[129][139]
Result
Post-surgery presence of ctDNA may be indicative of recurrence
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