3.1 Specialist diagnostic work-up
The treatment team, after taking a thorough medical history and making a thorough medical examination of the patient, should undertake the following investigations under the guidance of a specialist.
Patients thought to have resectable or potentially curable disease should have routine blood tests (full blood count [FBC], urea and electrolytes [U&E], liver function tests [LFT], carcinoembryonic antigen [CEA]), a complete colonic assessment by colonoscopy, or virtual colonoscopy in the case of an impassable tumour plus the following, as clinically indicated:
For colon and rectal cancer:
- computed tomography (CT) scan of the chest, abdomen and pelvis
- if CT shows metastatic disease confined to the liver, MRI of the liver to assess for resectability
- PET-CT – this is recommended for patients who have suspicious metastatic disease at initial staging. It also recommended for restaging for those who have potentially resectable/treatable metastatic disease.
For rectal cancer:
- endorectal ultrasound to assess T1 and early T2 tumours in patients who may be appropriate for local resection techniques.
It is essential that the treating surgeon accurately assesses the tumour location.
Investigations should be completed within two weeks.
Between 10 and 15 per cent of colorectal cancers will present as an emergency. This necessitates appropriate acute care followed by management from a multidisciplinary team.
Between 1 and 5 per cent of colorectal cancers are specifically inherited (familial adenomatous polyposis and lynch syndrome) and up to 25 per cent may have some inherited component. The features that suggest a genetic predisposition may include:
- early age at onset
- multiple primary cancers
- multiple polyps
- the histological type of polyp(s)
- family history of similar or related cancers.
Universal testing for mismatch repair deficiency by IHC or MSI testing is now recommended as standard practice for treatment-related and familial risk assessments.
Anyone diagnosed with cancer should have a detailed personal and family cancer history taken. People with a strong family history of colorectal cancer or high-risk familial syndromes should be referred to a familial cancer service for genetic risk assessment and possible genetic screening of affected relatives. Younger patients under 50 years should be referred to a familial cancer service. Consult relevant guidelines to determine if referral to a familial cancer service is appropriate.
Mainstream genetic testing is now available and funded through Medicare for the mismatch repair genes, APC, MUTYH and the hamartomatous polyposis genes. However, a familial cancer service assessment can assist and determine if genetic testing is appropriate. Genetic testing should be offered when there is at least a 10 per cent chance of finding a causative ‘gene error’ (pathogenic gene variant; previously called a mutation). Tumour testing for mismatch repair (MMR) protein expression or microsatellite testing is the main avenue to determining this risk for lynch syndrome. Usually testing begins with a variant search in a person who has had cancer (a diagnostic genetic test). If a pathogenic gene variant is identified, variant-specific testing is available to relatives to see if they have inherited the familial gene variant (predictive genetic testing). Depending on the personal and family history, the relevant state health system may support funding in the public sector for additional germline testing.
Pre-test counselling and informed consent is required before any genetic testing in any setting. A familial cancer service can organise this, as well as provide risk management advice, facilitate family risk notification and arrange predictive cascade genetic testing for the family.
Visit the Centre for Genetics Education website for basic information about cancer in a family.
For detailed information and referral guidelines for colorectal cancer risk assessment and consideration of genetic testing, see these resources:
Pharmacogenetics describes how individual genetic differences can lead to differences in the way certain medicines interact with the body. These interactions can affect the effectiveness of medications and any side effects. Applying pharmacogenetics to treatment planning may help patients to be prescribed the most appropriate treatment at the optimal dose from the beginning of treatment (NHMRC 2013).
