Colorectal Cancer
- Most bowel cancers are diagnosed in symptomatic patients
- 2nd most common cause of cancer death
- Australia has one of the highest rates of colorectal cancer globally.
- Colorectal cancer was the third most commonly diagnosed cancer in Australia in 2018.
- In 2022, an estimated 15,713 Australians were diagnosed with colorectal cancer, and 5,326 died from it.
- Screening with the immunochemical faecal occult blood test (iFOBT) is highly cost-effective.
Risk Factors
Family History (non-syndrome related)
- Higher risk Family History Criteria (RR 3-4x)
- One first degree relative with Colorectal Cancer or advanced adenoma before age 60 years
- Two first degree relatives with Colorectal Cancer or advanced adenoma at any age
- Moderate risk Family History Criteria (RR 2-3x)
- One first degree relative with Colorectal Cancer or advanced adenoma age 60 years or older
- Two second degree relatives with Colorectal Cancer or advanced adenoma at any age
Hereditary Syndromes
- Familial Adenomatous Polyposis (>100 synchronous advanced adenomas)
- Diagnosed on average by age 39 years, and 87% develop Colon Cancer by age 45 years old
- Hereditary non-polyposis Colon Cancer (Lynch Syndrome)
- Diagnosed on average by age 45 years, and 75-80% lifetime Colon Cancer risk
- Autosomal dominant condition caused by germline mutations
- Most common cause of inherited Colorectal Cancer
- Surveillance colonoscopy every 1 to 2 years is recommended for individuals carrying a germline mutation
- Peutz-Jeghers Syndrome (Hamartomatous Polyposis)
- Symptomatic polyps by age 10 to 30 years
- Sessile Serrated Adenomatous Polyposis
- Diagnosed on average by age 62 years, and 25-70% have Colon Cancer at time of diagnosis
Lifestyle related risks
- Tobacco Abuse
- Current smokers have a 2 fold higher Relative Risk of high-risk adenomas or Colorectal Cancer
- Obesity
- BMI 35-40 associated with Colorectal Cancer mortality Relative Risk 1.8 in men, 1.4 in women
- Bariatric Surgery reduced Colorectal Cancer rtisk by 27%
- Dietary Risk Factors
- Dairy products have a minimal impact on Colorectal Cancer risk
- Red Meat
- Foods with possible higher risk: Salt-cured, pickled, smoked, barbeque
- Red meat consumption does increase Colorectal Cancer risk
Spread
- Lymphatics – epigastric and para-aortic nodes
- Direct- peritoneum
- Blood – portal ciruclation
- Symptoms may depend on location
- Right – anaemia, dyspepsia, mass
- Left – pain, obstruction, altered bowel habit
- Sigmoid – obstruction, altered bowel habit, rctal bleeding
- Distal bowel/rectal – mass, rectal bleeding, tenesmus
History
- Often common , non specific symptoms with many causes- be suspicious if there is a combination of > 1 symptom or aged > 50
- Altered bowel habit
- Frequency, consistency, calibre(narrowing)
- Often increased frequency/loose stools if left sided
- If change in bowel habit persists > 6 weeks – consider suspicious for malignancy/other pathology
- Rectal bleeding
- More commonly intermixed
- Abdominal pain
- Anal pain and tenesmus
- Constitutional symptoms – weight loss, night sweats, fevers
- Symptoms of anaemia
- Fatigue, dizziness, SOB, exercise intolerance, palpitations, apthous ulcers, angular chelitis, restless legs
- Explore family history
- Any other GI disorders
Examination
- Vitals, height, weight, BMI
- Signs of anaemia – pallor, tachycardia, heart murmur
- Palpate abdo – focal tenderness, masses, organomegaly
- Regional lymphadenopathy
- Perianal region – haemorrhoids or fissures to differentiate
- DRE – exclude rectal mass
Investigations
- Baseline bloods, inc iron studies
- If iron deficient – needs scopes
- If abdominal pain/mass – consider CT
- If there are red flags or > 1 colorectal symptom – refer for surgery or gastro assessment
- If identify benign pathology (e.g. Hemorrhoids) – manage accordingly and review at 6-8 weeks. If persistent or worsening symptoms refer
- CEA is not useful for diagnosis – may be for monitoring response to treatment
Management
- Early surgical excision
- Chemotherapy depending on prognosis
- Follow up generally includes
- CEA antigen
- Colonscopy
- Abdominal imaing
- Avoid risks
- Smoking
- Low EtOH
- Healthy BMI
- Aspirin 100mg for 2.5 years between 50 – 50 years
- Diet low in processed/red meat
- High fibre
Bowel Cancer Screening
| iFOBT / FIT Sensitivity for CRC | iFOBT / FIT Specificity for CRC | Key Features & Comments |
|---|---|---|
| ▸ 79–88% for CRC (range 53–100%) ▸ 33–40% for advanced adenomas | ≈ 89–95% (threshold dependent ~93% at 20 µg Hb/g stool) | • Detects human globin via antibody • No dietary/drug restrictions • Higher uptake, preferred by NBCSP • detects ~8–9 CRCs per 1,000 colonoscopies. |
Screening Modality of Choice
| Modality | Average-risk (Category 1) role | Key advantages | Key caveats |
|---|---|---|---|
| iFOBT / FIT | Primary test, 2-yearly from 45 to 74 y | • Detects human globin → no diet/drug restrictions • Home kit; high uptake | Sensitivity varies with Hb cut-off (15–20 µg Hb/g in NBCSP) |
| Colonoscopy | Not recommended for routine average-risk screening | Direct visualisation ± polypectomy | Invasive; harms (perforation, bleeding) & cost |
Factors Influencing Test Performance
| Factor | Effect on Sensitivity/Specificity |
|---|---|
| Number of samples | 2-sample FIT → ↑ sensitivity by ~7–10%, slight ↓ in specificity |
| Faecal Hb cut-off | ↓ cut-off (e.g., 10 µg/g) → ↑ sensitivity (8–12%), ↓ specificity (6–10%) |
| Stage of CRC | Early-stage: ~85% sensitivity Large/right-sided/advanced lesions → lower bleeding → ↓ sensitivity (~40%) |
| Sample handling | FIT must be returned <14 days & <25°C – degradation → ↓ sensitivity |
| Patient factors | Not for iron-deficiency anaemia or overt bleeding – go straight to colonoscopy (GESA Choosing Wisely) |
How the NBCSP Works (National Bowel Cancer Screening Program 2024 )
| Age group | Access pathway | Cost | Interval |
|---|---|---|---|
| 50–74 y | Automatic mailed kit every 2 y | Free | 2 years |
| 45–49 y | Self-request via National Cancer Screening Register (web form or 1800 627 701) | Free | 2 years |
Risk-Stratified Recommendations
| NHMRC category | Who fits? (simplified) | Test & start age | Frequency | Stop age |
|---|---|---|---|---|
| Category 1 (average) | No ≥1 st-degree relative (FDR) < 60 y with CRC | iFOBT age 45 | 2-yearly | 74 y |
| Category 2 (moderate) | 1 FDR < 60 y or ≥2 relatives (≥1 FDR) any age | Colonoscopy age 50 or 10 y earlier than youngest FDR (whichever earlier) | 5-yearly | 74 y |
| Category 3 (high) | ≥2 FDRs (± SDRs) with CRC, one < 50 y, or Lynch-like family | Colonoscopy age 40 or 10 y earlier than youngest FDR | 5-yearly | 74 y |
Additional measures
- Offer daily low-dose aspirin 45–70 y in Categories 2–3 (conditional).
- Refer Category 3 families for genetics assessment/Lynch syndrome work-up.
Implementation & Pitfalls
| Issue | Practical point |
|---|---|
| Colonoscopy overuse | Despite guidelines, colonoscopy is commonly used for Category 1 patients in high-SES areas → discuss harms & reinforce iFOBT first-line. |
| Recall systems | Positive iFOBT = Category 1 result → must be tracked, communicated, and escalated if colonoscopy wait > 120 days. |
| Patient messaging | “Positive iFOBT ≠ cancer; ~7 in 10 colonoscopies are normal or find benign polyps.” |
| Alternative access model | GPs can provide NBCSP kits directly to under-screened patients via the Register. |
Key Pearls
- Start age: 45 y (guideline) vs 50 y (automatic kit); know the self-request pathway.
- Interval: 2-yearly iFOBT, 5-yearly colonoscopy for Categories 2–3.
- Risk definitions: one FDR < 60 y → Category 2; ≥2 FDRs → Category 3.
- Low-value care: Colonoscopy for average risk is low-value; cite high-SES overuse data.
- Family-history rule of thumb: “10 years younger than the youngest affected FDR” determines colonoscopy start age.
Medico-Legal Landscape (Australia)
| Theme | Example Cases / Sources | Practical Implications for GPs |
|---|---|---|
| Failure to follow up | Bird S., AFP 2006; Ralph v SA (1986) | Must act on every positive FIT – document contact attempts |
| Failure to offer screening | QLS Proctor (2024) case on cervical screening | Offer biennial FIT (50–74 y); from 45 y on request – document refusal |
| Delay in CRC diagnosis | MDO case reports (e.g. missed colonoscopy) | Positive FIT = Category 1 result → recall system required |
| Confidentiality vs consent | PD v Harvey [2003] NSWSC 487 | For mailed NBCSP kits: get consent before discussing with others |
Risk-Management Checklist for GPs
- Embed recalls – electronic follow-up for every pathology request
- Explain clearly – positive FIT ≠ cancer, but mandates colonoscopy
- Escalate delays – document calls to public/private endoscopy providers
- Record consent/refusal – especially if patient declines colonoscopy
- Audit practice – check for missed results, cancer intervals
Consider aspirin for prevention
(fromhttps://app.magicapp.org/#/guideline/j1Q1Xj)
Who to Consider Aspirin For
- Age group:
▸ Recommended: 50–70 years
▸ Consider: 45–74 years, based on individual risk - Risk level:
▸ Average or slightly increased CRC risk (e.g., positive family history without high-risk genetic syndromes) - Life expectancy:
▸ ≥ 10 years, due to delayed onset of benefits
Dosage & Duration
- Dose:
▸ 100–300 mg daily - Duration:
▸ At least 2.5 years, ideally 10 years or more for cancer prevention benefits - Formulation preference:
▸ Use enteric-coated low-dose aspirin to reduce GI side effects
Benefits of Aspirin in CRC Prevention
- Reduction in CRC incidence:
▸ ~ 24% reduction in colorectal cancer risk - Mechanism:
▸ Anti-inflammatory and COX-2 inhibition reduce adenoma progression - Evidence base:
▸ Supported by observational studies and RCTs
▸ Comparable preventive effect to colonoscopy in some populations <70 years
Latency of Chemoprevention
- Time to effect:
▸ ≥ 10 years of continuous use needed for meaningful CRC risk reduction - Implication:
▸ Not suitable for patients with short life expectancy
Personalisation Factors
- Consider age, sex, and overall cardiovascular risk profile
- Dual benefit in some individuals:
▸ Reduces colorectal cancer, MI, ischaemic stroke
Risks and Contraindications
- Common risks:
▸ Dyspepsia, peptic ulcers, GI bleeding, renal impairment - Contraindications:
▸ Active dyspepsia
▸ History of PUD or GI bleeding
▸ Bleeding disorders
▸ Concurrent anticoagulants/antiplatelets
▸ Aspirin allergy
Considerations in Older Women
- Women >65 years:
▸ CRC benefit less clear
▸ May still benefit overall if CVD risk is elevated
▸ Weigh CRC benefit vs GI bleeding risk carefully
When to Refer to Genetics (Lynch Syndrome Risk)
Refer to Familial Cancer Centre / Clinical Genetics Service if:
Personal history of CRC:
- CRC diagnosed <50 years
- CRC + another Lynch-associated cancer
- CRC + family history of 1+ FDR/SDR with CRC or endometrial cancer <50 y
- CRC + 2+ relatives with Lynch-associated cancers (any age)
Family history alone:
- ≥ 2 relatives (FDR or SDR) with CRC or endometrial cancer, 1 diagnosed <50 y
- ≥ 3 relatives with Lynch-associated cancers (any age)
Lynch Syndrome–Associated Cancers Include:
- Colorectal adenocarcinoma
- Endometrial, ovarian, gastric, pancreatic
- Small intestine, cholangiocarcinoma, brain tumour
- Transitional cell carcinoma (ureter/renal pelvis)
- Sebaceous gland tumours, keratoacanthoma
Tips
- Aspirin use for CRC prevention is evidence-based but delayed-onset—don’t recommend in frail or elderly without ≥10-year outlook.
- For moderate family risk, aspirin may be offered as adjunct to surveillance.
- Know red flags for genetic referral—especially multiple Lynch cancers or early-onset cases.
- Counsel carefully: benefits must outweigh GI bleeding risks.
from – Clinical practice guidelines for the prevention, early detection, and management of colorectal cancer: Population screening- Cancer Council Australia, 1.1 published on 22.11.2023 – https://app.magicapp.org/#/guideline/j1Q1Xj
| Adults without symptoms | |||
| Risk level | Average | ||
| Definition | People with no symptoms (age 45–74 years) | ||
| According to family history | |||
| Risk level | Category 1: Average or slightly increased (age 45–74 years) (relative risk x 1–2) | Category 2: Moderately increased (relative risk x 3–6) | Category 3: Individuals at potentially higher risk, where Lynch syndrome has been excluded (relative risk x 7–10) |
| Definition | An individual should be advised that their risk of developing colorectal cancer is: — near-average risk if no family history of colorectal cancer — above average, but less than twice the average risk, if they have only ONE first-degree relative with colorectal cancer diagnosed at age ≥60 years. This level of risk is still not high enough to justify colorectal cancer screening by colonoscopy. | An individual should be advised that their risk of developing colorectal cancer is at least two times higher than average,but could be up to four times higher than average, if they have any of the following: — only 1 first-degree relative with colorectal cancer diagnosed before age 60 years — 1 first-degree relative and one or more second-degree relatives with colorectal cancer diagnosed at any age — 2 first-degree relatives with colorectal cancer diagnosed at any age. Include both sides of the family when assessing an individual’s risk category for colorectal cancer. Criteria for category 2 and category 3 can be met by inclusion of relatives from both sides of the family. | An individual should be advised that their risk of developing colorectal cancer is at least four times higher than average, but could be up to 20 times higher than average, if they have any of the following: — 2 first-degree relatives and one second-degree relative with colorectal cancer, with at least one diagnosed before age 50 years — 2 first-degree relatives and two or more second-degree relatives with colorectal cancer diagnosed at any age — 3 or more first-degree relatives with colorectal cancer diagnosed at any age. Include both sides of the family when assessing an individual’s risk category for colorectal cancer. Criteria for category 2 and category 3 can be met by inclusion of relatives from both sides of the family. |
| Relative risk | At least two times higher than average, but could be up to four times higher than average. | At least four times higher than average, but could be up to 20 times higher than average. | |
| Percentage of Australian population | 98 | 1-2 | <1 |
| Lifetime risk to age 75 years (assuming no colorectal cancer screening) | Approximately 5–10% | Approximately 15–30% | Approximately 30–40% |
| Investigations: | iFOBT screening should be performed in line with population screening every two years from age 45 to age 74. low-dose (100 mg) aspirin daily should be considered from age 45 to 70 in consultation with a health care professional Colonoscopy is generally not recommended for average or slightly increased risk individuals based on family history. Despite this, colonoscopy use is common in high socioeconomic areas. Colonoscopy carries direct and indirect harms, including: – Risk of death, occurring in approximately 1 in 10,000 to 14,000 procedures. – Harms from bowel preparation, such as dehydration and electrolyte imbalances. – Risks from sedation, including cardiovascular events. – Procedure-related risks, such as colonic perforation and bleeding. | colonoscopy should be offered every five years starting at 10 years younger than the earliest age of diagnosis of colorectal cancer in a first-degree relative or age 50, whichever is earlier, to age 74. CT colonography may be offered if clinically indicated. low-dose (100 mg) aspirin daily should be considered from age 45 to 70 in consultation with a health care professional. genetic testing is not indicated at present. | colonoscopy should be offered every five years starting at 10 years younger than the earliest age of diagnosis of colorectal cancer in a first-degree relative or age 40, whichever is earlier, to age 74. ·CT colonography may be offered if clinically indicated. low-dose (100 mg) aspirin daily should be considered from age 45 to 70 (see Aspirin) in consultation with a health professional. referral to a culturally safe family cancer clinic should be considered. Those carrying their family-specific mutation or having uncertain genetic status require careful cancer screening |