30 HOW TO TREAT: COLORECTAL CANCER: DIAGNOSIS
30 HOW TO TREAT: COLORECTAL CANCER: DIAGNOSIS
11 APRIL 2025 ausdoc. com. au
Ed Uthman / CC BY 2.0 / bit. ly / 46OSdw2
Figure 4. Large colon cancer arising in an adenoma. The patient, a middleaged woman, presented with colon perforation and paracolonic abscess. Diagnosis was made at laparotomy.
PAGE 27 with involved margins may mandate segmental colorectal resection( see figures 4 and 5).
Other screening methods
CT COLONOGRAPHY CT colonography( see figure 6) is of use where colonoscopy is contraindicated. However, CT colonoscopy still requires bowel preparation, which is often the main point of clinical concern in the elderly, infirm patient. In addition, there is still a small risk of perforation and complications.
A patient with a positive CT colonography will still need colonoscopic confirmation, meaning its role is limited. It may, however, be of value in patients in whom complete colonoscopy with caecal intubation cannot be accomplished.
For a patient to receive a Medicare rebate( item number 56553), one of the following must apply: incomplete colonoscopy within three months, high-grade colonic obstruction, or the request must come from a surgeon or consultant physician who practises colonoscopy.
STOOL DNA STUDIES AND BLOOD MARKERS None of these studies are currently Medicare rebatable. Stool DNA studies do not appear to have much clinical benefit over FOBT, are expensive, and appear to have a high false positive rate.
While there is considerable excitement about blood cancer screening tests, these are not currently approved in Australia, and research into these is still in its infancy.
Box 4. General guidelines to reduce risk of colorectal cancer
• There is evidence for reducing risk of CRC by:— Maintaining a normal weight( BMI 20-25kg / m 2).— Eating five or more portions per day of a variety of vegetables and fruit all year round.— Consuming poorly soluble fibres.— Reducing consumption of lean red meats( no more than 100g a day).— Avoiding processed and charred meats.— Avoiding smoking.— Participating in regular physical activity( the greatest benefit is seen with 10 hours of average paced walking a week).— Limiting alcohol to no more than two standard drinks a day for men and one standard drink a day for women.— Increasing calcium and vitamin D intake.
• Chemoprevention:— Consider 100mg aspirin a day in all patients aged between 45 and 70 years for chemoprevention for colorectal cancer.
• The duration should be for at least 2.5 years, and benefits do not arise earlier than 10 years after initiation of the medication.
— Conduct screening for H. pylori because the GI toxicity of aspirin is enhanced by the presence of H. pylori.— Carefully consider the individual benefits and risks, including the cardiovascular benefits versus the risks of bleeding, gastric ulcers and renal impairment.
INHERITED BOWEL CANCER Most patients who develop CRC in the setting of a positive family history do so through an ill-defined, heterogeneous mix of genes. There are, however, some specific syndromes for which testing is available. Outcomes may have a profound impact on further testing and advice for patients and their families. While detailed discussion of these is outside the scope of this article, be aware that these patients require much more intensive screening; consider referral to a familial cancer clinic for any patient with a family predisposition of the conditions listed in box 5.
While there is considerable excitement about blood cancer screening tests, these are not approved in Australia, and research into these is still in its infancy.
COLONOSCOPY While colonoscopy is the gold standard for diagnosis of colorectal cancer( see figures 7 and 8), it has additional value in its ability to prevent colorectal cancer through the treatment of pre-cancerous polyps.
Small polyps( up to 1cm) can either be removed by a snare( lasso-like device), or a biopsy forceps, usually without electrocautery.
Larger polyps( 1-2cm) can be removed using a snare with electrocautery to reduce the risk of bleeding.
The use of advanced colonoscopic techniques, such as endoscopic mucosal resection or endoscopic submucosal dissection, with the use of tools such as submucosal injection and electric knife, allow for the resection of even larger polyps.
These techniques, which require specialised training, do increase the risk of perforation and bleeding. Mechanical clips can be placed to reduce this risk.
Box 5. Genetic syndromes involving CRC
• Hereditary non-polyposis colorectal cancer / Lynch syndrome:— Endometrial.— Gastric.— Ovarian.— Small bowel.— Pancreatic.— Urinary tract.— Smaller increased risks of prostate and breast.
• Familial polyposis syndrome:— Desmoid tumours.— Gastric / duodenal.— Hepatoblastoma.— Thyroid.— Skull osteomas.— Endometrial.
Many patients may be referred for open-access colonoscopy, where the proceduralist may not meet the patient until the day of the procedure.
With the changes in the Medicare rules, it is vital a clear indication is stated on the referral. As always, the patient should be fit, without significant cardiorespiratory disease or diabetes.
Although it is still contentious, there is evidence that small polyps may be removed without stopping anticoagulation or antiplatelet agents. 10
Patients taking these medications typically remain unsuitable for open-access colonoscopy, and decisions regarding the continuation or temporary cessation of these