Colon cancer screening: Getting the follow-up right

By Dr Natalie Sharpe, Medical Oncologist MBBS, DM

As we come out of Colorectal Cancer Awareness Month, I’m hoping many people took the opportunity to move forward with screening — whether that was booking or completing a colonoscopy.

That’s always a win.

But something that comes up more often than it should is what happens after the colonoscopy. Recently, a patient shared that after a previous colonoscopy, she had been reassured that after a few years she was “back to average risk.” Over a decade later, she presented with colon cancer.

The issue wasn’t that she didn’t get screened — it’s that the follow-up advice wasn’t quite right.

This is a quick, practical refresher on how to approach colon cancer screening and, just as importantly, surveillance.

1. Screening vs surveillance — small distinction, big impact

Screening applies to asymptomatic, average-risk patients.

Surveillance applies to anyone who has had:

• polyps
• colorectal cancer
• or other high-risk findings

Once a patient has had polyps, they are no longer in a standard screening pathway — they are in a surveillance pathway. That shift is where a lot of confusion can happen.

2. Average-risk screening — keeping it simple

For average-risk adults:

• Start screening at age 45
• Continue to age 75 (routine)
• Age 76–85: individualised

If colonoscopy is used:

• A normal colonoscopy → repeat in 10 years

A normal result is reassuring, but it’s not a lifetime clearance — it’s a 10-year interval.

3. Where things often go wrong — after polyps are found

This is the most common area where advice can drift off course.

If polyps are found, follow-up depends on what was removed:

• 1–2 small adenomas (<10 mm): repeat in 7–10 years
• 3–4 adenomas: repeat in 3–5 years
• ≥5 adenomas or any ≥10 mm / high-risk features: repeat in 3 years

So the key idea is:
The findings determine the interval — not just time passing.

Patients aren’t typically “reset” to average risk after a few years simply because nothing new has happened.

4. What’s worth double-checking after a colonoscopy

A quick review of the report can prevent a lot of downstream issues. Ideally, we should know:

• Was the procedure complete and high quality?
• How many polyps were found?
• What were their size and histology?
• What interval was recommended?

If any of that is unclear, it’s worth clarifying rather than making assumptions.

5. Common real-world pitfalls

A few patterns that come up repeatedly:

• Applying 10-year intervals to patients who’ve had polyps
• Assuming “low-risk” means “no follow-up needed”
• Not checking pathology details
• Over-reassuring after a single test
• Patients quietly dropping out of follow-up over time

None of this is intentional — but it’s easy for small gaps to add up.

6. Why this matters

A common scenario looks like this:

• Colonoscopy done
• Polyps removed
• Follow-up not clearly communicated or tracked
• Patient reassured but not recalled
• Many years later → new diagnosis

This is less about one decision and more about how the system holds the patient over time.

7. Practical takeaways

If you want a simple framework:

• Start screening at 45
• Normal colonoscopy → 10-year interval
• Any polyp → think surveillance, not screening
• Check the pathology and recommended interval
• Avoid assuming someone is “back to average risk” without clear justification

Final thought

Colorectal cancer is one of the most preventable cancers we deal with — but only if both the screening and the follow-up are done well.

The colonoscopy is just one step. What we do afterwards matters just as much.