The problem
Liver metastases are followed by repeated CT scans, and how lesions change between scans informs every treatment review. That assessment is made by hand, varies between readers, and falls on a workforce that is already short.
Many patients, many scans.
Bowel cancer is the fourth most common cancer in the UK, and the liver is where it most often spreads.
developed liver metastases within five years, in a population study of 1,026 patients
Engstrand et al., BMC Cancer 2018 (Stockholm)people a year in the UK, if that rate applies here. Each is scanned every 2 to 3 months during treatment.
Our estimate from the two figures before itTwo readers, two answers.
Under the RECIST 1.1 rules, response is judged from the sum of the target lesions' diameters: a rise of at least 20% (and at least 5 mm) counts as progression, and a fall of at least 30% as partial response.
When two radiologists measure the change in the same single lesion, their answers can differ by up to about 30% either way (95% limits of agreement). Differences of that size can be enough to move an assessment across one of those lines.
Show the numbers as a table
| Situation | Lower limit | Upper limit |
|---|---|---|
| One reader, measuring one lesion twice | -17.8% | +16.1% |
| Two readers, measuring the same lesion | -22.1% | +25.4% |
| Two readers, measuring change between scans | -31.3% | +30.3% |
Show the numbers as a table
| Year | Shortfall |
|---|---|
| 2024 | 29% |
| 2025 | 32% (over 2,300 radiologists) |
| 2030, forecast if no action | 40% (over 4,050) |
Fewer people to read more scans.
The UK has 32% fewer radiologists than it needs, and without action the gap is forecast to reach 40% by 2030.
Every follow-up read that has to be done from scratch, finding and re-measuring each lesion by hand, competes for the same reporting time.
What a follow-up read asks of a radiologist.
The steps are simple to list. Done by hand, each one takes time and invites disagreement.
Find every lesion again
On a new scan with a different slice position, breathing and contrast timing.
Decide which is which
Match each lesion to the same one on the earlier scan, including ones that are new or gone.
Measure each one
Choose the slice and the axis, then measure, the same way as last time.
Work out the change
For each lesion and for the total, and decide what it means for treatment.
Work with us
We are looking for hospitals and research groups with baseline and follow-up CT of colorectal liver metastases, radiologists for a reader study, and academic and NHS partners for funded validation.
Please do not email patient images or patient information.