This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Initial investigation which includes whole-body magnetic resonance imaging (MRI) is as good as standard pathways for detecting metastatic disease in adults with newly diagnosed colorectal cancer. This NIHR-funded study also found that whole-body MRI reduces the number of investigations needed, the length of the staging process, and costs less than standard pathways.
The treatment options for colorectal cancer depend on the stage of the cancer. For example, if a patient has metastatic disease (secondary tumours in other parts of the body), the aims of surgery and chemotherapy can be different. So, an accurate staging process is very important.
Current NICE guidance recommends a sequence of investigations for staging, with MRI only recommended after biopsies and other imaging investigations. This study suggests that MRI could be used earlier in the process, instead of the currently recommended investigations. However, any changes to guidance would need to take into account the availability of this resource.
Why was this study needed?
About 42,000 new cases of colorectal cancer are diagnosed each year in the UK. Just over 16,000 people die from the disease annually. Treatment options depend on the stage of the cancer and particularly whether metastases have been identified.
Current staging pathways use a sequence of imaging tests, such as computerised tomography (CT), positron emission tomography/computerised tomography (PET-CT) and MRI. These differ in their ability to detect metastases in different body parts. Whole-body MRI could be an alternative initial investigation to the current complex pathways, but there is a lack of evidence about how effective it could be for colorectal cancer staging.
This study aimed to compare the diagnostic accuracy of whole-body MRI staging pathways with standard pathways. It also investigated any differences in staging times, extra tests, costs and treatment decisions.
What did this study do?
This diagnostic accuracy study included 299 adults with a new diagnosis of colorectal cancer from 16 hospitals in the UK. Participants had whole-body MRI, as well as the other standard staging investigations.
Initial treatment decisions were made using only the usual care investigations. Then the MRI findings were revealed. The clinicians decided which additional tests they would want in order to make a decision, and these were arranged if they had not already been done. Finally, treatment decisions were made based on all the investigations together.
The opinion of an expert multidisciplinary review panel, based on all initial investigations and follow-up data at 12 months were used as the reference - to act as the ‘correct’ or true diagnosis for the comparison.
What did it find?
- The pathways were similar in their ability to correctly identify metastatic disease (sensitivity) in those later proven to have them; this was 67% for whole-body MRI compared with 63% for standard pathways (difference 4%, 95% confidence interval [CI] ‑5% to 13%).
- There was no difference between the pathways in their ability to correctly diagnose the stage of those without metastases (specificity), which was 95% for whole-body MRI versus 93% for standard pathways (difference 2%, 95% CI ‑2% to 6%).
- Decisions made using either pathway were the same as the decisions made by the review panel 96% of the time for whole-body MRI and 95% for the standard pathway.
- The median length of the staging process was shorter for whole-body MRI, 8 days (95% CI 6 to 9 days) compared with 13 days for standard pathways (95% CI 11 to 15 days). Whole-body MRI pathways required just one test on average, including whole-body MRI, compared to two tests for standard pathways.
- Average costs per patient were lower for the whole-body MRI group at £216 (95% CI £211 to £221), compared with £285 for the standard pathway group (95% CI £260 to £310).
What does current guidance say on this issue?
NICE updated its guideline on the diagnosis and management of colorectal cancer in 2014. It does not recommend MRI for initial diagnostic investigations. It recommends contrast-enhanced CT of the chest, abdomen and pelvis to estimate the stage of disease for all patients diagnosed with colorectal cancer.
For patients with colon cancer, the guideline recommends no further routine imaging is needed. For patients with rectal cancer, it recommends MRI to assess the risk of local recurrence.
This guidance is currently being reviewed, with an update expected to be published in January 2020.
What are the implications?
This study suggests that whole-body MRI is accurate if added to the pathway for diagnosis, staging and planning treatment of colorectal cancer. The whole-body MRI pathway gave similar results to current pathways in terms of identifying metastatic disease and resulted in the same treatment decisions. It also reduced the number of tests needed, speeded up the staging process and lowered the costs.
The study reflects how imaging is currently carried out and interpreted in UK hospitals, though half of them were not currently able to offer whole-body MRI themselves, and this had to be done by a nearby hospital.
The findings support a change in practice and may inform future updates to the guidance.
Citation and Funding
Taylor S, Mallett S, Beare S et al. Diagnostic accuracy of whole-body MRI versus standard imaging pathways for metastatic disease in newly diagnosed colorectal cancer: the prospective Streamline C trial. Lancet Gastroenterol Hepatol. 2019;4(7):529-37.
This project was funded by the NIHR Health Technology Assessment Programme (project number 10/68/01).
Bibliography
Cancer Research UK. Bowel cancer statistics. London: Cancer Research UK; accessed June 2019.
NHS website. Bowel cancer. London: Department of Health; 2016.
NICE. Colorectal cancer: diagnosis and management. CG131. London: National Institute for Health and Care Excellence; 2014.
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