Discussion
The acceptability or otherwise of WB-MRI as a replacement for current multi-modality pathways is dependent on many factors, most notably diagnostic accuracy and patient acceptability, the latter governed by the contrasting attributes of alternative staging pathways. Using a DCE, we identified those desirable attributes that most influence patient preferences and identified circumstances in which WB-MRI pathways would be preferred by the majority over current staging pathways.
As would be expected, we found that patients generally prefer to wait less time for staging, reduce the cancer risk due to radiation exposure, and undergo fewer scans with greater accuracy. For patients with lung cancer, time to diagnosis was the attribute valued most highly, followed by accuracy, cancer risk from radiation exposure, number of additional scans, and time in a scanner. For patients with colorectal cancer, accuracy was valued most highly, followed by time to diagnosis, cancer risk from radiation exposure, and number of additional scans. Diagnostic accuracy however had a greater influence on the preferences of lung cancer patients who were home-owning or had higher self-rated health. Differences between the two cohorts could therefore reflect demographic and health differences, with colorectal cancer patients reporting lower deprivation, higher educational level, and better health than lung cancer patients. However, the analyses by sub-group within each cohort were exploratory and further research to explore the observed variations would be beneficial.
The length of time in the scanner was a significant factor affecting preferences for patients with lung cancer only, likely because this group finds prolonged scans more challenging. In support, previous data from patients recruited to the Streamline trials have shown that in general, patients with lung cancer find WB-MRI more demanding, often because they cannot hold their breath easily or lie flat for long periods [
3].
Cancer risk from radiation exposure significantly influenced the preferences of both cohorts, although was deemed less important than test accuracy and time to diagnosis. The long-term prognosis of the recruited cohort is clearly heavily dependent on their age and underlying primary cancer diagnosis rather than the theoretical small additional cancer risk due to staging investigations. It is likely improved patient education would reduce their perceived importance of ionising radiation exposure, but, nonetheless, long-term survivorship is common for both cancers (particularly colorectal) and exposure to radiation is clearly a legitimate patient concern.
Just over a third of participants were ‘non-traders’, with preferences anchored to a single attribute, most commonly diagnostic accuracy. Traders (who formed the majority) were willing to accept inferior levels of one attribute in turn for improvement in another. For example, the marginal rates of substitution suggest that in return for a 5% improvement in accuracy, patients with colorectal cancer would be prepared to wait an additional 2.25 weeks for their final staging diagnosis and undergo an additional 3.5 scans. Similarly, patients with lung cancer are willing to wait 1.45 weeks for their final staging diagnosis or undergo an additional 3.05 scans for the same 5% accuracy improvement. Many patients were also willing to trade for a reduction in cancer risk due to radiation exposure. For example, to avoid a 1/1000 increase in cancer risk from scan-related radiation exposure, lung cancer patients would wait around 1.11 weeks more for their final diagnosis, despite its likely limited impact on overall prognosis.
This trading of attributes is reflected in overall patient preferences for the various pathway scenarios presented. Patients with lung or colorectal cancer were more likely to prefer a WB-MRI pathway compared with default staging as long as it was as accurate and results in the same scan number and time to diagnosis. As noted above, this suggests that a lack of radiation exposure is believed important by patients. If, however, WB-MRI is more accurate than the standard pathway, reduces time to diagnosis, and/or results in fewer scans, then the preference for WB-MRI is even stronger. Indeed, if WB-MRI is more accurate, reduces time to diagnosis, and results in fewer scans, the probability of preferring it over the standard staging pathway is 0.89 in patients with lung cancer and 0.99 in patients CRC.
Likelihood ratio tests rejected the null hypothesis that none of the attributes were related to preferences. This also provides some reassurance that the problem of multiple comparisons did not arise in our analyses.
Our results were very similar between patients with lung and colorectal cancer, and so we envisage the data could potentially be extrapolated to staging other cancers. However, there were some differences between lung and colorectal cancer patients, which may be in part due to underlying differing comorbidities. It is possible, for example, that patients with pain due to bony metastasis (for example in myeloma) may find prolonged WB-MRI protocols more challenging and this should be investigated. Furthermore, research on patient preferences for WB-MRI vs CT in patients undergoing lymphoma staging showed patients found WB-MRI less unpleasant and less worrisome than CT [
20]. The authors attributed their findings to the more invasive preparation required for CT in their scan protocol (patients required intravenous lines and had to consume oral contrast). In our study, WB-MRI protocols required IV gadolinium which may help explain discrepant findings.
The study has limitations. It was powered to detect differences between the two cancer cohorts, but not to detect differences within each cancer type. This may explain non-significant effects across a number of different demographics. The need to enclose the whole body and head did not influence scan preferences when balanced against other test attributes. Previous work has demonstrated that claustrophobia is problematic for many patients undergoing MRI [
5,
21]. Patients recruited to the Streamline trials were, by definition, willing to undergo WB-MRI and may therefore not be representative of an unselected cancer patient cohort, particularly given the general prevalence of claustrophobia. Indeed, the majority of participants had already had the WB-MRI scan prior to completing the study. Of note, however, when given a binary choice, lung cancer patients stating an overall preference for standard staging scans preferred less time in a scanner and not to have their whole body and head enclosed compared with those preferring WB-MRI.
Future research could assess what attributes WB-MRI would need to possess in order to appeal to people who are more reluctant to undergo a full body scan.
In conclusion, patients with cancer are willing to trade staging pathway attributes, for example prolonging time to diagnosis, in return for increased accuracy and/or reduced diagnostic radiation exposure. Staging pathways based on first-line WB-MRI are preferred by most patients if they at least match standard pathways for diagnostic accuracy, time to diagnosis, and total scan number. If WB-MRI staging improves any or all these attributes, patient preference is stronger.
Acknowledgements
Study collaborators
*STREAMLINE investigators
The authors of this paper are part of a wider group that form the Streamline trials investigators and include the following collaborators: A Aboagye, L Agoramoorthy, S Ahmed, A Amadi, G Anand, G Atkin, A Austria, S Ball, F Bazari, R Beable, H Beedham, T Beeston, N Bharwani, G Bhatnagar, A Bhowmik, L Blakeway, D Blunt, P Boavida, D Boisfer, D Breen, S Burke, R Butawan, Y Campbell, E Chang, D Chao, S Chukundah, B Collins, C Collins, V Conteh, J Couture, J Crosbie, H Curtis, A Daniel, L Davis, K Desai, M Duggan, S Ellis, C Elton, A Engledow, C Everitt, S Ferdous, A Frow, M Furneaux, N Gibbons, R Glynne-Jones, A Gogbashian, S Gourtsoyianni, A Green, Laura Green, Liz Green, A Groves, A Guthrie, E Hadley, A Hameeduddin, G Hanid, S Hans, B Hans, A Higginson, L Honeyfield, H Hughes, J Hughes, L Hurl, E Isaac, M Jackson, A Jalloh, R Jannapureddy, A Jayme, A Johnson, E Johnson, P Julka, J Kalasthry, E Karapanagiotou, S Karp, C Kay, J Kellaway, S Khan, D-M Koh, T Light, P Limbu, S Lock, I Locke, T Loke, A Lowe, N Lucas, S Maheswaran, S Mallett, E Marwood, J McGowan, F Mckirdy, T Mills-Baldock, T Moon, V Morgan, S Nasseri, P Nichols, C Norman, E Ntala, A Nunes, A Obichere, J O’Donohue, I Olaleye, A Onajobi, T O’Shaughnessy, A Padhani, H Pardoe, W Partridge, U Patel, K Perry, W Piga, D Prezzi, K Prior, S Punwani, J Pyers, H Rafiee, F Rahman, I Rajanpandian, S Ramesh, S Raouf, K Reczko, A Reinhardt, D Robinson, P Russell, K Sargus, E Scurr, K Shahabuddin, A Sharp, B Shepherd, K Shiu, H Sidhu, I Simcock, C Simeon, A Smith, D Smith, D Snell, J Spence, R Srirajaskanthan, V Stachini, S Stegner, J Stirling, N Strickland, K Tarver, J Teague, M Thaha, M Train, S Tulmuntaha, N Tunariu, K van Ree, A Verjee, C Wanstall, S Weir, S Wijeyekoon, J Wilson, S Wilson, T Win, L Woodrow, D Yu.