Diagnostic accuracy of whole-body MRI versus standard imaging pathways for metastatic disease in newly diagnosed colorectal cancer: the prospective Streamline C trial

Background: Whole-body magnetic resonance imaging(WB-MRI) may be an alternative to multi-modality staging of colon cancer but its relative diagnostic accuracy, effect on staging times, test number, cost, and impact on treatment decisions are unknown. We undertook a prospective multicentre cohort study to address this (ISRCTN43958015). Methods: We recruited from 16 English hospitals. Eligible patients were 18 years or older, with newly diagnosed colon cancer. Patients underwent WB-MRI, the result of which was withheld until standard staging investigations were complete. The multi-disciplinary team (MDT) recorded its first treatment decision based on standard investigations, then the alternate WB-MRI staging pathway (WB-MRI plus any additional tests generated), and finally on all tests combined. The primary outcome was difference in per-patient sensitivity for metastases between standard and WB-MRI staging pathways against a consensus reference standard at 12-months. Differences in treatment decisions, staging time, test number, and costs were secondary outcomes. Findings: 299 patients completed the trial; 68 (23%) had metastasis at baseline. The WB-MRI pathway was 68% (95% CI 56 to 78) sensitive, not significantly different from standard pathways (63% [51 to 74]), a 4% (-5 to 13) difference, p=0.508. Specificity was not significantly different (95% [92 to 97], vs. 94% [90 to 96]). Agreement with the MDT final treatment decision was 96% and 95% for WB-MRI and standard pathways respectively. Time to complete staging was significantly shorter for WB-MRI (8 days [6 to 9] vs. 13 days [11 to 15]), a 5-day (3 to 7) difference. WB-MRI pathways required significantly fewer tests (median 1 [1 to 1] vs. 2 [2 to 2]), a difference of 1 (1 to 1). Mean per-patient staging costs were £216 and £285 for WB-MRI and standard pathways respectively. Interpretation: WB-MRI staging pathways are as accurate as standard pathways, but reduce tests, staging time, and cost