KEY POINTS
- This prospective study evaluated quantitative T1 relaxation mapping in 44 patients with rectal cancer before and six weeks after neoadjuvant treatment.
- Complete response was defined by surgical pathology or, in watch-and-wait patients, magnetic resonance imaging with diffusion-weighted imaging plus endoscopy.
- 18 patients were classified as complete responders and 26 as incomplete responders.
- Post-treatment T1 relaxation time distinguished complete from incomplete response with an area under the receiver operating characteristic curve of 0.94.
- T1 relaxation time was not meaningfully correlated with tumour volume or apparent diffusion coefficient, suggesting that it captured different tissue characteristics.
CLINICAL TAKEAWAY
T1 mapping could complement conventional magnetic resonance imaging and endoscopy when selecting patients for organ preservation. The result is promising but not ready for decision-making: the cohort was small, treatment regimens were heterogeneous and the threshold was developed and evaluated within the same centre.