S. Ballantyne, Glasgow, GB

Watch-and-wait (W&W) is an emerging treatment strategy for patients considered to have complete response to neoadjuvant chemoradiotherapy (nCRT) on the basis of post-treatment MRI and endoscopy, potentially avoiding the need for surgery. This audit reviews our initial experience of using MRI in this setting and identifies the rate and patterns of local recurrence.

Material and methods

The local radiology database was used to find patients who had been identified on post-nCRT MRI as possible complete responders between 2013-2019. Reports of their initial post treatment MRI and endoscopy and subsequent W&W MRI and endoscopic exams were reviewed.

Results

30 patients were identified as having a complete response to nCRT on MRI and endoscopy. Median follow-up 2 years (0.7 – 6.3 years) and median number of MRI exams 3 (1-10). 10 patients (33%) developed recurrence: median 1 year (0.5 – 3.3 years). The positive-predictive value (PPV) of MRI in identifying recurrence (T2W +/- DWI) was 63%. The PPV of T2W findings alone was 17%. The PPV of scans with additional DWI findings was 100%. The negative-predictive-value of MRI was 98%.

Conclusion

The rate of local recurrence of rectal cancer in those considered complete responders to nCRT (33%) is similar to recent meta-analyses. MRI had a reasonable PPV for the detection of recurrence and, where present, the addition of DWI to T2W findings significantly increased the PPV. MRI was highly accurate in excluding local recurrence on follow-up.

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