Korean J Radiol.  2020 Jul;21(7):812-828. 10.3348/kjr.2020.0483.

MRI Assessment of Complete Response to Preoperative Chemoradiation Therapy for Rectal Cancer: 2020 Guide for Practice from the Korean Society of Abdominal Radiology

Affiliations
  • 1Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea
  • 2Department of Radiology, Kyungpook National University Medical Center, School of Medicine, Kyungpook National University, Daegu, Korea
  • 3Department of Radiology, Ewha Womans University Seoul Hospital, Seoul, Korea
  • 4Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Korea
  • 5Department of Radiology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
  • 6Department of Radiology, Kyung Hee University Hospital, Seoul, Korea
  • 7Department of Radiology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea

Abstract


Objective
To provide an evidence-based guide for the MRI interpretation of complete tumor response after neoadjuvant chemoradiation therapy (CRT) for rectal cancer using visual assessment on T2-weighted imaging (T2) and diffusion-weighted imaging (DWI).
Materials and Methods
PubMed MEDLINE, EMBASE, and Cochrane Library were searched on November 28, 2019 to identify articles on the following issues: 1) sensitivity and specificity of T2 or DWI for diagnosing pathologic complete response (pCR) and the criteria for MRI diagnosis; 2) MRI alone vs. MRI combined with other test(s) in sensitivity and specificity for pCR; and 3) tests to select patients for the watch-and-wait management. Eligible articles were selected according to meticulous criteria and were synthesized.
Results
Of 1615 article candidates, 55 eligible articles (for all three issues combined) were identified. Combined T2 and DWI performed better than T2 alone, with a meta-analytic summary sensitivity of 0.62 (95% confidence interval [CI], 0.43– 0.77; I2 = 80.60) and summary specificity of 0.89 (95% CI, 0.80–0.94; I2 = 92.61) for diagnosing pCR. The criteria for the complete response on T2 in most studies had the commonality of remarkable tumor decrease to the absence of mass-like or nodular intermediate signal, although somewhat varied, as follows: (near) normalization of the wall; regular, thin, hypointense scar in the luminal side with (near) normal-appearance or homogeneous intermediate signal in the underlying wall; and hypointense thickening of the wall. The criteria on DWI were the absence of a hyperintense signal at high b-value (≥ 800 sec/mm2) in most studies. The specific algorithm to combine T2 and DWI was obscure in half of the studies. MRI combined with endoscopy was the most utilized means to select patients for the watch-and-wait management despite a lack of strong evidence to guide and support a multi-test approach.
Conclusion
This systematic review and meta-analysis provide an evidence-based practical guide for MRI assessment of complete tumor response after CRT for rectal cancer.

Keyword

Rectal cancer; Adenocarcinoma; Chemoradiotherapy; Chemoradiation; Response; Remission; Regression; CR; Magnetic resonance imaging; Watch and wait; Wait and see; Organ preservation; Surveillance; Evidence; Guideline; Recommendation
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