Korean J Radiol.
2024 Apr;25(4):351-362. 10.3348/kjr.2023.1213.
Interpretation of Complete Tumor Response on MRI Following Chemoradiotherapy of Rectal Cancer: Inter-Reader Agreement and Associated Factors in Multi-Center Clinical Practice
- Affiliations
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- 1Department of Radiology, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
- 2Department of Radiology, Kyungpook National University Chilgok Hospital, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
- 3Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea
- 4Department of Radiology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
- 5Department of Radiology, Hanyang University College of Medicine, Seoul, Republic of Korea
- 6Department of Radiology, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
- 7Department of Radiology, Kyung Hee University Hospital, Seoul, Republic of Korea
- KMID: 2554289
- DOI: http://doi.org/10.3348/kjr.2023.1213
Abstract
Objective
To measure inter-reader agreement and identify associated factors in interpreting complete response (CR) on magnetic resonance imaging (MRI) following chemoradiotherapy (CRT) for rectal cancer.
Materials and Methods
This retrospective study involved 10 readers from seven hospitals with experience of 80–10210 cases, and 149 patients who underwent surgery after CRT for rectal cancer. Using MRI-based tumor regression grading (mrTRG) and methods employed in daily practice, the readers independently assessed mrTRG, CR on T2-weighted images (T2WI) denoted as mrCR T2W, and CR on all images including diffusion-weighted images (DWI) denoted as mrCRoverall. The readers described their interpretation patterns and how they utilized DWI. Inter-reader agreement was measured using multi-rater kappa, and associated factors were analyzed using multivariable regression. Correlation between sensitivity and specificity of each reader was analyzed using Spearman coefficient.
Results
The mrCR T2W and mrCRoverall rates varied widely among the readers, ranging 18.8%–40.3% and 18.1%–34.9%, respectively. Nine readers used DWI as a supplement sequence, which modified interpretations on T2WI in 2.7% of cases (36/1341 [149 patients x 9 readers]) and mostly (33/36) changed mrCR T2W to non-mrCRoverall. The kappa values for mrTRG, mrCR T2W, and mrCRoverall were 0.56 (95% confidence interval: 0.49, 0.62), 0.55 (0.52, 0.57), and 0.54 (0.51, 0.57), respectively. No use of rectal gel, larger initial tumor size, and higher initial cT stage exhibited significant association with a higher interreader agreement for assessing mrCRoverall (P ≤ 0.042). Strong negative correlations were observed between the sensitivity and specificity of individual readers (coefficient, -0.718 to -0.963; P ≤ 0.019).
Conclusion
Inter-reader agreement was moderate for assessing CR on post-CRT MRI. Readers’ varying standards on MRI interpretation (i.e., threshold effect), along with the use of rectal gel, initial tumor size, and initial cT stage, were significant factors associated with inter-reader agreement.
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