Pelvic MRI after induction chemotherapy and before long-course chemoradiation therapy for rectal cancer: What are the imaging findings?
To determine the appearance of rectal cancer on MRI after oxaliplatin-based chemotherapy (ICT) and make a preliminary assessment of MRI’s value in predicting response to total neoadjuvant treatment (TNT).
In this IRB-approved, HIPAA-compliant, retrospective study between 1 January 2010–20 October 2014, pre- and post-ICT tumour T2 volume, relative T2 signal intensity (rT2SI), node size, signal intensity and border characteristics were assessed in 63 patients (65 tumours) by three readers. The strength of association between the reference standard of histopathological percent tumour response and tumour volume change, rT2SI and lymph node characteristics was assessed with Spearman’s correlation coefficient and Wilcoxon’s rank sum test. Cox regression was used to assess association between DFS and radiological measures.
Change in T2 volume was not associated with TNT response. Change in rT2SI showed correlation with TNT response for one reader only using selective regions of interest (ROIs) and borderline correlation with response using total volume ROI. There was a significant negative correlation between baseline and post-ICT node size and TNT response (r = -0.25, p = 0.05; r = -0.35, p = 0.005, readers 1 and 2, respectively). Both baseline and post-induction median node sizes were significantly smaller in complete responders (p = 0.03, 0.001; readers 1 and 2, respectively). Change in largest baseline node size and decrease in post-ICT node signal heterogeneity were associated with 100% tumour response (p = 0.04). Nodal sizes at baseline and post-ICT MRI correlated with DFS.
In patients undergoing post-ICT MRI, tumour volume did not correlate with TNT response, but decreased lymph node sizes were significantly associated with complete response to TNT as well as DFS. Relative T2SI showed borderline correlation with TNT response.
• MRI-based tumour volume after induction chemotherapy and before chemoradiotherapy did not correlate with overall tumour response at the end of all treatment.
• Lymph node size after induction chemotherapy and before chemoradiotherapy was strongly associated with complete pathological response after all treatment.
• Lymph node sizes at baseline and post-induction chemotherapy MRI correlated with disease-free survival.
KeywordsRectal cancer Chemotherapy MRI Total neoadjuvant treatment
Dynamic contrast-enhanced sequences
- FOLFOX 5
Upfront chemotherapy (‘induction’)
Magnetic resonance tumour regression grade
Pathological complete response
Relative T2 signal intensity
Total mesorectal excision
Total neoadjuvant treatment
This study has received funding by the National Cancer Institute of the National Institutes of Health under Award Number R25CA020449. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health
Compliance with Ethical Standards
The scientific guarantor of this publication is Marc J. Gollub
Conflict of Interest
The authors of this article declare no relationships with any companies whose products or services may be related to the subject matter of the article.
Statistics and Biometry
Andrea Knezevic and Mithat Gonen kindly provided statistical advice for this article.
No complex statistical methods were necessary for this paper.
Written informed consent was waived by the Institutional Review Board.
Institutional Review Board approval was obtained.
• Cross-sectional study/observational
• Performed at one institution
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