Comparison between MRI and pathology in the assessment of tumour regression grade in rectal cancer

Francesco Sclafani, Gina Brown, David Cunningham, Andrew Wotherspoon, Larissa Sena Teixeira Mendes, Svetlana Balyasnikova, Jessica Evans, Clare Peckitt, Ruwaida Begum, Diana Tait, Josep Tabernero, Bengt Glimelius, Susana Roselló, Janet Thomas, Jacqui Oates, Ian Chau

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© The Author(s) named above. Background:Limited data exist regarding the correlation between MRI tumour regression grade (mrTRG) and pathological TRG (pTRG) in rectal cancer.Methods:mrTRG and pTRG were compared in rectal cancer patients from two phase II trials (EXPERT and EXPERT-C). The agreement between radiologist and pathologist was assessed with the weighted κ test while the Kaplan-Meier method was used to estimate survival outcomes.Results:One hundred ninety-one patients were included. Median time from completion of neoadjuvant treatment to pre-operative MRI and surgery was 4.1 weeks (interquartile range (IQR): 3.7-4.7) and 6.6 weeks (IQR: 5.9-7.6), respectively. Fair agreement was found between mrTRG and pTRG when regression was classified according to standard five-tier systems (κ =0.24) or modified three-tier systems (κ =0.25). Sensitivity and specificity of mrTRG 1-2 (complete/good radiological regression) for the prediction of pathological complete response was 74.4% (95% CI: 58.8-86.5) and 62.8% (95% CI: 54.5-70.6), respectively. Survival outcomes of patients with intermediate pathological regression (pTRG 2) were numerically better if complete/good regression was also observed on imaging (mrTRG 1-2) compared to poor regression (mrTRG 3-5) (5-year recurrence-free survival 76.9% vs 65.9%, P=0.18; 5-year overall survival 80.6% vs 68.8%, P=0.22).Conclusions:The agreement between mrTRG and pTRG is low and mrTRG cannot be used as a surrogate of pTRG. Further studies are warranted to assess the ability of mrTRG to identify pathological complete responders for the adoption of non-operative management strategies and to provide complementary prognostic information to pTRG for better risk-stratification after surgery.
Original languageEnglish
Pages (from-to)1478-1485
JournalBritish Journal of Cancer
Issue number10
Publication statusPublished - 7 Nov 2017


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