Modest agreement between magnetic resonance and pathological tumor regression after neoadjuvant therapy for rectal cancer in the real world

Abstract

Magnetic resonance imaging (MRI) is routinely used for preoperative tumor staging and to assess response to therapy in rectal cancer patients. The aim of our study was to evaluate the accuracy of MRI based restaging after neoadjuvant chemoradiotherapy (CRT) in predicting pathologic response. This multicenter cohort study included adult patients with histologically confirmed locally advanced rectal adenocarcinoma treated with neoadjuvant CRT followed by curative intent elective surgery between January 2014 and December 2019 at four academic high‐volume institutions. Magnetic resonance tumor regression grade (mrTRG) and pathologic tumor regression grade (pTRG) were reviewed and compared for all the patients. The agreement between radiologist and pathologist was assessed with the weighted k test. Risk factors for poor agreement were investigated using logistic regression. A total of 309 patients were included. Modest agreement was found between mrTRG and pTRG when regression was classified according to standard five‐tier systems (k = 0.386). When only two categories were considered for each regression system, (pTRG 0‐3 vs pTRG 4; mrTRG 2‐5 vs mrTRG 1) an accuracy of 78% (95% confidence interval [CI] 0.73‐0.83) was found between radiologic and pathologic assessment with a k value of 0.185. The logistic regression model revealed that “T3 greater than 5 mm extent” was the only variable significantly impacting on disagreement (OR 0.33, 95% CI 0.15‐0.68, P = .0034). Modest agreement exists between mrTRG and pTRG. The chances of appropriate assessment of the regression grade after neoadjuvant CRT appear to be higher in case of a T3 tumor with at least 5 mm extension in the mesorectal fat at the pretreatment MRI.

A multiple-time-scale comparative study for the added value of magnetic resonance imaging-based radiomics in predicting pathological complete response after neoadjuvant chemoradiotherapy in locally advanced rectal cancer

“…Posttreatment MTL has been recognized as an effective morphological predictor in assessing pCR as former studies reported ( 24 , 27 , 28 ). Another promising predictor was mrTRG, which reflected the tumor signal status after treatment and highly correlated with the tumor response ( 10 , 29 ). In the comparison of the posttreatment radiomic models (including both the pure radiomic signature and clinical-radiomics model) with the clinical model, there was still no added significant value that emerged, which was the same as the combined models.…”

Advances in MRI-Based Assessment of Rectal Cancer Post-Neoadjuvant Therapy: A Comprehensive Review

“…A meta-analysis by Jang et al found that ymrTRG scores of 1–2, which correspond to complete or good radiological regression, had a sensitivity of 70–71% and a specificity of 62–68% [ 58 , 59 ]. Moreover, the inter-reader agreement of ymrTRG is highly variable, with kappa values ranging from 0.25 to 0.8 [ 60 , 61 , 62 ].…”

Rectal MRI Interpretation After Neoadjuvant Therapy

“…41 However, there is poor association between mrTRG and pathologic TRG. [44][45][46] MrTRG has a modest sensitivity of 74% for the detection of complete response. 44 Nonetheless, this system is widely used in the United Kingdom, Canada, and some parts of the United States.…”

“…4). 41 However, there is poor association between mrTRG and pathologic TRG 44–46 . MrTRG has a modest sensitivity of 74% for the detection of complete response 44 .…”