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

Abstract

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.

Magnetic resonance tumour regression grade and pathological correlates in patients with rectal cancer

“…An independent association between mrTRG categories and postoperative survival in patients with rectal cancer has been demonstrated. With this background, attempts are being made to use the mrTRG system to stratify patients after CRT and guide good responders to less aggressive therapeutic options; however, there is a paucity of information regarding the pathological correlation with mrTRG. This study aimed to investigate the pathological characteristics of mrTRG and their implications for patient management following CRT for locally advanced rectal cancer.…”

Poorer Oncologic Outcome of Good Responders to PCRT With Remnant Lymph Nodes Defies the Oncologic Paradox in Patients With Rectal Cancer

“…MrTRG and other MRI-measured parameters such as circumferential resection margin are associated with oncologic outcome, 5,17 as was in our data ( Table 1); there remains a limitation in assessing the tumor response to PCRT. 18 Post-PCRT evaluation of response is particularly tricky regarding nodal status, as LNs become smaller and even disappear after PCRT. 19,20 Considering the limitation in current diagnostic methods in assessing post-PCRT clinical stage, we should also consider the oncologic outcomes after standard radical resection in deciding the following surgical strategies.…”

The Immunoscore in the Clinical Practice of Patients with Colon and Rectal Cancers

“…All these findings suggested the potential utility of the ISB to frame the therapeutic decision of conservative surgery. To date however, the main concern restricting the extent of the W&W strategy is local relapse (often referred as local regrowth) that develops during the first 12 months period (60). In a limited multicenter series of patients treated by W&W, we observed that almost one-third of them presented with a ISB High.…”