Profiling of rectal cancers MRI in pathological complete remission states after neoadjuvant concurrent chemoradiation therapy

Analysis of influencing factors of no/low response to preoperative concurrent chemoradiotherapy in locally advanced rectal cancer

“…After 8 weeks of CCRT, we performed a preoperative MRI examination and compared with images before CCRT to evaluate the changes of the primary tumor, local positive lymph nodes and circumferential resection margin (CRM). Since the MRI results cannot fully reflect the tumor pathological regression status [25], especially its limitation in distinguishing residual tumor from surrounding fibrosis [26][27][28], we evaluated the rectal cancer regression grade (RCRG) of the enrolled patients by referring to the quantification standard of histologic regression of rectal cancer after irradiation of Wheeler JM et al [29]. Within this scoring criterion, the regression of rectal tumors was classified into three levels: RCRG 1: Sterilization or only microscopic foci of adenocarcinoma remaining, with marked fibrosis; RCRG 2: Marked fibrosis but macroscopic disease present; RCRG 3: Little or no fibrosis, with abundant macroscopic disease.…”

Postchemoradiation magnetic resonance imaging circumferential resection margin predicts treatment failure after multidisciplinary directed sphincter preservation in low rectal cancer

“…A line called “MRI low pelvic line (mrLPL)” was drawn 1 cm above the level of the anorectal junction on the coronal image (Figure 1). This line was previously shown to correlate with the upper end of the intersphincteric plane 13 . MRI circumferential resection margin (mrCRM) was defined as “free” when the fat signal was detected between the tumor and mesorectal fascia (MRF); “abutting” when no fat signal was detected between the tumor and MRF, but there was no direct invasion and thickening of MRF; and “definite invasion” when the tumor showed direct invasion or thickening of the MRF (Figure 2).…”

“…This line was previously shown to correlate with the upper end of the intersphincteric plane. 13 MRI circumferential resection margin (mrCRM) was defined as "free" when the fat signal was detected between the tumor and mesorectal fascia (MRF); "abutting" when no fat signal was detected between the tumor and MRF, but there was no direct invasion and thickening of MRF; and "definite invasion" when the tumor showed direct invasion or thickening of the MRF (Figure 2). MRI tumor regression grade (mrTRG) was defined as follows: mrTRG1, no residual tumor; mrTRG2, the predominance of fibrosis with minimal residual tumor; mrTRG3, residual tumor with the predominance of fibrosis; mrTRG4, predominantly tumor tissue with minimal fibrosis; and mrTRG5, no response.…”

ACR Appropriateness Criteria® Staging of Colorectal Cancer: 2021 Update

“…Standard posttreatment MRI sequences include thin cut (3-4 mm) T2-weighted nonfat-saturated images, pre-and postcontrast images, and diffusion-weighted sequence with b values up to 800 to 1,000, sometimes higher. In contrast to PET/CT, MRI tends to overestimate residual viable tumor and underestimate pathological complete response of the primary, and research into specific imaging findings/sequences to optimize this modality and identify "complete responders" are ongoing [80][81][82].…”