MRI-PATHOLOGICAL PARALLELS WITH THE COMPLETE TUMOR RESPONSE TO NEOADJUVANT CHEMORADIATION TREATMENT OF RECTAL CANCER

Abstract

Purpose of the study. To study the patterns of forming an MRI picture of a complete pathological morphological response (pCR) of colorectal cancer a’ er neoadjuvant chemoradia on therapy (NHLT) based on comparisons with the pathomorphological picture. Patients and methods. Among 130 patients with locally advanced colorectal cancer who received a combined treatment with NHL at A. Tsyb MRRC clinic — a Branch of HMRRC of the Ministry of Health of the Russian Federation within the period 2012–2017 thirteen patients were selected for the study, in whom pCR was achieved, according to the pathological analysis of surgical specimen. MRI was performed on all patients before the NHLT and atier the end (atier 6–10 weeks) of treatment. We analyzed the MRI fi ndings from case histories (prospective assessment) on degree of tumor regression (mrTRG) using a fi ve-point grading scale. Ten of these patients had MRI examinations available for re-review (retrospective assessment), which allowed for a qualitate ve assessment of the signal intensity in T2 mode on a nominal scale, according to which low, medium, moderately elevated and high MR signals were discerned; signal localization was determined relative to the intestinal lumen with conditional selection of the inner and outer layer of the wall, and the outer contour was charactezied (smooth or uneven due to hypointense spicules). The obtained data on the localization of the MR signal of varying intensity were compared with the data of the pathological description of the operating drugs.Results. A prospective MRI assessment of pCR in 77% of cases corresponded to TRG2 and in 92% — y N0. Macroscopically, the pCR in all patients had an appearance of an ulcerative defect of the intestinal wall, to which on T2-WI in 80% of cases corresponded to a moderately elevated MR signal from the inside of the wall, due to necroti c changes and granulations, and in 100% of cases — a low MR signal from the outer layer of the intestinal wall, caused by a more mature connective tissue, the outer contour in 50% of cases was tight due to the desmoplastic reaction; hypo-intensive inclusions corresponded to lime deposits, and “mucous lakes” — inclusions with high signal intensity and clear contours.Conclusion The features of forming MRI picture of the pCR are due to a range of radiation pathomorphosis manifestations, including destructive, regenera ve and infl ammatory processes in the tumor stroma.