Published online May 28, 2020. doi: 10.3748/wjg.v26.i20.2657
Peer-review started: January 14, 2020
First decision: February 29, 2020
Revised: April 30, 2020
Accepted: May 13, 2020
Article in press: May 13, 2020
Published online: May 28, 2020
The management of rectal cancer patients is mainly based on the use of the magnetic resonance imaging (MRI) technique as a diagnostic tool for both staging and restaging. After treatment, to date, the evaluation of complete response is based on the histopathology assessment by using different tumor regression grade (TRG) features (e.g., Dworak or Mandard classifications). While from the radiological point of view, the main attention for the prediction of a complete response after chemotherapy treatment focuses on MRI and the potential role of diffusion-weighted images and perfusion imaging represented by dynamic-contrast enhanced MRI. The main aim is to find a reliable tool to predict tumor response in comparison to histopathologic findings.
To investigate the value of dynamic contrast-enhanced perfusion-MRI parameters in the evaluation of the healthy rectal wall and tumor response to chemo-radiation therapy in patients with local advanced rectal cancer with histopathologic correlation.
Twenty-eight patients with biopsy-proven rectal adenocarcinoma who underwent a dynamic contrast-enhanced MR study performed on a 1.5T MRI system (Achieva, Philips), before (MR1) and after chemoradiation therapy (MR2), were enrolled in this study. The protocol included T1 gadolinium enhanced THRIVE sequences acquired on axial planes. A dedicated workstation was used to generate color permeability maps. Region of interest was manually drawn on tumor tissue and normal rectal wall, hence the following parameters were calculated and statistically analyzed: Relative arterial enhancement (RAE), relative venous enhancement (RVE), relative late enhancement (RLE), maximum enhancement (ME), time to peak and area under the curve (AUC). Perfusion parameters were related to pathologic TRG (Mandard's criteria; TRG1 = complete regression, TRG5 = no regression).
Ten tumors (36%) showed complete or subtotal regression (TRG1-2) at histology and classified as responders; 18 tumors (64%) were classified as non-responders (TRG3-5). Perfusion MRI parameters were significantly higher in the tumor tissue than in the healthy tissue in MR1 (P < 0.05). At baseline (MR1), no significant difference in perfusion parameters was found between responders and non-responders. After chemo-radiation therapy, at MR2, responders showed significantly (P < 0.05) lower perfusion values [RAE (%) 54 ± 20; RVE (%) 73 ± 24; RLE (%): 82 ± 29; ME (%): 904 ± 429] compared to non-responders [RAE (%): 129 ± 45; RVE (%): 154 ± 39; RLE (%): 164 ± 35; ME (%): 1714 ± 427]. Moreover, in responders group perfusion values decreased significantly at MR2 [RAE (%): 54 ± 20; RVE (%): 73 ± 24; RLE (%): 82 ± 29; ME (%): 904 ± 429] compared to the corresponding perfusion values at MR1 [RAE (%): 115 ± 21; RVE (%): 119 ± 21; RLE (%): 111 ± 74; ME (%): 1060 ± 325]; (P < 0.05). Concerning the time-intensity curves, the AUC at MR2 showed significant difference (P = 0.03) between responders and non-responders [AUC (mm2 × 10-3) 121 ± 50 vs 258 ± 86], with lower AUC values of the tumor tissue in responders compared to non-responders. In non-responders, there were no significant differences between perfusion values at MR1 and MR2.
Dynamic contrast perfusion-MRI analysis represents a complementary diagnostic tool for identifying vascularity characteristics of tumor tissue in local advanced rectal cancer, useful in the assessment of treatment response.
Core tip: The management of rectal cancer has changed in the past years. The possibility to achieve a complete response after chemo-radiotherapy and the results of non-surgical management of the disease (“watch and wait” approach) highlighted the need to obtain an accurate assessment of complete response. In this setting, dynamic-contrast-enhanced magnetic resonance imaging, which provides valuable information about the degree of angiogenesis, is considered a promising functional tool. This study aimed to assess dynamic-contrast enhanced-parameters differences between the tumor tissue and the healthy rectal wall, both before and after chemo-radiotherapy, and to find a possible correlation with pathological findings and TNM stage.