MRI Evaluation of the Response of Rectal Cancer to Neoadjuvant Chemoradiation Therapy

Abstract

MRI plays a critical role in the staging and restaging of rectal cancer. Although newly diagnosed early-stage rectal cancers may immediately be amenable to surgical resection, patients with advanced disease first undergo neoadjuvant therapy that consists of a combination of chemotherapy and radiation therapy. Evaluation of rectal cancer after neoadjuvant therapy is best performed with MRI, given its superior soft-tissue contrast and its ability to allow multiplanar imaging and functional evaluation. In this setting, MRI allows accurate evaluation of primary tumor staging, which is determined on the basis of the depth of invasion within and through the rectal wall and the involvement of adjacent organs. MRI can also be used to evaluate posttreatment morphologic components within the tumors, including fibrosis and mucinous changes that have been shown to correlate with the response to treatment. Additional features such as the circumferential resection margin and extramural vascular invasion-factors shown to affect prognosis and local recurrence-are also assessed before and after therapy. Functional assessment with diffusion-weighted MRI and perfusion MRI plays a role in predicting tumor aggressiveness and the likelihood of response to treatment, as well as the extent of residual tumor after therapy. Lymph node staging is also performed at MRI, with assessment of not only lymph node size but also the internal architecture and signal intensity characteristics. ©

Dual-energy CT parameters in correlation to MRI-based apparent diffusion coefficient: evaluation in rectal cancer after radiochemotherapy

“…CT can be used for imaging of the primary tumor; however, therapy response to RCT can only be visualized indirectly by size measurement as the tumor perfusion and thus its vitality cannot be quantified in single-phase examinations with conventional CT systems (11,12). This drawback of CT could be overcome with dual-energy CT (DE-CT) systems, which have found widespread application in clinical routine in recent years (13).…”

Rectal cancer: a methodological approach to matching PET/MRI to histopathology

“…Magnetic resonance imaging (MRI) of the pelvis is fundamental to the staging and restaging of patients with adenocarcinoma of the rectum [ 1 – 4 ]. MRI is applied to assess markers, i.e.…”

Invited Commentary on “MRI Evaluation of the Response of Rectal Cancer to Neoadjuvant Chemoradiation Therapy”

“…The article by Kalisz et al (5) in this issue of RadioGraphics provides an excellent, well-written comprehensive review of MRI in the posttherapeutic response assessment of rectal cancer, enriched with several excellent multimodality images. The article begins by providing an over-This copy is for personal use only.…”

“…As alluded to in the article by Kalisz et al (5), accurate local staging is paramount for allocating patients to the most suitable treatment and cannot be emphasized enough. The results of several studies, including the MERCURY trial, have shown high accuracy of a high-resolution T2-weighted sequence in predicting the risk of circumferential resection margin involvement, which is an independent risk factor for local recurrence (6).…”

“…Investigators have shown that pretreatment low ADC and high K trans correlated with a better treatment response and may be used in predicting treatment response on an individual basis (7). As emphasized by Kalisz et al (5), the importance of using the same technique, sequences, and preferably magnet strength before and after therapy cannot be overstated, to optimize comparison between studies as well as reliable tumor response assessment. A meta-analysis assessing multiparameteric MRI in posttherapeutic assessment of rectal cancer showed a lack of standardization in hardware, software, and protocols as a major limitation of clinical application in reliable assessment of tumor response (8).…”