Onkologie. 2017:11(2):61-65 | DOI: 10.36290/xon.2017.013

The significance of magnetic resonance imaging rectal cancer

Šárka Bohatá

Klinika radiologie a nukleární medicíny Fakultní nemocnice Brno a Lékařská fakulta Masarykovy univerzity Brno

High-resolution magnetic resonance imaging (MRI) plays a pivotal role and has become almost mandatory in the pretreatment

assessment of primary rectal cancer. The high soft-tissue contrast of MRI accurately assesses the extramural tumor spread and

relation to mesorectal fascia and the sphincter complex and also the surrounding pelvic anatomy, and is increasingly being used

to evaluate tumor resectability in patients with rectal cancer and to determine which patients can be treated with surgery alone

and which will require radiation therapy to promote tumor regression. MRI is currently the only imaging modality that is highly

accurate in predicting whether or not it is likely that a tumorfree margin can be achieved and thus provides important information

for planning of an effective therapeutic strategy, especially in patients with advanced rectal cancer. The accuracy of MRI in

assessing mesorectal lymph nodes remains moderate, as there are no reliable criteria to assess nodal involvement. In patients

with rectal cancer who have received concurrent chemotherapy and radiation therapy before surgery, MRI has lower accuracy

in prediction of the pathologic stage owing to overstaging or understaging. The factors related to this problem include fibrosis,

desmoplastic reaction, edema, inflammation, and viable tumor nets at a fibrotic scar from a previous tumor. Reassessment of MRI

scans after preoperative therapy has implications for surgical planning, the timing of surgery, sphincter preservation, deferral of

surgery for good responders, and development of further preoperative treatments for radiologically identified poor responders.

To identify patients with true complete pathological response before surgical resection remains a challenge.

Keywords: magnetic resonance imaging, rectal cancer, staging, restaging, therapy response

Published: May 1, 2017  Show citation