*2.6.2 Assessing T-stage*

Determination of the T-stage (**Figure 7**) depends on the correct visualization of each individual layer in compliance with the MR-protocol. T category is characterized by the depth of tumor penetration into the rectal wall and extramural spread into the mesorectum and adjacent structures.

**65**

T3 to T3a, b, c, d.

**Figure 7.**

*images).*

**Figure 6.**

*Horvat et al. [12].*

invasion as measured by MRI and histopathology.

tumor, but the heterogeneity in survival values is high:

*Role of Magnetic Resonance Imaging in Patients with Rectal Cancer*

in T1 and T2 rectal tumors is an intact external muscularis layer, which is identified as a hypointense thin line surrounding the rectum. T3-tumors grow through the external muscularis into the surrounding mesorectum, important is to classify

*Different T stages of rectal cancer: T2 rectal cancer (left) and T3d rectal cancer (right) (axial T2 weighted MR* 

*Rectal tumor high. Source: MRI of Rectal Cancer: Tumor Staging, Imaging Techniques, and Management",* 

Consistency between MRI and histopathology in determining the T-stage was initially studied by Brown et al. [3], who found a 94% match between MRI and pTstage. The MERCURY multicentre study directly compared the extramural depth of

Numerous histopathological studies have shown the importance of the T-stage. The T3 subclassification was developed because the majority of patients have a T3

*DOI: http://dx.doi.org/10.5772/intechopen.94868*

*Role of Magnetic Resonance Imaging in Patients with Rectal Cancer DOI: http://dx.doi.org/10.5772/intechopen.94868*

### **Figure 6.**

*Colorectal Cancer*

recurrence.

from the disease.

ing the tumor response:

• mrTRG (tumor regression)

• ymrT (depth of invasion)

• ymrN (nodal status).

*2.6.1 Assessing tumor high*

Low rectal cancer:

Mid rectal cancer:

High rectal cancer:

engagement.

*2.6.2 Assessing T-stage*

• CRM (circumferential resection margin)

Rectal cancer can be divided (**Figure 6**) into:

Distal border is 0–5 cm from the anorectal angle.

Distal border is 5–10 cm from the anorectal angle.

Distal border is 10–15 cm from the anorectal angle.

into the mesorectum and adjacent structures.

Involvement of the intersphincteric plane, external sphincter and levator musculature should be assessed. Low cancer localization increases the risk of CRM

Determination of the T-stage (**Figure 7**) depends on the correct visualization of each individual layer in compliance with the MR-protocol. T category is characterized by the depth of tumor penetration into the rectal wall and extramural spread

• EMVI- ymrEMVI

continuation with chemotherapy with intensification and/or experimental pharmacotherapy and change of mrTRG to a prognostically better group.

• the third MRI is for the group waiting for surgery and MRI is used to monitor

As already mentioned, we have to separate some imaging markers on the preand posttreatment studies that are essential for predicting response and outcome

In the first group is the pretreatment MRI and the imaging features for predict-

• Tumor height - low rectal cancer is more likely to have a bad response;

• EMVI - the presence of mrEMVI is associated with a worse prognosis.

In the second groups is the posttreatment MRI and evaluation of the post-

• T stage- T1, T2, T3a, T3b are more likely to have a good response;

• Tumor height from the intersphincteric line to the distal TME line

therapeutic response (used prefix "y"- after neoadjuvant therapy):

**64**

*Rectal tumor high. Source: MRI of Rectal Cancer: Tumor Staging, Imaging Techniques, and Management", Horvat et al. [12].*

### **Figure 7.**

*Different T stages of rectal cancer: T2 rectal cancer (left) and T3d rectal cancer (right) (axial T2 weighted MR images).*

in T1 and T2 rectal tumors is an intact external muscularis layer, which is identified as a hypointense thin line surrounding the rectum. T3-tumors grow through the external muscularis into the surrounding mesorectum, important is to classify T3 to T3a, b, c, d.

Consistency between MRI and histopathology in determining the T-stage was initially studied by Brown et al. [3], who found a 94% match between MRI and pTstage. The MERCURY multicentre study directly compared the extramural depth of invasion as measured by MRI and histopathology.

Numerous histopathological studies have shown the importance of the T-stage. The T3 subclassification was developed because the majority of patients have a T3 tumor, but the heterogeneity in survival values is high:

