**2.5 Treatment options**

Before discussing the imaging of rectal cancer one should understand the treatment options for the disease. The ideal prognostic stage allows selection of the patient according to the risk of local and/or systemic recurrence. This leads to three main treatment options:


Planning and decision making are listed in the European [8] and Nord-American guidelines [9].

Main goal is to achieve downstaging and downsizing of the tumor and therefore optimal mesorectal excision. This is possible with neoadjuvant therapy and it has a leading role in treatment of rectal cancer. Synchronous to better therapeutical options many imaging markers for response measurement are found out.

In order to objectively measure the rate of tumor response to this therapy, several systems called histopathological tumor regression grades (pTRG) have been developed, the most commonly used being those of Dworak [10] and Mandard [11] Both systems determine the response to treatment based on the residual/residual cells in the fibrous stroma, and the gradation is between "no response" to "complete response". A pathological complete response (pCR) is defined as "no residual tumor cells in the material". A novel radiological method for tumor response has been developed based on pCR - magnetic resonance imaging of the tumor response tumor regression grade (mrTRG) [7] MRI can be used to predict a favorable response and to assess the extent of subsequent treatment.

Therefore we can use some imaging predictors on pretreatment (primary) MRIscan and on posttreatment (secondary) MRI-scan. This is how we could reach out to the second principle of rectal cancer staging - prognostic stage grouping.

### **2.6 MRI of rectal cancer**

The main imaging modality for local staging of rectal cancer is magnetic resonance imaging (MRI), as it provides the most accurate information about important prognostic markers that could affect the choice of treatment. In addition, there are many new studies on the role of MRI in assessing the response after neoadjuvant radiation therapy.

Тechnical parameters for MRI: 1,5 T or 3 T, FOV (160 x 160 mm, 256 x 256 matrix), 0.6 x 0.6 x 3 mm, high-resolution image (1 mm 3 voxel size), sequences: first series - T2-weighted sagittal, turbo spin-echo sequences for tumor identification, second series – axial T2 to the whole pelvis, third series - T2-weighted thinsection axial through the neoplasia, and they should be perpendicular to the long axis of the rectum and to the level of the neoplasm (3-mm slices). Addition: for low rectal cancer there is a fourth series - high resolution, coronary images for the levators, the sphincter complex, the intersphincter axis and the relationship to the rectal wall. Follow-up MRI after treatment follows the same protocol.

Diffusion-weighted imaging (DWI) images of magnetic resonance show the random movement of water molecules in the body. The degree of water restriction in biological tissues is directly proportional to the tissue cellularity and integrity of the cell membrane. Therefore, the contrast of tissues at D The apparent diffusion coefficient (ADC) is recalculated by the DWI, using these two techniques to compare different tissue compartments depending on the cell composition. Evaluates the response to treatment. DWI could be useful in the primary detection of rectal cancer and lymph nodes, but not for follow-up assessment or measurement of tumor regression, incl. mrTRG.

**63**

**Figure 5.**

*Mucosal layers of rectal wall (axial T2 weigted MR image).*

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

Gadolinium-enhanced MRI is not recommended.

MRI has the ability to distinguish each individual layer of mucosa and muscle due to their different signaling characteristics. For this purpose, the T2 sequence

• Muscularis propria - a double layer of inner circular and outer longitudinal layer, the latter having an irregular appearance due to the passing vessels

• Mesorectal fascia - a thin hypointense band surrounding all of the above

*Patients with rectal cancer will receive a series of MRIs during the course of their* 

• the initial (primary) MRI will guide whether neoadjuvant therapy is needed, will guide the operative plan, and factors such as mrEMVI will determine the

• the secondary MRI follows the neoadjuvant therapy, and the response is assessed by mrTRG. In patients with a good mrTRG response [1, 2], it is possible to wait with surgery or reduce the volume of the operation or continue with radical surgery. The first two options potentially lead to the preservation of the integrity of the rectum, but additional MR examinations are needed. In case of a weak response (mrTRG4–5) it is possible to choose surgery or

• Perirectal adipose tissue/mesorectum - high signal tissue

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

• Mucosa - fine hypointense line

type of neoadjuvant therapy

• Submucosa - thicker hyperintense layer

is used:

(**Figure 5**)

*treatment:*

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

Gadolinium-enhanced MRI is not recommended.

MRI has the ability to distinguish each individual layer of mucosa and muscle due to their different signaling characteristics. For this purpose, the T2 sequence is used:

• Mucosa - fine hypointense line

*Colorectal Cancer*

main treatment options:

• Surgery alone,

American guidelines [9].

**2.6 MRI of rectal cancer**

radiation therapy.

• neoadjuvant therapy before surgery and

• palliative pharmacotherapy/radiotherapy alone.

response and to assess the extent of subsequent treatment.

patient according to the risk of local and/or systemic recurrence. This leads to three

Planning and decision making are listed in the European [8] and Nord-

In order to objectively measure the rate of tumor response to this therapy, several systems called histopathological tumor regression grades (pTRG) have been developed, the most commonly used being those of Dworak [10] and Mandard [11] Both systems determine the response to treatment based on the residual/residual cells in the fibrous stroma, and the gradation is between "no response" to "complete response". A pathological complete response (pCR) is defined as "no residual tumor cells in the material". A novel radiological method for tumor response has been developed based on pCR - magnetic resonance imaging of the tumor response tumor regression grade (mrTRG) [7] MRI can be used to predict a favorable

Main goal is to achieve downstaging and downsizing of the tumor and therefore optimal mesorectal excision. This is possible with neoadjuvant therapy and it has a leading role in treatment of rectal cancer. Synchronous to better therapeutical options many imaging markers for response measurement are found out.

Therefore we can use some imaging predictors on pretreatment (primary) MRIscan and on posttreatment (secondary) MRI-scan. This is how we could reach out to

The main imaging modality for local staging of rectal cancer is magnetic resonance imaging (MRI), as it provides the most accurate information about important prognostic markers that could affect the choice of treatment. In addition, there are many new studies on the role of MRI in assessing the response after neoadjuvant

Тechnical parameters for MRI: 1,5 T or 3 T, FOV (160 x 160 mm, 256 x 256 matrix), 0.6 x 0.6 x 3 mm, high-resolution image (1 mm 3 voxel size), sequences: first series - T2-weighted sagittal, turbo spin-echo sequences for tumor identification, second series – axial T2 to the whole pelvis, third series - T2-weighted thinsection axial through the neoplasia, and they should be perpendicular to the long axis of the rectum and to the level of the neoplasm (3-mm slices). Addition: for low rectal cancer there is a fourth series - high resolution, coronary images for the levators, the sphincter complex, the intersphincter axis and the relationship to the

Diffusion-weighted imaging (DWI) images of magnetic resonance show the random movement of water molecules in the body. The degree of water restriction in biological tissues is directly proportional to the tissue cellularity and integrity of the cell membrane. Therefore, the contrast of tissues at D The apparent diffusion coefficient (ADC) is recalculated by the DWI, using these two techniques to compare different tissue compartments depending on the cell composition. Evaluates the response to treatment. DWI could be useful in the primary detection of rectal cancer and lymph nodes, but not for follow-up assessment or measurement of tumor regression, incl. mrTRG.

rectal wall. Follow-up MRI after treatment follows the same protocol.

the second principle of rectal cancer staging - prognostic stage grouping.

**62**


*Patients with rectal cancer will receive a series of MRIs during the course of their treatment:*


**Figure 5.** *Mucosal layers of rectal wall (axial T2 weigted MR image).*

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 recurrence.

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

In the first group is the pretreatment MRI and the imaging features for predicting the tumor response:


In the second groups is the posttreatment MRI and evaluation of the posttherapeutic response (used prefix "y"- after neoadjuvant therapy):

