Staging

The ideal pre-operative assessment assigns patients with rectal cancer into three distinct groups: patients with early stage localised lesions where surgery alone would potentially be curative; patients with locally advanced cancers who are likely to benefit from pre-operative or adjuvant therapy; and those with advanced or metastatic disease where surgery might be modified or avoided. The presence of associated comorbidities will also influence the choice of treatment.

Patients with rectal cancer should undergo a clinical examination, blood sampling including CEA, endoscopic exam with biopsy specimen, endorectal ultrasound (EUS), magnetic resonance (MRI) or computed tomography (CT) and chest X-ray.

EUS allows clear visualisation of the layers of the rectal wall and thus enables the depth of invasion to be accurately measured. Its accuracy varies from 82 to 93% in terms of T factor in the literature. Assessment of lymph node status is less reliable, with an accuracy of 65-81% (EUS staging is defined yTN).

Inflammatory changes from previous biopsies or irradiation may reduce the diagnostic accuracy of this method whereas a stenotic lesion may limit access of the probe [6-8].

RMI or CT scans of the abdomen and pelvis are recommended as they provide additional information about the extent of the disease such as the presence of distal metastatic disease or pelvic organ infiltration.

MRI with endorectal coil exhibits similar accuracy to EUS and is superior to conventional CT in pre-operative assessment of depth of invasion of rectal cancer (accuracy 81 vs. 65%) and adjacent organ invasion. Furthermore, MR enables more accurate identification of nodal involvement than other imaging modalities [9-12].

Unfortunately, MRI loses these advantages in restaging irradiated tumours (accuracy 52% for T factor and 68% for N factor), with poor agreement with pathological stage of T and N factor while MR

Table 1. AJCC staging of rectal cancer [16]

Stage

T

N*

M

Stage 0

In situ

0

0

Stage I

1-2

0

0

Stage II A

3

0

0

Stage II B

4

0

0

Stage III A

1-2

1

0

Stage III B

3-4

1

0

Stage III C

Any T

2

0

Stage IV

Any T

Any N

1

*A tumour nodule in the pericolorectal adipose tissue of a primary carcinoma without histologic evidence of residual lymph node in the nodule is classified in the pN category as a regional lymph node metastasis if the nodule has the form and smooth contour of lymph node. If the nodule has an irregular contour, it should be classified in the T category and also coded as V1 (microscopic venous invasion) or as V2 (if it was grossly evident), because there is a strong likelihood that it represents venous invasion

*A tumour nodule in the pericolorectal adipose tissue of a primary carcinoma without histologic evidence of residual lymph node in the nodule is classified in the pN category as a regional lymph node metastasis if the nodule has the form and smooth contour of lymph node. If the nodule has an irregular contour, it should be classified in the T category and also coded as V1 (microscopic venous invasion) or as V2 (if it was grossly evident), because there is a strong likelihood that it represents venous invasion keeps reliable prediction of clear circumferential resection margins. It is probable that most of the inaccuracy in both T and N stages is caused by over-staging. Thickening of the rectal wall after radiation by marked fibrosis, peritumoral infiltration of inflammatory cells and vascular proliferation cannot be completely differentiated from viable residual tumour by this technique [13,14].

During the past few years, FDG-PET has been studied in the assessment of chemoradiation response of locally advanced rectal cancer, showing good results with a negative predictive value of 100% vs. MRI or CT and high efficacy in detection of metastatic disease [15].

We should not forget that if removal of the rectum is contemplated, early consultation with an enteros-tomal therapist should be recommended for pre-operative marking of the site and for pre-operative assessment of the patient (Table 1).

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