Rectal cancer staging provides information about the extent of disease, helps to determine the prognosis, guides management, and assesses response to therapy.
Dukes summarized current opinion, stating that in its earliest stages, rectal cancer begins as an epithelial proliferation rising from the surface and that carcinoma develops from a preexisting adenoma.
The cancer metastasizes through the bowel wall to the lymphatics.
Cases in which the carcinoma is limited to the wall of the rectum were designated A.
Those in which the cancer has spread by direct continuity to the extrarectal tissue were designated B.
Cases in which metastases are present in the regional lymph nodes were called C.
For B lesions, the subscript designation “1” for lesions that have extended into, but not through the muscularis propria and “2” for tumors that have penetrated the muscularis propria.
Duke classification by modified Astler–Coller (MAC) classification is listed below:
Type A—Lesions limited to the mucosa
Type B1—Lesions extending into the muscularis propria, but not penetrating it, with negative nodes
Type B2—Lesions penetrating the muscularis propria, with negative nodes
Type C1—Lesions extending into the muscularis propria, but not penetrating it, with positive nodes.
Type C2—Lesions penetrating the muscularis propria with positive nodes
The yearly survival of patients demonstrated a progressive decline proportional to the depth of penetration of the colonic wall.
Turnbull designated stage D to identify tumors that have metastasized to the liver, lung, bone,, and adjacent organs.
In addition, the histologic grade of each tumor was recorded even though it was not included in pathologic staging.
The American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (IUCC) introduced a cancer staging system based on local tumor depth of invasion (T), the presence and number of nodal metastases (N), and the presence of distant metastases (M).
The TNM criteria for colorectal cancer are used most commonly by clinicians today.
Tumor, Node, Metastases (TNM) Classification of Colorectal Cancer:
T-Primary tumor
Tx Primary tumor cannot be assessed
T0 No evidence of primary tumor
Tis Carcinoma in situ: intraepithelial or invasion of lamina propria
T1 Tumor invades submucosa
T2 Tumor invades muscularis propria
T3 Tumor invades through muscularis propria into subserosa or into non-peritonealized pericolic or perirectal tissues
T4 Tumor directly invades other organs or structures and/or perforates visceral peritoneum.
N-Regional lymph nodes
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis in one to three regional lymph nodes
N2 Metastasis in four or more regional lymph nodes
M-Distant metastasis
MX Distant metastasis cannot be assessed
M0 No distant metastasis
M1 Distant metastasis
Stage Grouping
Stage T N M , Dukes , Dukes-MAC
0 Tis N0 M0 — —
I T1 N0 M0, A, A
T2 N0 M0, A, B1
IIA T3 N0 M0, B , B2
IIB T4 N0 M0, B, B3
IIIA T1, T2 N1 M0, C , C1
IIIB T3, T4 N1 M0, C , C2/C3
IIIC Any T N2 M0, C , C1/C2/C3
IV Any T Any N M1 — D
The 1932 Duke’s staging system, is based on histopathology alone,
The TNM staging system permits assessment of T, N, and M categories by other clinical criteria including physical examination, imaging, endoscopy, and/or surgical exploration.
Rectal cancer staging has assumed additional roles, namely, the determination of optimal therapy and assessment of response to therapy.
Therapy is based on staging information include curative versus palliative operation, radical versus local excision, preoperative chemoradiation therapy, and postsurgical adjuvant therapy.
The rectum extends proximally from the rectosigmoid junction where the taenia coli coalesce distally to the anorectal ring.
The rectum is divided into thirds beginning at the anorectal ring at 3.5 cm: lower rectum 3.5 cm to 7.5 cm; midrectum 7.5 cm to 12 cm; upper rectum 12 cm to 16 cm.
The most proximal rectum is intraperitoneal.
The middle and lower rectum is partially or wholly extraperitoneal.
Cancers of the upper rectum (above 12 cm) behave like colon cancers with regard to recurrence.
For upper third lesions, resection with partial mesorectal excision generally is accepted surgical therapy.
Treatment for middle and lower third rectal cancers in the absence of distant metastases varies.
Proctosigmoidectomy with total mesorectal excision (TME) is recommended in most cases. for middle and lower third rectal cancers,
Local excision may be appropriate for selected early distal rectal cancers.
Chemoradiation may be given preoperatively or postoperatively.
With digital rectal exam the size, location, and degree of fixation of most low and some middle third rectal tumors can be detected and provides a rough estimate of local rectal cancer stage.
Endoscopy is done to detect the tumor and obtain tissue for histologic diagnosis, to assess tumor dimensions, distance from the anal sphincter, and relation to landmarks such as the prostate or vagina with a view toward future surgery.
The entire large intestine is examined by colonoscopy, to exclude synchronous lesions.
Carcinoembryonic antigen (CEA) is measured as a baseline.
The best studies for the determination of T classification and N status are endorectal ultrasound (EUS) and magnetic resonance imaging (MRI).
EUS is commonly used to determine the extent of local wall penetration for middle- and lower-third rectal cancers.
An ultrasonic staging system is based on depth of invasion and lymph node positivity.
EUS can help determine whether downstaging after preoperative chemoradiation for extraperitoneal locally advanced rectal cancer predicts improved outcome.
MRI is highly useful in defining the stage of rectal cancer.
High-resolution MRI images obtained in multiple planes with high soft tissue contrast resolution provides detailed information concerning the relation of the tumor to the circumferential resection margin and adjacent structures, extramural venous invasion, lateral pelvic lymphadenopathy, and peritoneal surface involvement by tumor.
PET scanning accurately changes the stage or appropriately alter the therapy in almost a third of patients with advanced primary rectal cancer.
Conventional CT detects local invasion of neighboring structures and distant metastases.
In metastatic carcinomas, lactate levels are significantly higher and glucose levels significantly lower than those in nonmetastatic carcinomas.