MAJOR CHANGES IN THE STAGING OF COLORECTAL CANCER

Dongfeng Tan, MD

Adopted from the 7^th Edition of AJCC, please read the original book chapter for more detailed information

I.  Primary Tumor

Circumferential Resection Margins. It is essential that accurate pathologic evaluation of the CRM adjacent to the deepest point of the tumor invasion be performed. The CRM is the surgically dissected nonperitonealized surface of the specimen. It corresponds to any aspect of the colorectum that is not covered by a serosal layer of mesothelial cells and must be dissected from the retroperitoneum or sub-peritoneum in order to remove the viscus.

For resection cases, the resection (R) codes should be given for each procedure:

• R0 – Complete tumor resection with all margins histologically negative
• R1 – Incomplete tumor resection with microscopic surgical resection margin involvement (margins grossly uninvolved)
• R2 – Incomplete tumor resection with gross residual tumor that was not resected (primary tumor, regional nodes, macroscopic margin involvement)

Designation of Primary Tumor (T)

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 the muscularis propria into pericolorectal tissues

T4a        Tumor penetrates to the surface of the visceral peritoneum

T4b        Tumor directly invades or is adherent to other organs or structures

*Note: The definition of in situ carcinoma – pTis – includes cancer cells confined within the glandular basement membrane (intraepithelial) or lamina propria (intramucosal) with no extension through the muscularis mucosae into the submucosa. Neither intraepithelial nor intramucosal carcinomas of the large intestine are associated with risk for metastasis.

Expanded data sets have shown differential prognosis within T4 lesions based on extent of disease. Accordingly, T4 lesions are subdivided as T4a (tumor penetrates the surface of the visceral peritoneum) and as T4b. (Tumor directly invades or is histologically adherent to other organs or structures)

II. Regional Lymph Nodes

It is essential that the total number of regional lymph nodes recovered from the resection specimen be described since that number is prognostically important.

It is recommended to obtain at least 10-14 lymph nodes in radical colon and rectum resections in patients without neoadjuvant therapy.  If the tumor is resected for palliation or in patients who have received preoperative radiation, fewer lymph nodes may be removed or present. A pN0 determination is assigned when these nodes are histologically negative, even though fewer than the recommended number of nodes has been analyzed. However, when fewer than the number of nodes recommended by the College of American Pathologists (CAP) have been found, it is important that the pathologist report the degree of diligence of their efforts to find lymph nodes in the specimen.

Designation of Regional Lymph Nodes (N)

NX      Regional lymph nodes cannot be assessed

N0       No regional lymph node metastasis*

N1       Metastasis in 1-3 regional lymph nodes

N1a     Metastasis in one regional lymph node

N1b     Metastasis in 2-3 regional lymph nodes

N1c     Tumor deposit(s) in the subserosa, mesentery, or nonperitonealized pericolic or perirectal tissues without regional nodal metastasis

N2       Metastasis in four or more regional lymph nodes

N2a     Metastasis in 4-6 regional lymph nodes

N2b     Metastasis in seven or more regional lymph nodes

• The interpretation of very small amounts of detected tumor in regional lymph nodes will continue to be classified as pN0. The prognostic significance of ITCs, defined as single malignant cells or a few tumor cells in microscopical clusters, identified in regional lymph nodes that otherwise would be considered to be negative is still unclear. It should be noted that isolated tumor cells identified on H&E stains alone are also classified as ITC and are annotated in the same fashion as ITC seen on immunohistochemical stains (i.e., pN0(i+);”i”= ”isolated tumor cells”).

The potential importance of satellite tumor deposits is now defined by the new site-specific factor Tumor Deposits (TD) that describes their texture and number. T1-2 lesions that lack regional lymph node metastasis but have tumor deposit(s) will be classified in addition as N1c

• The number of nodes involved with metastasis influences prognosis within both N1 and N2 groups. Accordingly N1 will be subdivided as N1a (metastasis in 1 regional node) and N1b (metastasis in 2-3 nodes), and N2 will be subdivided as N2a (metastasis in 4-6 nodes) and N2b (metastasis in 7 or more nodes)

 III.  Metastatic sites.

Carcinomas of the colon and rectum can metastasize to almost any organ, with the liver and lungs being most commonly involved. Tumor can also spread to other segments of the colon, small intestine, or peritoneum.

Designation of Distant Metastasis (M)

M0       No distant metastasis

M1       Distant metastasis

M1a     Metastasis confined to one organ or site (e.g., liver, lung, ovary, and nonregional node)

M1b     Metastases in more than one organ/site or the peritoneum

 IV.    SUMMARY OF ANTATOMIC STAGE/PROGNOSTIC GROUPS

Stage                  

T                      N                     M                   

0

Tis                    N0                   M0                  

I                      

T1                     N0                   M0                  

T2                     N0                   M0                  

IIA                     

 T3                    N0                   M0                  

IIB                      

  T4a                  N0                   M0                  

IIC                     

  T4b                  N0                   M0                  

IIIA                    

   T1-T2              N1/N1c                M0    

   T1                   N2a                 M0                  

IIIB                   

   T3-T4a               N1/N1c              M0                  

    T2-T3               N2a                 M0                  

    T1-T2               N2b                 M0                  

IIIC                   

    T4a                 N2a                 M0                  

    T3-T4a              N2b                 M0                  

    T4b                 N1-N2               M0                  

IVA                

         Any T               Any N              M1a   

IVB                 

         Any T               Any N              M1b                

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.           The y prefix is used for those cancers that are classified after Neoadjuvant pretreatment (e.g., ypTNM). Patients who have a complete pathologic response are ypT0N0cM0 that may be similar to Stage Group 0 or I. The r prefix is to be used for those cancers that have recurred after a disease-free interval (rTNM).

• In the seventh edition of AJCC Staging Manual, further substaging of Stage II and III has been accomplished, based on new survival and relapse data.

• Stage Group II is subdivided into IIA (T3N0), IIB (T4aN0) and IIC (T4bN0)

• Stage Group III:
• A category of N1 lesions, T4bN1, that was formerly classified as IIIB was found to have outcomes more akin to IIIC and has been reclassified from IIIB to IIIC
• Similarly, several categories of N2 lesions formerly classified as IIIC have outcomes more akin to other stage groups; therefore, T1N2a has been reclassified as IIIA and T1N2b, T2N2a-b, and T3N2a have all been reclassified as IIIB

Tumor Regression Grade.

The pathologic response to preoperative adjuvant treatment should be recorded according to the CAP Protocol for the examination of Specimens from Patients with Carcinomas of the Colon and Rectum), since  neoadjuvant chemoradiation in rectal cancer is  associated with significant treatment effect and often down-staging.