Understanding Staging

Diagnosis

The stage describes the severity of your cancer and helps your doctor determine whether to recommend additional treatment. The most common system for describing the cancer’s stage, called the TMN classification system, uses a numbering system from I to IV.

For colorectal cancer, stages I and II are typically considered “cured” by surgery and require no further treatment. Stage III patients usually receive additional chemotherapy due to cancer cells that have spread to the lymph nodes near the tumor. Stage IV indicates that the cancer has spread to distant organs.

One of the fuzziest areas in colorectal cancer staging is in stages I and II. When traditional testing methods show no spread of the cancer cells, 1 in 5 patients still have a recurrence of their cancer, indicating that cancer metastases present in the nearby lymph nodes simply may not have been detected. Knowing this statistic, a doctor must balance the risks of possibly under treating and chancing a later recurrence or over treating, which could subject a patient to long-term side effects unnecessarily.

New genetic breakthroughs are offering more sensitive methods of determining the spread of cancer cells to help with this difficult treatment decision. This section explains staging in more detail and helps you understand the risks and options for stage I and II colorectal cancer. Topics include:

Staging Criteria
Role of Lymph Nodes in Staging
Imperfections of Current Lymph Node Analysis Method
Breakthroughs in Detecting Colorectal Cancer Spread

Staging Criteria

The American Joint Committee on Cancer (AJCC) developed the TNM classification system for staging. This system details the key components of a patient’s stage. The tables below outline the components of the staging system and how they relate to the number system of I through IV.

TNM Staging Classifications

T Size and Depth of theTumor in the Colorectal Wall	N Lymph Nodes Carrying Cancer Cells	M Spread (Metastases) to Distant Organs
Tis: Tumor has not grown beyond the inner layer of the colon or rectum (earliest stage)	N0: None	M0: None
T1: Tumor has invaded the muscular layer of the colon or rectum	N1: 1 to 3 lymph nodes N1a: 1 node N1b: 2-3 nodes	M1: Yes (typically the lung or liver) M1a: 1organ/site M1b: >1 organ/site
T2: Tumor grew into the colorectal wall	N2: 4 or more lymph nodes N2a: 4-6 N2b: >7 nodes
T3: Tumor grew to the surface of the colorectal wall but not into neighboring tissue or organs
T4a: Tumor grew through the colorectal wall T4b: Tumor grew through the colorectal wall and into nearby tissues or organs

These factors combine to determine the stage. Following the chart below, for example, a stage II colon cancer would be one that has grown into the colorectal tissue, but it has not spread to nearby lymph nodes and shows no sign of spread to distant organs. If the same patient had cancer cells in the lymph nodes, the cancer would be classified as stage III. In its most detailed form, some stages also have lettered subgroupings that you may encounter, so we outlined them below as well.

Breakdown of Colorectal Cancer Stages

Stage	TMN Criteria			Description
0	Tis	N0	M0	The tumor is still within the inner layer of the colon or rectum. This is also called carcinoma in situ or intramucosal carcinoma. (Also known as Duke A stage.)
I	T1 or T2	N0	M0	The tumor is confined within several layers of the colorectal wall and has not spread to nearby tissue or organs. After surgery to remove the tumor, no further treatment is typically provided. (Also known as Duke B stage.)
II				There is no lymph node involvement or spread to distant organs. (Also known as Duke C stage.)
IIA	T3	N0	M0	The tumor has grown to the colorectal wall but not into neighboring tissues or organs. After surgery to remove the tumor, no further treatment is typically provided.
IIB	T4a	N0	M0	The tumor has grown through the colorectal wall. Many of these patients receive further treatment.
IIC	T4b	N0	M0	The tumor has grown through the colorectal wall and into neighboring tissues or organs. Many of these patients receive further treatment.
III				Cancer cells have been detected in the lymph nodes, but the cancer has not spread to distant organs. Chemotherapy typically follows surgery. (Also known as Duke D stage.)
IIIA	T1 or T2 T1	N1 N2a	M0	The tumor is confined to the colorectal wall. Cancer cells have been detected in up to 6 lymph nodes, but the cancer has not spread to distant organs.
IIIB	T3 or T4a T2 or T3 T1 or T2	N1 N2a N2b	M0	The state of the tumor can vary (T1 through T4). Cancer cells were detected in the regional lymph nodes.
IIIC	T4a T3 or T4a T4b	N2a N2b N1 or N2	M0	The tumor has reached or penetrated the colorectal wall, potentially into other tissue or organs (T4). Cancer cells were detected in regional lymph nodes.
IV	Any T	Any N	M1	The cancer has spread to distant organs. The tumor and lymph node status can vary. Treatment options typically include chemotherapy or radiation. (Also known as Duke E stage.)

Role of Lymph Nodes in Staging

The lymphatic system acts as a filter to prevent foreign bodies from entering your bloodstream. Through a series of lymph nodes located near vital organs, this system traps bacteria and exposes it to immune cells for destruction to prevent infection. Each lymph node is a small, bean-shaped mass, and you may have more or less of these in your body at any given time depending on the immune system activity.

Based on this filtering role, lymph nodes serve as a first point of detection to determine whether cancer cells have left the original tumor site. In the case of colorectal cancer, at the time of surgery, the tumor and surrounding lymph nodes are removed for examination.

Imperfections of Current Lymph Node Analysis Method

The current standard practice is for the hospital pathologist to microscopically examine one or more thin sections of each lymph node for evidence of cancer. This generally involves a 5 µm section of each lymph node, which amounts to less than 1% of the lymph node being sampled for the spread of cancer. This small sample size, therefore, means a lymph node could be deemed cancer free while cells reside in the remaining 99% of the node tissue.

Breakthroughs in Detecting Colorectal Cancer Spread

While microscopic examination can serve as an initial test, its imperfections may be contributing to the up to 20% of stage I and II patients who are deemed cured (no cancer cells in the lymph nodes) yet experience a recurrence of their cancer later. Fortunately, breakthroughs in genetic testing are opening options to test the lymph nodes with much greater sensitivity.

With the Previstage™ GCC Colorectal Cancer Staging Test, 50% or more of each lymph node is examined using a molecular testing technique. Whereas traditional microscopic examination can detect one cancer cell in 200 normal cells, molecular testing can detect one cancer cell in 10 million normal cells. That’s a 100,000x improvement in sensitivity across a much larger sample of your lymph node, thus significantly increasing the chance of detecting any cancer cells that have spread from the tumor and providing more accurate information for making critical treatment decisions.