what does stage 3 colon cancer mean?

Colorectal cancer stages

Making an educated treatment decision begins with the stage, or progression, of the disease. The stage of colorectal cancer is one of the most important factors in evaluating treatment options.

Stage III colorectal cancer

Stage III colorectal cancer is further divided into three more separate categories: IIIA, IIIB and IIIC. The difference between the categories lies in the extent to which the cancer has spread, and how many lymph nodes have been affected.

• Stage IIIA: The cancer has grown into the submucosa. It may have also grown into the muscularis propria. The cancer has spread to 1 – 3 lymph nodes near the site of the primary tumor, but has not spread to distant sites.


• Stage IIIB: The cancer has grown into the outermost layer of the colon or rectum, but has not reached nearby organs. Or, it has grown through the wall of the colon or rectum and into nearby organs or tissues. The cancer has spread to 1 – 3 lymph nodes near the primary site, but has not spread to distant organs.


• Stage IIIC: The cancer may or may not have grown through the wall of the colon or rectum, but has spread to four or more lymph nodes near the primary site. The cancer has not metastasized to distant sites.

Stage IIIA colorectal cancer can be staged in two different ways using the TNM scale:

• T1- T2: If the cancer has grown into the submucosa it is considered T1. Cancer that has grown into the muscularis propria is categorized as T2.


• N1a- N1b: The cancer has spread to 1 – 3 nearby lymph nodes. N1a indicates 1 lymph node, while N1b indicates 2 – 3.


• M0: The cancer has not spread to distant organs.


• OR

• T1: The cancer has grown into the submucosa.


• N2a: The cancer spread to 4 – 6 nearby lymph nodes.


• M0: The cancer has not spread to distant organs.

Stage IIIB can be represented in three different ways using the TNM scale:

• T3-T4a: The cancer has grown through the muscularis propria and into the outermost layers of the colon or rectum, but not all the way through them (T3). Or, the cancer has grown through the visceral peritoneum, the outermost lining of the intestines (T4a).


• N1a- N1b: The cancer has spread to 1 – 3 nearby lymph nodes. N1a indicates 1 lymph node, while N1b indicates 2 – 3.


• M0: The cancer has not spread to distant organs.

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