Colorectal cancer is the third most common cancer that affects both men and women in the United States. Understanding the anatomy of the colon can help you better understand the diagnosis of colon cancer. In properly assessing the stage of colon cancer, a more accurate treatment plan can be established with you and your doctor.
The colon and rectum work to reabsorb water, vitamins, potassium, and other secretions. The colon also compacts and moves waste toward the rectum. The colon and rectum are made up of the inner lining called the mucosa, submucosa, smooth muscle, and fibrous outer tissue called subserosa and serosa.
The first steps for getting evaluated for colon cancer include a colonoscopy, bloodwork, and radiographic imaging like computer tomography (CT Scan) to help with tumor staging. Tumor staging provides doctors with a clearer understanding of how advanced a cancer is within a patient's body.
Cancer staging is a system that helps medical providers describe the size of the tumor and if cancer has spread, and it is represented by a system from 1 to 4. The number of the stage depends on whether the cancer has spread, with stage 4 being the point at which cancer has spread to many other areas of the body, otherwise known as metastasis. The American Joint Committee on Cancer’s TNM system provides a standard framework in staging colorectal cancer.
• “T” represents tumor size and depth of invasion into the healthy tissue of the colon or rectum.
• “N” represents any spread to the nearby lymph nodes.
• “M” represents any metastasis or spread to other organs such as the liver or lungs.
A scale of 0 to 4 is applied to each component above to evaluate the cancer stage and help determine the best treatment. Although the tumor staging may guide the treatment options, your treatment plan personalized based on your unique circumstances.
Stage 0 Colon Cancer
At this stage, the tumor is known as carcinoma in situ. It is at its earliest stage since it has not grown beyond the inner layer of the colon or rectum. These abnormal cells are not malignant or cancerous and are referred to as precancerous polyps.
Stage I Colon Cancer
At this stage, cancer cells have grown past the inner lining of the colon and may spread into the submucosa. The cancer cells may have also spread to the muscle layer of the colon or rectum. Yet, at this stage, cancer has not spread to lymph nodes or other organs.
The treatment involves surgery to remove cancer. If the cancer is considered high grade or cancer cells remain around the edges, a partial colectomy—surgery to remove part of the colon with cancer—may be needed, and you may not need any more treatment.
Stage II Colon Cancer
This stage has three subcategories and depends on the extent that cancer cells have invaded the walls of the colon and if they have attached or grown into other nearby organs.
- Cancer has grown into the outermost layer of the colon or rectum. It has not reached nearby organs and has not spread to any lymph nodes or metastasized.
- Cancer has grown through the wall of the colon or rectum but has not yet reached other nearby tissues or organs. It has not spread to nearby lymph nodes or metastasized.
- Cancer has grown past the wall of the colon or rectum and may have extended into nearby organs or tissues. It has not spread to nearby lymph nodes or metastasized.
A partial colectomy, surgery to remove the section of the colon containing cancer cells and any nearby lymph nodes, may be the only treatment needed. Your doctor may also recommend chemotherapy after surgery if your cancer is at higher risk of recurring.
Stage III Colon Cancer
Below are the characteristics of a Stage III colon cancer diagnosis, which range from the location of the cancer to the extent of its spread.
- Cancer has invaded the first two layers of the colon or rectum wall and may have reached the muscular layer. It has also reached 1-3 lymph nodes, or the cancer cells are around the fat surrounding the lymph nodes, but have not metastasized.
- Or cancer cells grew into the first two layers of the colon or rectum and spread to 4-6 lymph nodes but have not metastasized.
- Cancer cells spread to all layers of the colon or rectum wall. They may have spread to the tissue lining the abdominal organs but not yet the nearby organs themselves. Cancer is found in 1-3 lymph nodes without metastasis.
- Or cancer cells spread into the muscle of the colon or rectum or all its layers and have reached 4-6 lymph nodes without metastasis.
- Or cancer cells spread through the first two layers of the colon or rectum or into the muscle layer and are found in seven or more lymph nodes without metastasis.
- Cancer cells invaded all layers of the colon or rectum wall. They may have spread through the tissue and are found in 4-6 lymph nodes without metastasis.
- Cancer cells may have invaded the colon or rectum's smooth muscle and spread to the tissue that lines the organs in the abdomen but not spread to other organs and has reached seven or more lymph nodes without metastasis.
- Or cancer cells invaded through the colon or rectum wall have grown into a nearby organ or tissue, found in at least one lymph node or the fat around the lymph node without metastasis.
Partial colectomy with adjuvant chemotherapy is the standard treatment for stages within Stage III colon cancer. Your doctor may recommend radiation along with chemotherapy if the cancer is more advanced. Your doctor will determine if radiation therapy and or chemotherapy alone will be enough if you cannot undergo surgery.
Stage 4 Colon Cancer
This is the most advanced stage of colon cancer and includes “Any T” and “Any N” since it has spread throughout all walls of the colon and has affected lymph nodes.
- Cancer metastasized to either the liver, lung, ovary, or a lymph node far away from the colon.
- Cancer metastasized to more than one organ that is not near the colon or rectum.
- Cancer has spread throughout different parts of the abdominal wall and has metastasized to other organs.
In this stage, surgery is unlikely to serve as a cure. Chemotherapy may be offered to try to shrink the size of the metastatic tumors. If the tumors shrink, you may undergo surgery to have them removed.
If cancer has spread widely, chemotherapy and targeted therapies will be the mainstay treatment. Finally, for advanced cancers, radiation therapy can also relieve symptoms if the cancer is causing too much pain.