Colon Cancer: NCCN Guidelines for Patients
The NCCN Guidelines for Patients were developed by the National Comprehensive Cancer Network (NCCN). NCCN is an organization that unites leading cancer care centers in the United States of America. Its activities are focused on scientific research, treatment and education of patients.
Colon cancer basics
Colon cancer is a common and highly treatable cancer. Advances in screening and treatment have led to better outcomes for patients. This chapter provides some basic information about colon cancer that will help prepare you for treatment.
The colon
The colon is the longest part of the large intestine, also known as the large bowel. The large bowel is a long tube-shaped organ that forms the last part of the digestive system. The digestive system breaks down food for the body to use.
After being swallowed, food passes through the esophagus and into the stomach, where it is turned into a liquid. From the stomach, food enters the small intestine. Here food is broken down into very small parts to allow nutrients to be absorbed into the bloodstream. Partly digested food then moves into the colon.
The colon is the first and longest section of the large bowel. It is almost 5 feet long and has four parts: the ascending, transverse, descending, and sigmoid colon.
The first part of the colon is called the cecum. This pouch is about the size of a small orange. Sticking out from the cecum is a skinny tube called the appendix. It is closed at one end, and is about the size of a finger. In the colon, water is absorbed from unused food, changing it from a liquid to a solid. This solid, unused food is called feces or stool. Stool then moves into the last section of the large bowel, called the rectum. Stool is held in the rectum until it exits the body through an opening called the anus.
Colon polyps
A polyp is an overgrowth of cells on the inner lining of the colon wall. There are different types of polyps. Some types are more likely to turn into cancer than others. The most common type is called an adenoma.
Adenomas are considered pre-cancerous. While it may take many years, adenomas can become invasive colon cancer. Cancer that forms in an adenoma is known as an adenocarcinoma.
Adenocarcinoma is the most common type of colon cancer. Polyps that rarely turn into cancer include hyperplastic and inflammatory polyps. Removing polyps can prevent cancer before it starts. Polyps can also be tested to make sure that cancer has not already started to develop. While most polyps do not become cancer, almost all colon cancers start in a polyp. Most polyps can be removed during a colonoscopy using a minor surgical procedure called a polypectomy.
More information on colon polyps is provided in Part 4: Non-metastatic cancer.
Staging
The cancer stage describes the extent of cancer in the body. It is used to plan which tests may be needed and which treatments are best for you. Having a general idea of the structure of the colon wall is helpful for understanding how colon cancer is staged.
The colon wall is made of layers of tissue. Cancer starts in the innermost layer that comes in contact with food. This layer is called the mucosa. The next layer is the submucosa. It is made of connective tissue and contains mucus glands, blood and lymph vessels, and nerves. The submucosa is followed by a layer of muscle called the muscularis propria. The outer, fourth layer is called serosa (or adventitia).
If left untreated, cancer cells grow through the layers of the colon wall, towards the inside of the abdomen. The cancer can then invade structures or organs outside of the colon. Cancer cells can also break off from the colon tumor and travel through lymph or blood to nearby lymph nodes.
The American Joint Committee on Cancer (AJCC) tumor, node, metastasis (TNM) system is used to stage colon cancer. In the AJCC system, the following key pieces of information about the cancer are used to give it a stage:
- T: How far the tumor has grown into or through the colon wall
- N: Whether any lymph nodes have cancer
- M: Whether the cancer has spread to areas or organs outside the colon (metastasized)
The T, N, and M scores are combined to assign the cancer a stage. There are 5 stages of colon cancer. They are numbered 0, I (1), II (2), III (3), or IV (4). The stages are explained below.
Stage 0
There are abnormal cells on the innermost layer of the colon wall. These abnormal cells may become cancer and spread into deeper layers of the colon wall. Stage 0 colon cancer is also called carcinoma in situ of the colon.
Stage I
The cancer has grown into either the second or third layer of the colon wall. There is no cancer in nearby lymph nodes or in areas outside the colon.
Stage II
The cancer has grown into, or beyond, the fourth layer of the colon wall. There is no cancer in nearby lymph nodes or in areas outside the colon.
Stage III
The cancer has spread from the colon to nearby lymph nodes or there are tumor deposits. Tumor deposits are small tumors in the fat around the colon.
Stage IV
The cancer has spread to areas outside the colon and nearby lymph nodes. Colon cancer spreads most often to the liver and/or lungs.
Key points
- The colon is the first and longest part of the large bowel.
- The colon has four parts: the ascending, transverse, descending, and sigmoid colon.
- Most colon cancers start in polyps called adenomas.
- If left untreated, cancer grows through the colon wall towards the inside of the abdomen.
- Cancer cells can spread to other body parts through lymph or blood. This is called metastasis.
- The stage is an assessment of the extent of cancer in the body.
You can read more about Colon Cancer, its treatment methods and follow-up after treatment in the full text of the recommendations for patients by downloading it below.