Colorectal cancer is cancer of the colon (large intestine) and rectum. This type of cancer usually starts as polyps, which are noncancerous masses of cells that can become cancer.
Stages of colorectal cancer, which range from 0 to 4, refer to how far the cancer has spread away from the original growth. It takes into account whether the cancer has spread into the colon walls, to nearby lymph nodes, or to distant organs.
Stage 4 colorectal cancer is divided into three types:
- 4A: The cancer may or may not have spread through the colon wall or lymph nodes, but has spread to one distant area or organ.
- 4B: The cancer may or may not have spread through the colon wall or lymph nodes, but has spread to more than one distant area or organ.
- 4C: The cancer may or may not have spread through the colon wall or lymph nodes, but has spread to distant parts of the abdominal cavity wall, known as the peritoneum.
According to the American Society of Colon and Rectal Surgeons (ASCR), approximately 63 percent of people with colorectal cancer are diagnosed only after the cancer has spread beyond the colorectal walls or to distant organs.
In early stages, colorectal cancer may not cause any symptoms. However, when it does cause symptoms, they are similar across stages. Common symptoms include:
- blood (dark red or bright red) in your stool
- unexplained weight loss
- fatigue and weakness
- changes in your bowel movements, such as constipation or diarrhea, for four weeks or more
- cramping or stomach pain
- a feeling that you need to have a bowel movement, even after you have one
Colorectal cancer can cause bowel obstructions at any stage, but especially stage 4. Symptoms of a bowel obstruction include:
- severe abdominal pain
- nausea or vomiting
- inability to pass gas or stool
- loss of appetite
Stage 4 colorectal cancer may also cause symptoms in the place the cancer spread to. For example, you may have shortness of breath if the cancer has spread to your lungs.
Treatment for stage 4 colorectal cancer depends on how many places the cancer has spread, where the cancer has spread, and other factors such as your overall health.
Surgery may be possible if the cancer has spread to only a few small areas where it can be removed, such as the liver or lungs. Surgery may help treat the cancer or relieve associated symptoms.
The most common surgical procedure involves removal of the tumors in distant organs, the cancer in the colon or rectum, and nearby lymph nodes.
If you have surgery, you will most likely also have chemotherapy before surgery, to shrink tumors, or after, to ensure that all the cancer is removed.
Chemotherapy is the main treatment for stage 4 colorectal cancer when surgery isn’t possible. However, even with chemotherapy, you might still need colon surgery or a stent (a hollow mesh tube) placed if a tumor is blocking your colon.
Several types of targeted therapies are available for stage 4 colorectal cancer. These may be given with chemotherapy or if other treatments don’t work. Types of targeted therapies include:
- Drugs that stop tumors from forming new blood vessels. These work by blocking a protein called vascular endothelial growth factor.
- Drugs that target a protein called epidermal growth factor receptor, which helps cancer cells grow. This type of targeted treatment can’t be used in cancers with certain mutations, so your doctor will test you for those before started targeted therapy.
- Kinase inhibitors. Drugs to target proteins that help cancer cells grow or proteins that help tumors form new blood vessels.
Immunotherapy may also be considered if chemotherapy doesn’t work.
Radiation therapy isn’t usually used to cure stage 4 colorectal cancer. However, it may be used to shrink tumors and relieve symptoms in conjunction with other treatments.
The five-year survival rate for stage 4 colorectal cancer is approximately 14 percent. However, this rate can go up if the tumors in distant organs are small or can be removed with surgery.
Five-year survival rates are estimated rates for groups. This means that individual survival rates might be different, depending on factors such as treatment response and overall health.
In addition, medical advances may be made for colorectal cancer, so the rates change over time.
Colorectal cancer often isn’t diagnosed until later stages.
Although survival rates decrease for stage 4 colorectal cancer, there are still treatments available, including chemotherapy, targeted treatments, and occasionally surgery.