Colorectal cancer is one of the most common types of cancer, and doctors can often treat it successfully if caught early. However, in some cases the cancer may spread to other tissues and organs, such as the liver, lungs, or brain. This process is called metastasis.

Colorectal cancer refers to cancer that begins in the colon or rectum. Doctors often group these cancers together as they share many features.

Treatment for metastatic colon cancer requires a tailored approach depending on a person’s specific symptoms and progression.

Knowing where metastatic colorectal cancer spreads and the symptoms to be aware of, can help people receive timely treatment and improve their outlook.

Keep reading to find out more about metastatic colorectal cancer, including what it is, where it can spread, and how doctors can potentially treat it.

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Cancers are abnormal growths of tissue that form due to changes in the genetic material of cells. The normal cell cycle can sometimes be disrupted, and can lead to abnormal or rapid replication.

These changes can lead to malignant or benign tumors. Tumors can either be malignant — meaning they can invade surrounding tissues — or benign, meaning they do not spread.

In the case of colorectal cancer, malignant cells form in the lining of the intestine or rectum.

If these cells break off and travel to another part of the body through the lymphatic vessels or blood, they are called metastases. Doctors call this metastatic colorectal cancer.

Learn more about the lymphatic system here.

Doctors divide cancer into stages that describe the progression of cancer. The staging system helps them understand a person’s outlook and the best treatment options. Colorectal cancer has five stages.

The earliest stage is stage 0 — a very early cancer — and then stages 1–4. According to the American Cancer Society (ACS), the lower the number, the less the cancer has spread.

In stage 3 colorectal cancer, the malignant cells have spread to nearby lymph nodes but have not yet spread to other areas. If a person’s colorectal cancer has metastasized beyond the lymph nodes, they are at stage 4.

Metastatic colorectal cancer commonly spreads to the liver. This may be because the liver receives most of its blood supply from the portal vein — a large blood vessel that carries blood from the intestines and spleen. It can also spread to the following areas:

  • lungs
  • brain
  • the lining of the abdominal cavity
  • distant lymph nodes

A person with colorectal cancer might not have any symptoms immediately. However, the following are some potential symptoms people may experience:

  • change in bowel habits, such as diarrhea or constipation
  • weakness
  • fatigue
  • abdominal pain
  • unintended weight loss
  • stools that appear darker or red
  • rectal bleeding with bright red blood
  • blood in the stool

As cancer progresses and spreads, symptoms may depend on where it has metastasized in the body. Examples include:

  • yellow eyes or skin — jaundice — and abdominal swelling if cancer has spread to the liver
  • bone pain and fractures, if cancer has spread to the bone
  • trouble breathing, if cancer has spread to the lungs
  • headaches, dizziness, or seizures if cancer has spread to the brain

However, people should note that other conditions such as infection or irritable bowel syndrome can also cause these symptoms. Therefore, if a person experiences these symptoms, they should contact a healthcare professional for assessment.

A person may discover they have metastatic colorectal cancer when they first receive their diagnosis. Others may find that their cancer has metastasized sometime after their initial cancer diagnosis.

Doctors may need to use various tests to detect and locate metastatic colorectal cancer. Once they have established the presence of cancer, further tests can determine where it has spread.

The primary test to diagnose colorectal cancer is a colonoscopy. If the doctor suspects a person has colorectal cancer, they may collect a tissue sample during the colonoscopy procedure. A laboratory then tests the biopsy tissue sample and examines its specific characteristics to help steer treatment. Doctors then use imaging studies to check if and where the cancer has spread.

Imaging tests that doctors may use include:

  • CT: A CT or CAT scan uses X-rays to create cross-sectional images of a person’s body. It can show if cancer has spread to nearby lymph nodes, or other organs.
  • Ultrasound: Doctors may use this test to see if cancer has spread to the liver. They can also take a biopsy with ultrasound guidance.
  • Magnetic resonance imaging (MRI): Doctors may take a detailed imaging test of the pelvis or abdomen to check for cancer spread in these areas or if lymph nodes are involved.
  • X-ray: Doctors use chest X-rays to check if colon cancer has metastasized to the lungs. They can also show any bone metastases.
  • Positron emission tomography (PET) scan: Doctors may use these scans to look for cancer throughout the body, including the brain. These scans can also help plan treatment and any surgery.

The optimal treatment for a person with metastatic colorectal cancer may depend on where cancer has spread and the location of the tumors. Doctors also consider the person’s general health, age, and potential side effects of any treatment.

People with colorectal cancer may try different treatment options either in combination or one after another. Doctors use the following methods to treat colorectal cancer:

  • Chemotherapy: Doctors may use chemotherapy if surgery would be ineffective. Chemotherapy agents are potent medications that kill cancer cells or prevent them from dividing.
  • Hepatic artery infusion chemotherapy (HAIC): If colorectal cancer has spread to the liver, doctors may use HAIC, a form of regional chemotherapy. It involves delivering chemotherapy drugs into the liver’s hepatic artery. It may destroy malignant cells without damaging healthy liver cells.
  • Radiation therapy: Doctors do not commonly use radiation therapy to treat colon cancer. However, they may use it before surgery to shrink tumors, ease a person’s symptoms, or alongside chemotherapy to help control cancer.
  • Surgery: If cancer has spread widely, surgery may not be an option. However, surgery may be possible if a person has one or two small lesions on the liver.
  • Other systemic therapies: Doctors may also use immunotherapy, biologic therapy, and other targeted therapies.

Additionally, a doctor may discuss clinical trials. These research studies investigate novel treatments that may help a person with metastatic colorectal cancer.

Treatment options for people with this type of cancer have advanced dramatically over the last few decades. However, it is important to note that outcomes can still vary widely across people with advanced disease.

Colorectal cancer is the third most common cancer in the United States, excluding skin cancers.

Metastatic colorectal cancer is late-stage cancer that has spread and is, therefore, more difficult to treat.

The ACS notes that the 5-year relative survival rate for metastatic colon cancer is 14%. Although this may appear a frightening statistic, it does not account for other factors that may affect someone’s outlook, such as variation in treatment success rates. A person’s age and overall health may also affect how they respond to treatment.

Additionally, these statistics describe past cases, and as medicine and treatments advance, survival rates may also improve.

Metastatic colorectal cancer is advanced cancer that has spread to other areas outside the colon and rectum. Commonly, this type of cancer spreads to the lymph nodes and liver, but it may spread to other parts of the body, such as the brain.

Once cancer has metastasized, a person’s chances of a more positive outlook decreases. However, there is a range of treatment options, including chemotherapy. Additionally, new treatments and medical advances may offer people other options.

People should note any symptoms of colorectal cancer, such as changes in bowel movements, blood in the stool, or abdominal pain, and consult a doctor for assessment.

Treatment is more likely to be successful in the earliest stages of cancer.