Microsatellite instability-high (MSI-high) colon cancer is a type of colon cancer involving a high number of genetic mutations. People with MSI-high colon cancer may respond well to immunotherapy.

MSI-high colon cancer cells have a large number of genetic mutations. Overall, MSI-high colon cancers are fairly uncommon. They typically respond well to immunotherapy medications.

In the United States, approximately 150,000 people receive a colon cancer diagnosis each year. On average, 65% of these people will survive for at least 5 years.

Some cases of colon cancer involve high numbers of genetic mutations in cancer cells. These cases are known as MSI-high colon cancer. Around 15% of all colon cancers fit into the MSI high category. People with MSI-high colon cancer are good candidates for immunotherapy treatment.

This article will explore what MSI-high colon cancer is in greater detail. Keep reading to learn about treatment options, outlook, and more.

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Colon cancer occurs when damaged cells begin to grow and replicate in the colon. In some cases, random genetic mutations lead to the development of colon cancer. In other cases, lifestyle factors or a family history of colon cancer may increase the risk of this disease.

All instances of colon cancer begin in the same area of the body. But there are several different forms of colon cancer. One way to determine the type of colon cancer a person has is through microsatellites.

MSI-high colon cancer

Each cancer cell contains genetic material, or DNA, that tells the cell what to do. Microsatellites are small, repeating pieces of DNA. High microsatellite instability occurs when at least 30% of these DNA pieces contain mutations.

The body’s immune system recognizes MSI-high colon cancer tumors and sends immune cells to the tumors to stop them from spreading.

Due to this, many people with MSI-high cancer respond well to immunotherapy. According to one 2022 review, up to 50% of people with MSI-high colon cancer have a long-term response to this therapy.

MSS colon cancer

As many as 85% of colon cancer cases are microsatellite stable (MSS).

Although they generally have fewer genetic mutations than MSI-high cells, some MSS cells contain more mutations than others. People with MSS colon cancer may still respond to immunotherapy in these cases.

Recent studies have examined combining immunotherapy with targeted treatments for MSS colon cancer. Researchers have found that combined treatments may be more effective than immunotherapy alone.

People in the early stages of MSI-high colon cancer may respond well to immunotherapy drugs. When these drugs enter the body, they bind to certain proteins on the surface of immune cells. This prevents cancer cells from blocking the immune system.

There are many different types of immunotherapy for MSI-high colon cancer. Immunotherapy drug options may include:

  • pembrolizumab
  • nivolumab
  • ipilimumab

The most effective MSI-high colon cancer treatment varies from person to person. In one 2023 study, researchers found that participants with MSI-high colon cancer responded better to immunotherapy than chemotherapy.

Overall, the participants experienced higher survival rates with immunotherapy.

One 2016 review also notes that MSI-high colon cancer may respond to camptothecin. This drug attacks DNA in cancerous cells. Attacking the DNA of these cells can make it harder for them to grow and spread.

People with MSI-high colon cancer should speak with a doctor to learn more about their treatment options.

Colon cancer outlook depends on the person and their cancer stage. According to information from the Surveillance, Epidemiology, and End Results (SEER) database, people with early stage colon cancer have a 91% relative survival rate. This means they are 91% as likely to survive for 5 years as people without the same cancer diagnosis. In the later stages of this disease, the relative survival rate drops to 13%.

People with MSI-high colon cancer have a better outlook than those with other forms of colon cancer. They are also less likely to experience a recurrence of their cancer.

Evidence shows that MSI-high colon cancer tumors rarely spread or metastasize. The high number of DNA mutations in these tumors may play a role. Damaged DNA may not instruct cells to grow and spread as effectively.

Because there is a lesser chance of MSI-high colon cancer spreading, people with this type of colon cancer may have a better outlook. However, as with other forms of colon cancer, it is more difficult to treat once it spreads to other parts of the body.

Of course, MSI-high colon cancer outlook varies from person to person. Factors such as age or overall health can affect a person’s outlook. People with MSI-high colon cancer should consult a doctor to learn more about their unique outlook.

Colon cancer occurs when damaged cells grow and spread throughout the colon. In MSI-high colon cancer, cancerous cells contain a high number of mutations. These mutations trigger the body’s immune system to attack these cells.

As MSI-high colon cancer triggers this immune response, immunotherapy drugs may help treat this disease. Immunotherapy drugs prevent cancer cells from fighting immune cells.

People with MSI-high colon cancer typically have a better outlook than those with other forms of colon cancer. A person with MSI-high colon cancer should speak with a doctor to learn more about their unique outlook and treatment options.