An Overview of Immunotherapy for Colorectal Cancer

Colorectal cancer, which refers to both colon cancer and rectal cancer, occurs in the lining of the colon or rectum. The disease has the ability to metastasize (spread) to other organs and lymph nodes in the body. More than 95 percent of colorectal cancers are adenocarcinomas, a form of tumor that arises in the mucus-secreting glands of the colon or rectum. Recently, researchers discovered that a hereditary disease called Lynch syndrome is a contributor to the development of colorectal cancer. Specifically, Lynch syndrome is responsible for about 5,000 new diagnoses of colorectal cancer in the United States each year.

According to the American Cancer Society, the disease in discussion is the third most common cancer in the United States and the second most fatal. On a global scale, there are roughly 1.8 million new cases of colorectal cancer each year, along with more than 900,000 deaths due to the disease. In 2021, an estimated 104,270 new cases of colon cancer and 45,230 new cases of rectal cancer are expected to occur, along with 52,980 related deaths in the U.S. alone.

Although the overall incidence and death rates among men and women have decreased over the last two decades — mostly because of improved screening tests that detect early-stage cancer. — underutilization of these screening tests mean that a mere 40 percent of colorectal cancers become diagnosed in the early stage, when the prognosis is favorable at 90 percent. Therefore, powerful treatments for colorectal cancer are necessary to prevent the disease from advancing.

Immunotherapy for Colorectal Cancer: Treatment Options

The conventional treatments for colorectal cancer include chemotherapy, radiation, and surgery. Immunotherapy is a class of cancer treatment that takes advantage of a patient’s own immune system to attack and kill cancer cells. The Food and Drug Administration (FDA) has approved many immunotherapy options for colorectal malignancies, including for tumors that are either mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H).

Targeted Antibodies 

Researchers can design antibodies (a protein the immune system uses to identify and neutralize bacteria, viruses, and other foreign objects) that target certain antigens (a substance capable of stimulating an immune response), such as the one found on malignant cells.

Here are some of the immunotherapy medication used to treat colorectal cancer:

  • Bevacizumab (Avastin®). This monoclonal antibody (man-made proteins that function like human antibodies) targets the VEGF pathway and blocks tumor blood vessel growth. The FDA has approved this medication for subsets of patients diagnosed with advanced colorectal cancer, including as a form of first-line therapy.
  • Cetuximab (Erbitux®). This monoclonal antibody can target the EGFR pathway. The FDA has approved this drug for subsets of patients diagnosed with advanced, EGFR-positive colorectal cancer, including as a form of first-line therapy.
  • Panitumumab (Vectibix®). Similar to cetuximab, this monoclonal antibody also targets the EGFR pathway. The FDA has approved this drug for subsets of men and women with advanced, EGFR-positive colorectal cancer.
  • Ramucirumab (Cyramza®). Targeting the VEGF/VEGFR2 pathway and obstructing tumor blood vessel growth, the U.S. FDA has approved this monoclonal antibody for subsets of patients battling advanced colorectal cancer, including as the first line of defense.

Checkpoint Inhibitors

Checkpoint inhibitors target immune checkpoints (key regulators of the human immune system) which, when stimulated, can dampen the immune response to an immunologic stimulus.

  • Ipilimumab (Yervoy®). This checkpoint inhibitor targets the CTLA-4 pathway. The FDA has approved the combination of this medication with nivolumab for subsets of patients with advanced-stage, colorectal cancer that has high microsatellite instability.
  • Nivolumab (Opdivo®). This checkpoint inhibitor targets the PD-1/PD-L1 pathway. The FDA approved this drug for subsets of men and women with advanced colorectal cancer that has high microsatellite instability, including in combination with ipilimumab.
  • Pembrolizumab (Keytruda®). This checkpoint inhibitor targets the PD-1/PD-L1 pathway. The FDA has approved pembrolizumab for subsets of people with advanced colorectal cancer that has high microsatellite instability, DNA mismatch repair deficiency, or high tumor mutational burden, as well as a first-line treatment.

Many other immunotherapies showing promise in treating other forms of cancer are currently in clinical testing for colorectal cancer.

Side Effects of Colorectal Cancer Immunotherapy

Like any form of cancer treatment, immunotherapy can cause some side effects. These include:

  • Fatigue
  • Coughing
  • Nausea
  • Joint pain
  • Decreased appetite
  • Constipation or diarrhea
  • Itching or skin rashes

Other, more serious side effects arise less often. They can include:

  • Infusion reactions. Some patients might experience an infusion reaction while receiving treatment with these drugs. This is quite similar to an allergic reaction and can include flushing of the face, fever and chills, itchy skin, rashes, dizziness, wheezing, and difficulty breathing.
  • Autoimmune reactions. In simple terms, immunotherapy drugs work by removing one of the immune system’s safeguards. Sometimes, the human immune system can react to these drugs by attacking other areas of the body, which could lead to serious and even life-threatening problems in the intestines, liver, kidney, lungs, hormone-making glands, skin, nerves, or other organs.

All patients must tell their doctor or nurse right away if they experience any of these symptoms while getting these drugs. If serious side effects occur, the patient may need to cease treatment and take high doses of corticosteroids (a class of steroid hormones) to suppress their immune system.

Key Benefits of Immunotherapy for Colorectal Cancer

Although chemotherapy and radiation therapy can help improve survival rates, it is imperative to integrate alternative cancer treatments such as immunotherapy to further improve outcomes for patients with advanced colorectal cancer.

Immunotherapy, which causes fewer side effects than conventional methods, involves the use of medication that helps boost the patient’s immune system to effectively locate and destroy cancer cells. This treatment may be implemented when traditional therapies fail to stimulate a tumor to regress, or when surgery cannot successfully remove a tumor. Immunotherapy may also be a treatment option for cancer that returns or metastasizes.

New Hope Unlimited’s Approach to Colorectal Cancer Immunotherapy

Our colorectal cancer care team here at New Hope Unlimited uses a multispecialty approach to treating malignancies. The decision to include immunotherapy into our patients’ treatment plan is the result of decades of collaborative research with cancer treatment pioneers, considering all aspects of the human body’s idiosyncratic circumstances. We choose to offer colorectal cancer patients comprehensive treatments to broaden their options and give them a fighting chance at beating even the most advanced cancer.

For more information about colorectal cancer immunotherapy and how it can benefit you, call us at 480-757-6573 to schedule a consultation.

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