Immunotherapy may help shrink a tumor or slow the growth of cancer cells. People may have it in combination with other treatments for stomach cancer.

Immunotherapy is a treatment that helps the immune system better identify and destroy cancer cells. People may have immunotherapy alongside other treatments for advanced stomach cancer.

This article explores immunotherapy for stomach cancer, which drugs it may involve, its effectiveness, possible side effects and how to manage them, and support for stomach cancer.

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According to the American Cancer Society (ACS), a person may receive immunotherapy for advanced stages of stomach cancer.

If people have metastatic stomach cancer, doctors may use immunotherapy to control the growth of the cancer and prevent or ease any problems the disease is causing.

Immunotherapy may also be an option if surgery is unable to remove the cancer completely.

People may have immunotherapy alongside other treatments, such as chemotherapy or targeted drugs. These treatments aim to shrink the cancer to make surgery possible or to control the cancer and its effects.

The type of treatment a person has depends on whether cancer cells test positive for certain proteins, such as the PD-L1 protein.

Immune checkpoint inhibitors are a type of immunotherapy drug for stomach cancer.

The immune system has immune checkpoints, which are proteins on immune cells, or T-cells.

These checkpoints help prevent the immune system from attacking healthy cells and turn on or off to make an immune response. If the checkpoints turn off, it can prevent the immune system from finding and destroying cancer cells.

Immune checkpoint inhibitors prevent the checkpoints from turning off, which means they can destroy cancer cells.

Different immune checkpoint inhibitors work against different checkpoint proteins, including:

  • CTLA-4
  • PD-1
  • PD-L1

PD-1 inhibitors

PD-1 inhibitors, including nivolumab (Opdivo) and pembrolizumab (Keytruda), target the PD-1 protein. PD-1 inhibitors may help slow cancer growth and shrink tumors.

People with advanced stomach cancer may have nivolumab, usually alongside chemotherapy. A doctor administers nivolumab as an intravenous (IV) infusion into the veins once every 2 to 3 weeks.

Pembrolizumab is a first-line treatment for advanced stomach cancer. If cells test negative for the HER2 protein, people may also have chemotherapy.

If cancer cells are HER2-positive and also test positive for PD-L1 protein, people may have pembrolizumab alongside chemotherapy and trastuzumab (Herceptin), a targeted drug.

Pembrolizumab is also suitable if cancer cells test positive for certain genetic features, including:

  • a high level of microsatellite instability (MSI-H)
  • an abnormality in a mismatch repair gene (dMMR)
  • high tumor mutational burden (TMB-H)

People may have pembrolizumab as an IV infusion once every 3 to 6 weeks.

A large-scale clinical trial suggests that combined treatment with nivolumab and chemotherapy may significantly improve overall survival compared to chemotherapy alone in people with advanced stomach cancer.

Another large-scale clinical trial also found pembrolizumab, in combination with chemotherapy, significantly improved overall survival compared to a placebo with chemotherapy in those with advanced stomach cancer.

Side effects of immunotherapy for stomach cancer may include:

In some cases, immunotherapy may have more severe side effects, such as a reaction to the IV drug infusion. This is similar to an allergic reaction and can cause dizziness, difficulty breathing, rash, fever, and chills.

A person may also experience an autoimmune reaction, in which the immune system mistakenly attacks healthy parts of the body and can cause severe problems with organs.

The ACS offers advice for managing various side effects that people may experience with immunotherapy.

For example, to mitigate fatigue and weakness, a doctor may recommend:

  • nutritional therapy
  • counseling
  • sleep therapy
  • exercise
  • yoga
  • massage therapy

To manage nausea and appetite loss, a person can try:

  • eating smaller meals
  • eating their favorite foods at any time of the day
  • consuming snacks that are high in calories and protein
  • taking part in physical activity

Medications can also help people manage side effects. A doctor may alter the dosage or stop immunotherapy if the side effects are severe.

A doctor may give people corticosteroids if an overreaction of the immune system is causing side effects.

People can contact a doctor if they experience new symptoms or side effects while undergoing immunotherapy.

It is important to inform a doctor immediately if people have severe reactions to medication, such as dizziness, wheezing, fever and chills, or difficulty breathing.

Doctors can help people manage minor side effects of medication, or they recommend stopping treatment for severe side effects.

Many organizations and support groups can offer guidance and support to people with stomach cancer. People may find the following helpful:

Immunotherapy may be part of the treatment for advanced stomach cancer or cancer that is untreatable with surgery. People may have it alongside chemotherapy or sometimes targeted therapy.

Immunotherapy for stomach cancer includes immune checkpoint inhibitors. These drugs may be most effective in combination with chemotherapy.