What is cancer immunotherapy and how effective is it?

For decades, the most effective cancer treatments have involved surgery and cycles of chemotherapy or radiation therapy. But some of these treatments can harm healthy cells, which is why advancements that harness the power of the immune system are important.

“Some patients have really remarkable responses to immunotherapy that last for years – in some cases so many years that we think these patients can even be cured of their disease,” says Ezra Cohen, MD, Co-Director of Precision Immunotherapy Clinic at UC San Diego Health. This therapy doesn’t work for all cancers yet, but here’s the last one:

What is immunotherapy and how does it work?

Normally, the immune system attacks anything foreign to the body, such as viruses and bacteria. But because cancer starts in non-cancerous cells, the immune system doesn’t always see it as dangerous.

“The goal of immunotherapy is to teach the immune system to recognize and kill cancer cells,” says Aung Naing, MD, professor of experimental cancer therapy at the University of Texas MD Anderson Cancer Center in Houston.

The most common type of immunotherapy for cancer involves checkpoint inhibitors, drugs that slow down an immune response already underway, unleashing its full power. With chimeric antigen receptor (CAR) T cell therapy, doctors take T cells from a patient’s blood, make them to target the tumor, and deliver them to the patient to attack the cancer.

Scientists are also developing vaccines, not only vaccines that prevent cancer, such as the HPV vaccine, but also vaccines that stimulate the immune response. And to intensify the attack on cancer, they create monoclonal antibodies, versions of the body’s own anti-disease antibodies, in the lab.

What types of cancer does immunotherapy treat?

So far, patients with several hard-to-treat cancers (including melanoma, head and neck cancers, and kidney, bladder, and non-small cell lung cancer) have most benefited from immunotherapy. “These types of tumors are considered ‘hot’ because the immune cells they contain can be activated,” says Dr. Naing. “They respond well to immunotherapy.”

Other types of cancer, such as colon and pancreatic cancer and most breast cancers, are considered severely immunosuppressive or “cold,” but researchers are starting to see success by combining immunotherapy with traditional treatments.

The FDA recently approved the first immunotherapy for breast cancer after a checkpoint inhibitor (called atezolizumab) combined with chemotherapy was found to have significant effects. It is now a first-line treatment for some women with breast cancer tumors that are triple-negative – an aggressive and particularly deadly form of the disease. A monoclonal antibody called pembrolizumab has also been approved with chemotherapy for certain types of early stage triple negative breast cancer.

How effective is immunotherapy?

Researchers are trying to understand why immunotherapy agents only work for about 20% of cancer patients and why some patients experience life-threatening complications while others have virtually no side effects.

Meanwhile, the race to develop more treatments continues. “Immunotherapies were approved for 20 different cancers at last count,” says Dr. Cohen. “This marks a new era in cancer treatment.”

This article originally appeared in the February 2021 issue of Prevention.

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