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For decades, the most effective treatments for cancer have involved surgery and rounds of chemotherapy or radiation. But some of these treatments can harm healthy cells, which is why advances that control the power of the immune system are big business.
“Some patients have truly 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 the Precision Immunotherapy Clinic at UC San Diego Health. This therapy still doesn’t work for all types of cancer, but here’s the latest 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 investigative 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 draw an immune response that is already underway, releasing all of its power. With chimeric antigen (CAR) T cell therapy, doctors remove T cells from the patient’s blood, design them to target the tumor and return them to the patient to attack the cancer.
Scientists are also developing vaccines – not just those that prevent cancer, like the HPV vaccine, but also those that boost the immune response. And to increase the attack on cancer, they are creating monoclonal antibodies, versions of the body’s antibodies that fight disease, in the laboratory.
What types of cancer does immunotherapy treat?
So far, it is patients with several types of cancer that are difficult to treat (including melanoma, head and neck cancer and kidney, bladder and non-small cell lung cancer) that have benefited most from immunotherapy. “These types of tumors are considered ‘hot’ because the immune cells in them 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 to be severely immunosuppressive or “colds”, but researchers are beginning to see success combining immunotherapy with traditional treatments.
The FDA recently approved the first immunotherapy for breast cancer after a checkpoint inhibitor (called atezolizumab) combined with chemotherapy has been shown to have significant effects. It is now a first-line treatment for some women with triple-negative breast cancer – an aggressive and particularly deadly form of the disease. A monoclonal antibody called pembrolizumab has also been approved along with chemotherapy for certain types of early triple-negative breast cancer.
How effective is immunotherapy?
Researchers are trying to understand why immunotherapeutic agents work only for about 20% of cancer patients and why some patients have life-threatening complications, while others have almost no side effects.
In the meantime, the race to develop more treatments continues. “Immunotherapies were approved for 20 different types of cancer at the last count,” says Dr. Cohen. “This is signaling a new era of cancer therapy.”
This article originally appeared in the February 2021 issue of Prevention.
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