Immunotherapy vs. Targeted Therapy

Immunotherapy and targeted therapy are both newer kinds of cancer treatment, and they are easy to mix up. The difference is in what they act on:

• Immunotherapy helps your own immune system fight cancer.
• Targeted therapy targets specific proteins that control how cancer cells grow, divide, and spread.

One works through your body's defenses. The other goes after features of the cancer cells themselves.

Your immune system normally finds and destroys abnormal cells. It can slow or prevent the growth of many cancers. But cancer cells find ways to avoid it. Some make proteins that switch immune cells off. Immunotherapy helps the immune system act against the cancer more strongly. Types include immune checkpoint inhibitors, T-cell transfer therapy, monoclonal antibodies, treatment vaccines, and immune system modulators.

Targeted therapy is the foundation of what is called precision medicine. Researchers keep learning more about the DNA changes and proteins that drive cancer. That lets them design drugs to interfere with those proteins. Targeted therapy can stop the signals that tell cancer cells to divide. It can block the growth of new blood vessels a tumor needs. It can also deliver cell-killing substances straight to cancer cells. This differs from chemotherapy, which often kills all cells that grow and divide quickly.

The line between the two is not always sharp. Monoclonal antibodies are lab-made proteins that attach to specific targets on cancer cells, and they are used in both. Some are called immunotherapy because they mark cancer cells so the immune system can find them. Others are called targeted therapy because they directly stop cancer cells from growing, or carry toxins to them. So a single drug can fall into both groups.

For targeted therapy, your tumor usually needs to be tested for a target that a drug can act on. This is called biomarker testing. For some cancers, testing may not be needed. In one form of chronic myelogenous leukemia, for example, nearly everyone with the cancer has the target. Immunotherapy is approved for many cancers, but only some people respond. Researchers are working on ways to predict who will.

Both treatments can cause side effects. Immunotherapy side effects often happen when the revved-up immune system also acts against healthy cells and tissues. Targeted therapy side effects commonly include diarrhea and liver problems. They can also include high blood pressure, fatigue, and skin changes. Most side effects of targeted therapy go away after treatment ends.

Neither treatment is simply "better." They do different jobs. They are sometimes combined with each other, or with chemotherapy and radiation. And not every cancer has a target for them. Ask your care team what is being considered for you, whether testing is needed, and what to expect.