Key takeaways:
Immunotherapy medications help your immune system do a better job at fighting cancer.
Different tests are available that help offer insight into immunotherapy’s effectiveness.
Like other cancer treatments, immunotherapy causes side effects that are different for everyone.
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Your immune system is a critical part of your body's defenses. One of its main jobs is to prevent and fight infections caused by viruses, bacteria, and fungi. Without a functioning immune system, it's possible to develop serious health complications.
Aside from protecting against infections, your immune system can also help fight cancer. But sometimes, it needs help. Many immunotherapy medications have been researched and approved to help your immune system target and fight cancer cells.
Immunotherapy can often help people with cancer live longer compared to traditional treatments like chemotherapy and radiation. But after you start receiving it, you often don't feel noticeably better or different. So, how do you know if these medications are working? Healthcare professionals watch for specific signs. They also account for a response called pseudoprogression, where a tumor can look bigger before it starts to shrink.
Here, we’ll discuss how to tell if immunotherapy is working, its effectiveness, and its potential side effects.
How do you know if immunotherapy is working?
A positive response to immunotherapy is measured by how your cancer improves over time. If it stays the same, gets smaller, or becomes more controlled, that's ideal.
Your healthcare team will be in charge of monitoring this progression. They often use physical exams, imaging tests, and blood tests to measure how a cancer responds to treatment.
Keep in mind that an early scan can be misleading. Sometimes, a tumor looks bigger — or new spots show up — shortly after starting immunotherapy, even though the cancer isn't actually growing. This is called pseudoprogression. It happens when immune cells flood into the tumor, which can make it look larger before it starts to shrink. Because of this, your healthcare team may repeat imaging before deciding whether the treatment is working.
Can blood tests measure immunotherapy progress?
Measuring a tumor's response to immunotherapy can be difficult. Blood tests can help in diagnosing and monitoring some types of cancer, but they don’t always show how well immunotherapy is working. When they do, these types of blood tests usually involve looking for biomarkers. They’re types of natural markers, or signs, that are found in body fluids and tissues throughout the body.
Different blood tests are available that can look for these biomarkers. Some biomarkers are helpful in identifying cancer or when deciding if a certain treatment option may be effective. For example, the FDA has approved a number of blood tests to identify genetic mutations that can predict if people will respond well to immunotherapies.
Separately, it’s thought that some biomarkers could help monitor how well a particular treatment may be working over time. But these are in development. As of right now, there aren’t any blood tests that are FDA approved or authorized to measure how well immunotherapy is working.
Will new blood tests be available in the future?
Most likely. For example, the Cancer Research Institute and the Mark Foundation for Cancer Research are researching a biomarker-directed blood test. This study aims to assess how well a biomarker blood test tracks the response of a type of lung cancer — non-small-cell lung cancer (NSCLC) — to immunotherapy.
Other studies are investigating whether a type of liquid biopsy — circulating tumor DNA (ctDNA) — can detect a response to immunotherapy faster than other imaging tools. Results so far in this field are promising.
How long do you have to be on immunotherapy treatment?
Sadly, there’s not a straightforward answer for this. How long you have to be on immunotherapy depends on several different factors, such as:
The type and severity of your cancer
The type of immunotherapy you're prescribed
How your cancer responds to immunotherapy
If you’re curious how long you might have to take immunotherapy for, talk to your cancer specialist. They may be able to provide more information based on your situation.
How long does it take for immunotherapy to start working?
Immunotherapy treatments usually take longer to show signs of tumor reduction than traditional treatments like chemotherapy and radiation. In practice, your team usually checks for a response with a scan after about 2 to 3 cycles of treatment — roughly 2 to 3 months in.
Chemotherapy works by attacking fast-dividing cancer cells. When people respond to chemotherapy, the treatment starts to work quickly. Immunotherapy helps activate your immune system to better find and destroy cancer cells. By comparison, people usually experience a delayed response to immunotherapy. It doesn’t usually work as fast as chemotherapy.
Because immunotherapy can work slowly, a clear response sometimes takes 6 months or longer, so your team may keep treating you during that window. But there's an upside. Immunotherapy may take more time to start working, but the effects often last longer than traditional treatments.
How effective is immunotherapy?
Immunotherapy is effective for many people who don’t respond well to traditional cancer treatments. But there are many immunotherapy medications, and effectiveness can vary by medication and cancer type.
For example, immune checkpoint inhibitors like pembrolizumab (Keytruda) have long-term benefits for people with melanoma, squamous cell carcinoma (SCC), and Hodgkin lymphoma. CAR T-cell therapy is effective for acute lymphocytic leukemia (ALL) with high remission rates. But, sadly, immunotherapy doesn't work for everyone.
For example, immune checkpoint inhibitors work well for the cancers mentioned above, but very few people with ovarian or pancreatic cancer benefit from these medications. CAR T-cell therapy is still being studied to treat solid tumors, including breast and brain cancers. Use in such cancers hasn’t proven effective yet.
What are some signs that immunotherapy isn’t working?
In general, if you feel worse and tests show your tumor is larger, immunotherapy likely isn't working. If you're concerned about your treatment's effectiveness, speak with your cancer specialist.
What are normal side effects of immunotherapy?
Like with all medications, people can experience side effects from immunotherapy. The side effects you feel will vary depending on your medical history, cancer type, and other medications you’re receiving.
But some side effects are common across most immunotherapy medications. They can occur during and after treatment. Side effects can include:
Flu-like symptoms, such as chills, fever, fatigue, or weakness
Injection-site reactions, like rash, soreness, or swelling
Fast or irregular heartbeat
Retaining water (like swelling or weight gain)
Higher risk of infection
Keep in mind that some immunotherapy medications may carry risks for more serious side effects than others. If you have any bothersome symptoms, let your cancer specialist know as soon as you can.
Frequently asked questions
Immunotherapy can be either curative or palliative, depending on your cancer type, stage, and treatment goals. When a cure is the goal, immunotherapy can sometimes produce long-lasting responses — though it doesn't always work for everyone. When a cure isn't possible, it's often used to shrink the cancer, slow its growth, or ease symptoms. This might help some people live longer or manage their cancer more comfortably. Your healthcare team can tell you which goal applies to your situation.
Yes, you can usually travel while on immunotherapy — as long as your cancer care team gives you the green light. Because immunotherapy can affect your immune system and raise your infection risk, timing matters. So, make sure to ask about the safest windows to travel within your treatment plan.
You’ll also need to take a few precautions along the way:
Get up and move roughly every hour to lower your blood clot risk
Wash your hands often
Avoid crowds
For longer trips, ask your team about arranging care near your destination in case you need it.
Immunotherapy doesn’t stop metastasis, but it can help. Immunotherapy is a systemic treatment. That means it travels through your bloodstream and can reach cancer cells that have spread (metastasized) to other parts of your body. In some people, it shrinks or controls those tumors, sometimes for a long time. But it doesn't work for everyone, and it's not a guaranteed way to stop cancer from spreading. Your healthcare team can estimate how effective immunotherapy is likely to be based on your cancer type.
Immunotherapy can be either curative or palliative, depending on your cancer type, stage, and treatment goals. When a cure is the goal, immunotherapy can sometimes produce long-lasting responses — though it doesn't always work for everyone. When a cure isn't possible, it's often used to shrink the cancer, slow its growth, or ease symptoms. This might help some people live longer or manage their cancer more comfortably. Your healthcare team can tell you which goal applies to your situation.
Yes, you can usually travel while on immunotherapy — as long as your cancer care team gives you the green light. Because immunotherapy can affect your immune system and raise your infection risk, timing matters. So, make sure to ask about the safest windows to travel within your treatment plan.
You’ll also need to take a few precautions along the way:
Get up and move roughly every hour to lower your blood clot risk
Wash your hands often
Avoid crowds
For longer trips, ask your team about arranging care near your destination in case you need it.
Immunotherapy doesn’t stop metastasis, but it can help. Immunotherapy is a systemic treatment. That means it travels through your bloodstream and can reach cancer cells that have spread (metastasized) to other parts of your body. In some people, it shrinks or controls those tumors, sometimes for a long time. But it doesn't work for everyone, and it's not a guaranteed way to stop cancer from spreading. Your healthcare team can estimate how effective immunotherapy is likely to be based on your cancer type.
The bottom line
Immunotherapy is a cancer treatment that offers potential benefits over treatments like chemotherapy and radiation. In some cases, immunotherapy helps people live longer after a cancer diagnosis.
Immunotherapy is effective for many people, but it's important to remember that it doesn't work for all types of cancer. Immunotherapy treatment offers hope in improving how we treat cancer. However, we're still in the early stages of understanding how to use these medications to their full potential.
Why trust our experts?
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