What Are the Signs That Immunotherapy Is Working?

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?

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 provider 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.

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.

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, as of right now, there aren’t any blood tests that are FDA approved or authorized to measure how well immunotherapy is working. 

More on this next. 

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 (NSCLC) to immunotherapy.

Another study is investigating whether a type of liquid biopsy (ctDNA) can detect a response to immunotherapy faster than other imaging tools. Other 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:

• 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.

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. But by comparison, people usually experience a delayed response to immunotherapy. It doesn’t usually work as fast as chemotherapy. 

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 that don’t respond well to traditional cancer treatments.

Yet, there are many immunotherapy medications. 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's 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 hasn’t been well 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, please 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

• Diarrhea

• Fast or irregular heartbeat

• Retaining water (e.g., swelling, weight gain)

• Higher risk of infection

• Nasal congestion

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.

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Written by:

Nikki Javit, PharmD

Nikki Javit, PharmD, is a clinical pharmacist with certifications in international travel medicine, immunization delivery, and pharmacogenomics. She received her bachelor’s of science in biology from Indiana University Bloomington and her doctor of pharmacy degree from Butler University.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

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