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How do I know if immunotherapy is working?

Medically reviewed by Sally Chao, MD. Last updated on Aug 22, 2023.

Official answer


Immunotherapy treatment is a novel method of managing several types of cancer. It works by boosting your immune system to better target cancer cells. However, it does not work for every patient.

To see if immunotherapy is effective, your physician (an oncology health provider) must be involved. He or she may order blood tests to check for tumor markers, and he or she may also order scans of the tumor periodically to keep track of it.

What are the signs that immunotherapy is working?

Immunotherapy is deemed effective when a tumor shrinks in size or at least stops growing. It is important to note that immunotherapy drugs may take longer to shrink tumors compared to traditional treatments like chemotherapy.

Rarely, the tumor(s) may seem to enlarge on scans before getting smaller. This illusory enlargement is called pseudoprogression. It does not mean the immunotherapy treatment is not working. Rather, the immune cells penetrating and attacking the tumor make it look bigger. In a case when this happens, your care team may recommend waiting for 2 or 3 more treatment cycles (about 2 months each) to get a confirmatory scan.

Side effects such as inflammation can also confirm that immunotherapy treatment is impacting your immune system in one way or the other. In certain cancers, specific side effects point to the likelihood of treatment success. For example, melanoma patients who develop vitiligo (white patches of blotchy skin) are more likely to have success with their immunotherapy treatment.

Research is ongoing to see if there are ways to determine whether immunotherapy is working much earlier during treatment, or if certain aspects of the tumor make it more likely to respond to immunotherapy. This way, patients who may not benefit don't have to experience side effects for long. They also will not have to delay trying other available therapies.

How long does it take for immunotherapy to work?

Immunotherapy medications can take a while to work. The time for the tumor to start responding and the sort of response will vary from person to person.

  • Some patients may experience pseudoprogression.
  • Certain patients may experience a delayed response to immunotherapy treatment.
  • Other patients may initially start to feel better, followed by a relapse as the cancer develops resistance to the immunotherapy treatment.

For all these reasons, it can take about 2 months after initiating treatment to see a measurable response to immunotherapy.

Related Questions

Can immunotherapy stop working or not work at all?

Unfortunately, immunotherapy does not work for everyone. If a patient is not feeling better and the scan shows a larger tumor and/or new lesions, immunotherapy treatment is probably not working. Your doctor may recommend other ways to treat the cancer. These include:

  • Surgery: a procedure in which a doctor removes cancer from your body.
  • Chemotherapy: uses drugs to stop or hinder the growth of cancer cells.
  • Hormone therapy: prevents the growth of hormone-fueled cancer.
  • Hyperthermia: uses heat to kill cancer cells while preserving normal tissue.
  • Photodynamic therapy: uses a drug that is activated by light to kill cancer cells.
  • Radiation: uses high doses of radiation to kill cancer cells and shrink tumors by damaging their DNA.
  • Targeted therapy: uses drugs that specifically aim for the proteins that control how cancer cells multiply and metastasize.

Your doctor may also suggest taking part in a clinical trial. Trials may provide access to newer immunotherapy treatments and other options that are still being researched.

  1. Larimer BM, Wehrenberg-Klee E, Dubois F, et al, Granzyme B PET Imaging as a Predictive Biomarker of Immunotherapy Response. Cancer Research. May 1, 2017 (77) (9) 2318-2327.doi:1158/0008-5472.CAN-16-3346.
  2. Mullen MM, Mutch DG. Endometrial Tumor Immune Response: Predictive Biomarker of Response to Immunotherapy. Clin Cancer Res. April 15 2019 (25) (8) 2366-2368. doi: 1158/1078-0432.CCR-18-4122.
  3. Cancer Research Institute. What Is Cancer Immunotherapy? October 2020. Available at: [Accessed July 28, 2021].
  4. Ventola CL. Cancer Immunotherapy, Part 2: Efficacy, Safety, and Other Clinical Considerations. Pharmacy & Therapeutics. July 2017, 42(7), 452–463.
  5. American Journal of Managed Care (AJMC). The Promise of Cancer Immunotherapy: Why Patient Education Is Critical, Part I. March 29, 2016. Available at: [Accessed July 28, 2021].
  6. National Cancer Institute (NCI). Types of Cancer Treatment. Available at: [Accessed July 28, 2021].

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