The short answer
A mixed response means some sites shrink while others grow. Teams weigh how you feel, repeat imaging, and on immunotherapy must distinguish this from pseudoprogression before changing course.
A mixed or dissociated response means different sites of the same cancer are behaving differently — some shrinking, some stable, some growing.
Standard response criteria add up the measurements of a few selected lesions, so a mixed picture can be forced into a single label that does not describe what is really happening.
On immunotherapy, dissociated responses have been reported in roughly 3 to 9 percent of patients and are associated with better survival than true progression.
Pseudoprogression — apparent growth caused by immune cells flooding into a tumor — occurs in a small percentage of people on checkpoint inhibitors and resolves on later imaging.
Choose how you want to understand this
The full explanation.
What the phrase describes
A mixed response — often written as a dissociated response — means that different parts of the same cancer are doing different things at the same time. Two liver deposits have shrunk, while a lung nodule has grown. A lymph node has almost disappeared, while a bone lesion looks slightly larger.
This is a real and recognized pattern. It is not a fuzzy reading of the scan. And it is one of the harder results to be handed, because it refuses to be either good news or bad news.
Why one cancer behaves in several ways
Cancer is not one uniform tissue. As it grows and spreads, different deposits pick up different genetic changes. What started as one disease becomes a set of related but distinct populations. A drug may hit a mutation in one deposit and leave another untouched.
The surroundings matter too. Blood supply differs between sites, which changes how much drug arrives. Immune cells reach some places more easily than others. A few sites — the brain in particular — sit behind barriers that many drugs cross poorly. And a site that was irradiated before behaves differently from one that was not.
Why the report may not say mixed response
Formal response criteria were built for clinical trials, where consistency matters more than nuance. Under RECIST 1.1, up to five lesions are chosen as targets. Their longest diameters are added together, and that sum is tracked over time. Partial response means the sum falls by at least 30 percent. Progressive disease means it rises by at least 20 percent, with an absolute increase of at least 5 millimetres, or that a new lesion has appeared.
A genuinely mixed picture gets pulled into whichever category the arithmetic produces. So what your radiologist describes in the body of the report may feel different from the single word in the conclusion. That is why the conversation with your oncologist matters more than the label.
The immunotherapy question that has to be asked first
If you are on a checkpoint inhibitor, apparent growth carries one extra possibility. Immune cells flooding into a tumor can make it physically larger on a scan while the treatment is working. Deposits that were invisible before can become visible for the same reason. This is called pseudoprogression, and it settles down on later imaging.
It is uncommon. Most series report it in roughly 1 to 9 percent of people on checkpoint inhibitors. But missing it is serious, because it means stopping a treatment that was working.
That is why iRECIST exists. Under those rules, imaging that meets progression criteria is recorded as unconfirmed progressive disease. Treatment continues if you are clinically well. A confirming scan is done at four to eight weeks. Progression is only confirmed if the disease has grown further by then.
Dissociated responses on immunotherapy are also uncommon, reported in around 3 to 9 percent of patients. Importantly, they are linked with better survival than genuine progression.
What your team weighs
Several things beyond the images go into the decision.
How you feel is central. New pain, weight loss, breathlessness or a drop in day-to-day function points toward true progression. Feeling well points the other way. Tumor markers, and increasingly ctDNA, add information. Falling levels during apparent growth argue strongly for pseudoprogression. The pattern matters as well. One growing site among many responding ones reads very differently from several growing at once.
The options that follow
Continue and reassess. Most common when you are well, most of the disease is responding, and the growth is small or possibly pseudoprogression.
Treat the growing site locally. Sometimes one site, or a few, progress while the rest stays controlled. That is called oligoprogression. Radiation, surgery or ablation to those sites, while you stay on the same systemic therapy, is a well-established approach. It can stretch the useful life of a treatment considerably.
Biopsy the discordant site. Useful when it might not be cancer at all, or when a resistance mutation would open up a different drug.
Change systemic treatment. Kept for when progression is confirmed, widespread, or comes with symptoms.
A mixed response is one of those situations where the scan alone cannot decide. Ask your team directly which of these paths they are weighing, and what would tip them one way or the other.
Sources
Words to know
Tap any term to see what it means.
Common questions
Is a mixed response good news or bad news?
It is genuinely in between, which is part of why it is hard to sit with. Something is working — the shrinking sites are evidence of that. Something else is not. In immunotherapy studies, people with dissociated responses did better on average than people with straightforward progression. It is not the clean result anyone hoped for, and it is not a failure of treatment either.
Why would parts of the same cancer behave differently?
Because they are not genetically identical. A cancer accumulates changes as it grows and spreads, so different deposits can carry different mutations and respond differently to the same drug. The local environment matters too — how well a site is supplied with blood, how much immune cell traffic reaches it, whether it sits somewhere a drug penetrates poorly, such as the brain.
What is pseudoprogression and how is it told apart from real growth?
On immunotherapy, immune cells can flood into a tumor and make it temporarily larger on a scan, or make previously invisible deposits appear. This resolves on later imaging. It is distinguished mainly by repeating the scan after four to eight weeks while you continue treatment, alongside how you feel clinically. Falling ctDNA or tumor markers during apparent growth also argue against true progression.
Could just one growing spot be treated on its own?
Often yes. When most of the disease is controlled and one or a few sites are progressing — sometimes called oligoprogression — targeting those specific sites with radiation, surgery or ablation while continuing the same systemic treatment is an established approach. Whether it fits your situation depends on how many sites, where they are, and how the rest of the cancer is behaving.
Would a biopsy of the growing lesion help?
Sometimes. It can confirm the growth is cancer rather than inflammation or a second unrelated process, and it can reveal a resistance mutation that opens a different treatment. It is not always necessary, and whether it is worth it depends on whether the result would change what happens next.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Speak With Trained Specialists & Human Navigators
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
Talk to a trained cancer information specialist
Free, confidential assistance from NCI Cancer Information Service via phone, chat, or email.
Contact your oncology team
Locate after-hours contact numbers, portal messages, or urgent triage phone lines.
Find a patient navigator
Get one-on-one help with appointments, logistics, translation, and care coordination.
Find a genetic counselor
Discuss inherited mutation risk, family history, and genetic testing options.
Find an oncology social worker
Access emotional counseling, family support groups, and mental health resources.
Find a financial navigator
Locate copay assistance foundations, grant programs, and lodging/travel support.
Find a clinical-trial specialist
Search matching studies and speak with NCI trial information specialists.
Get urgent help
Immediate emergency guidance for fever (>100.4°F during chemo), severe pain, or shortness of breath.
Help Us Improve This Guide
Did this explanation answer your question and help you determine your next step?
Know someone who needs this?
Plenty of people are looking for something like this and do not know where to start. If this would help a friend or someone you love, send it on — we have written an opening line so you do not have to stare at an empty message. You can change every word of it.
Your message is written and sent in your own email or messaging app — we never see who you send it to, and nothing is added to any list.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Written by: Cancer ExplainedSources last checked: 2026-07-30 what this meansLast updated: 2026-08-10Next planned review: 2027-07-30
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status — Source checked. This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
General education — varies by person. Answers genuinely differ between people. This page explains what commonly varies and points you to your care team for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.
Related articles
- A Symptom Is Not a Diagnosis
- What Symptoms Should I Call My Oncology Team About Today?
- Cancer-Prevention Claims: Evidence, Uncertainty, or Myth?
- How to Read a Cancer Pathology Report
- Stable Disease vs. Partial Response vs. Progression
- What a Variant of Uncertain Significance (VUS) Means
- What Pathologic Complete Response (pCR) Means
- Why PET Scans Show Areas of Uptake (Hypermetabolism)
Still have questions?
Educational answers, plain language
Free to print and share