The short answer
Interval Growth is report language. In plain English, it means a finding is larger than it was on a prior scan. The phrase needs the rest of the report, your symptoms, prior scans, and your cancer history to know what happens next.
Interval Growth is a report description, not the whole diagnosis.
a finding is larger than it was on a prior scan
Growth can matter, but the amount, timing, and type of finding guide concern.
The impression and recommended follow-up are usually the most practical parts of the report.
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The full explanation.
What "interval" means on a scan report
The "interval" is simply the time between two scans. Interval growth means a finding is larger on your current scan than it was on a prior one. This word only makes sense in comparison. A single scan cannot show interval growth on its own. It takes at least two scans, compared side by side, to say whether something has changed.
Why comparison matters more than a single snapshot
A single scan is a snapshot in time. It can describe a spot's size, shape, and appearance. It cannot describe its behavior. Behavior only shows up over time. This is why radiologists actively seek out prior imaging to compare against. Your report often specifically states whether prior scans were available for comparison. A finding read without any comparison carries more uncertainty than the same finding read alongside an older scan.
How doctors decide whether growth counts
For research and many treatment decisions, doctors use a formal standard called RECIST. It defines what counts as meaningful growth, not just any measurable difference. Under this standard, the added-up diameters of the lesions being tracked generally need to rise by at least 20%. That total also has to rise by at least 5 millimeters in absolute terms. Only then is it called progressive disease, rather than normal measurement variation. This threshold exists for a reason. Measuring the same lesion twice, even with no real change, can produce slightly different numbers, just from how the images are read. A small difference between two measurements is not automatically real growth. A difference that clears both thresholds is taken seriously, though.
What interval growth suggests, and what it does not
Interval growth in a known cancer often suggests something specific. The current treatment may not be fully controlling it. Or a monitored area has progressed and needs a change in plan. Interval growth in a previously unclear or "probably benign" finding raises its priority. A spot that looked low-risk before, but has grown since, is usually reclassified and often biopsied. That said, interval growth alone does not always mean cancer or cancer progression. Some benign conditions grow slowly too. Measurement differences between different scanners or techniques can occasionally create the appearance of growth where none really occurred.
Why the flip side matters too
The absence of interval growth is also meaningful. It is often the more common finding, too. A spot that has stayed the same size over a year or more is one of the more reassuring patterns in monitoring. This is a major reason follow-up scans, done on schedule, matter as much as the original finding itself.
What to ask your team
- How does this compare to my prior scan, and by how much did it change?
- Does this amount of growth meet a threshold your team considers meaningful, or could it be measurement variation?
- Does this finding change my treatment plan?
- When is my next follow-up scan, and what would prompt an earlier one?
Sources
Words to know
Tap any term to see what it means.
Common questions
Does "interval growth" mean cancer?
Not by itself. It means a finding is larger than it was on a prior scan. The rest of the report and your clinical context determine how concerning it is.
Why does this phrase appear on my report?
Interval Growth appears when a radiologist compares current and old imaging. Radiologists and pathologists use precise phrases so your care team knows what was seen.
What should I ask next?
Ask whether the finding is benign-appearing, indeterminate, or suspicious, whether old reports were compared, and what follow-up is recommended.
Questions to ask your doctor
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Your next step
Look up more plain-language explanations for report wording.
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Sources last checked: 2026-07-21 what this meansLast updated: 2026-08-17Next planned review: 2027-07-21
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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: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
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.
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