Reading Your Report
What 'Interval Change' and — 'Stable Since Previous Study' Mean
When your scan report uses the words 'interval change' or 'stable since previous study', it is telling you that the radiologist had an earlier scan to compare against. Understanding that one fact makes the rest of the report much easier to read.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed September 2026
- A comparison was made — These phrases only appear when the radiologist had a previous scan to measure your current one against.
- Stable is the goal for many treatments — Holding disease steady is a recognised treatment aim, not a sign that nothing is happening.
- The report describes; your oncologist interprets — The radiologist states what changed. What that change means for your treatment is your oncologist's role.
- Images matter more than written reports — The radiologist needs the original scan files to measure and compare — a printed report from a previous scan is not enough.
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These phrases mean the radiologist compared your latest scan to a previous one. 'Stable since previous study' means no meaningful change was seen between the two scans. 'Interval change' means something has changed — better, worse, or different in character. Your oncologist interprets what that change means for your treatment.
What does each phrase in the report actually mean?
| Phrase you see | What the radiologist did | What it describes |
|---|---|---|
| Stable since previous study | Compared today's scan to the prior one and found no significant change | The disease appears unchanged between the two scans |
| No significant interval change | Measurements fell within expected variation between scans | Functionally the same as stable — no meaningful change seen |
| Interval increase / worsening | Found growth, spread, or higher activity than the prior scan | Change in the direction of more disease — your oncologist will advise on next steps |
| Interval decrease / interval response | Found shrinkage or reduced activity compared to the prior scan | Change in the direction of less disease |
| Cannot compare — no prior study available | No earlier scan was available to the radiologist on the day | Today's scan was read alone; no comparison was possible |
What should I bring to an assessment scan?
- Bring the CD or digital file of every previous scan, including those done at another centre or in another city
- Tell the booking team where your last scan was done — they may be able to request the images in advance
- If your last scan was done privately, carry both the written report and the image files yourself
- If this is your first scan ever, say so — your team will record it as the baseline for all future comparisons
- If scans were done abroad, bring the original image files; a printed translation of the report is not the same thing
What do the comparison words in my report mean?
- Interval
- The period of time between your previous scan and the one just done. 'Interval change' means a change that occurred during that gap.
- Prior study / previous study
- The earlier scan the radiologist used as a comparison. If no prior study was available, no comparison was possible and the report will say so.
- Baseline
- The very first scan, usually taken before treatment started. All future scans are ultimately measured against it, even when the immediate comparison is to the most recent one.
- Response assessment
- A scan read specifically to judge whether treatment is working, using formal criteria such as RECIST or PERCIST. This is different from a routine follow-up scan.
- SUV (PET reports only)
- A number measuring how actively a tissue is absorbing the scan tracer. A change in SUV between scans is one way the radiologist assesses whether disease has increased or decreased.
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Is 'stable since previous study' good news?
Stable means the disease has not grown and has not spread on today's scan. For most people in active treatment, holding disease steady is what the treatment is designed to do.
Whether it is good news in your situation depends on what your treatment is intended to achieve. Some treatments aim to shrink disease visibly; others aim to keep it stable for as long as possible. Your oncologist will explain which goal applies to you.
Stable is not a reason for alarm and it is not a reason to stop treatment. It is one data point that your oncologist reads alongside your symptoms, your blood results, and how you feel.
What happens when there are no prior scans to compare?
If this is your first scan, the radiologist describes what they see on the day but cannot say whether anything has changed. That scan becomes your baseline — the reference every future scan will be measured against.
If you have had scans at another centre that were not available on the day, the radiologist will note this. The report may then be incomplete because no comparison could be made.
Bringing the actual image files — not just the written report from the previous scan — is the most useful thing you can do before an assessment. Radiologists need the images to make measurements, not just a description of them.
Did you know?
The radiologist who reads your scan cannot see your symptoms, your blood results, or your treatment history. They compare images and describe what they find.
The clinical meaning — what any change means for your care — is something only your oncologist can tell you, with your full picture in front of them.
Source: ESMO Clinical Practice Guidelines on imaging assessment in oncology
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Explore 94 more Understanding Your PET-CT Report topics
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- 'Deauville Score' on a Lymphoma PET Report
- 'FDG Avid': What It Means on Your Report
- 'Hypermetabolic': What the Word Actually Means
- 'Hypometabolic' and 'Photopenic' Findings
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- 'Krenning Score' on a DOTANOC or DOTATATE Report
- 'Lymphadenopathy' on Your PET Report
- 'Metabolically Active Disease': What It Tells You
- 'Metastasis' and 'Distant Spread' on Your Report
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- Uptake After Radiotherapy: Inflammation or Disease?
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- What Causes a False Positive on a PET Scan?
- What Happens If Two Scans Disagree?
- Which Cancers Do Not Show Well on PET-CT?
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Incidental Findings
- A Second Unrelated Cancer Found on PET-CT
- An Incidental Bone Finding on PET-CT
- An Incidental Breast Finding on PET-CT
- An Incidental Kidney or Adrenal Finding
- An Incidental Liver Lesion on PET-CT
- An Incidental Lung Nodule Found on PET-CT
- An Incidental Prostate Finding on PET-CT
- An Incidental Thyroid Nodule on Your PET Scan
- Do All Incidental Findings Need Investigation?
- Focal Bowel Uptake: Could It Be a Polyp?
- Incidental Findings on a PET-CT Scan: What They Are
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- Interim PET Scan During Chemotherapy: Why It Is Done
- Metabolic Response vs Size Response: Why They Differ
- PERCIST Criteria: How Metabolic Response Is Measured
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SUV Values Explained
- Comparing SUV Between Two Scans: Is It Meaningful?
- Does a Higher SUV Mean a More Aggressive Cancer?
- Factors That Change Your SUV Reading
- High SUV but Not Cancer: When the Number Misleads
- Is My SUVmax of 4 High? Reading Your Specific Number
- Low SUV but Still Cancer: The PET-Negative Cancers
- SUV in Non-Cancer Conditions
- SUVmax, SUVmean and SUVpeak: What Is the Difference?
- What Is SUV on a PET Scan?
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Common questions
Frequently asked questions
Does 'stable' mean the treatment is working?
Stable means the disease has not grown on this scan. Whether that counts as the treatment working depends on what your treatment was designed to do. Some treatments aim to hold disease steady rather than shrink it — stable is then the expected and wanted result. Others aim for visible shrinkage. Ask your oncologist which goal applies to your situation and how this result measures against it.
Can a scan say 'interval change' without explaining what changed?
'Interval change' is a summary phrase that usually appears in the header or conclusion of a report. The body of the report will always describe what changed: which lesion, whether it grew or shrank, by approximately how much, and whether new findings appeared. If you cannot find that detail, ask your oncologist to walk you through the relevant section. The summary line is never the full answer.
Why do I need to bring my old scans if the report has already been written?
The written report describes what the radiologist saw, but it does not contain the images. When comparing scans, the radiologist needs to measure the actual images — the size of a lesion in millimetres, how much tracer it is absorbing on PET. None of that can be done reliably from another radiologist's written description. Bringing the CD or digital file allows a proper, measured comparison.
What is the difference between 'stable' and 'complete response'?
Stable means no meaningful change — the disease is still visible on the scan but not growing. Complete response means no detectable disease is visible at all. They are very different findings. Complete response is relatively uncommon and varies by cancer type. If your report says complete response, ask your oncologist what that means for your ongoing treatment plan, because next steps differ depending on cancer type and stage.
My PET report says 'interval increase in SUV' — is that always a bad sign?
An increase in SUV means the tissue is absorbing more tracer than it did last time, which can indicate more active disease. It can also reflect inflammation, infection, or the timing of the scan relative to your last treatment dose. SUV is one measurement among several and should not be read in isolation. Your oncologist will interpret it alongside the rest of the report and your clinical picture before drawing any conclusions.
Does each scan compare to the most recent one, or to the very first one?
Usually both. The most recent scan is the main comparison — it shows what has happened since your last assessment. The baseline scan, taken before treatment began, is the broader reference showing the overall direction of change across your whole treatment course. Your oncologist may refer to both when discussing your results. If you are unsure which comparison is being made in a particular sentence of the report, ask them to clarify.