Response assessment
End-of-Treatment PET Scan: — What It Decides
This is the scan your whole course of treatment has been building toward. The result tells your oncologist whether the cancer responded, whether treatment is finished, and what happens next — and it carries significant weight for you and your family.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed September 2026
- Metabolic, not just structural — The scan measures whether cancer cells are still active, not only whether a mass is still visible on imaging.
- Uses standard categories — Results are expressed in defined response categories that your team uses to make the next decision.
- A number is not a verdict — A Deauville score or response category is a clinical tool that informs your oncologist's judgement, not a standalone answer.
- Residual mass is not always active disease — Something still visible on the scan may be scar tissue rather than living cancer. Biopsy or follow-up imaging sometimes resolves this.
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An end-of-treatment PET scan is done after your final cycle of therapy to measure how the cancer has responded. The result — expressed as a response category such as complete or partial response, or as a Deauville score in lymphoma — directly informs whether treatment is finished, extended, or changed.
When is this scan done, and what does it measure?
The scan is done after your final cycle of treatment, usually after several weeks have passed. Scanning too soon can produce misleading results, because normal inflammatory changes from chemotherapy or radiation also show FDG uptake — and that fades once the inflammation settles.
It measures metabolic activity — how much glucose the cells in a lesion are absorbing. Cancer cells that are still active absorb glucose at a higher rate than most normal tissue. The FDG tracer injected before the scan makes this difference visible.
Most scanners combine PET with CT in a single session. PET shows metabolic activity; CT shows size and structure. Your oncologist reads both together, because a mass can shrink without becoming inactive, or remain structurally but be metabolically quiet.
What do the response categories mean?
| Response category | What the scan shows | What typically follows |
|---|---|---|
| Complete Metabolic Response (CMR) | No FDG uptake above background indicating active disease | Treatment ends; a surveillance schedule begins |
| Partial Metabolic Response (PMR) | Uptake has reduced but not reached the threshold for complete response | Further therapy, consolidation, or observation — depends on cancer type and protocol |
| Stable Metabolic Disease (SMD) | Uptake has not changed meaningfully from the baseline scan | Indicates current treatment is not working well enough; a different approach is discussed |
| Progressive Metabolic Disease (PMD) | Uptake has increased, or new lesions have appeared | Treatment change is needed; your oncologist will discuss alternatives |
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What do the terms on your PET scan report mean?
- FDG (fluorodeoxyglucose)
- The radioactive tracer injected before the scan. It is a form of glucose. Active cancer cells absorb it at a higher rate than most normal tissue, making them visible on the scan image.
- SUV (Standardised Uptake Value)
- A number that quantifies how much FDG a lesion has absorbed. Your report may list an SUV for individual lesions. Higher values suggest more metabolic activity, but the number is always read in clinical context — not in isolation.
- Deauville score
- A five-point scale used in lymphoma to grade FDG uptake, comparing a lesion to two reference points in the body. Per Lugano criteria — the international standard endorsed by ESMO, ASCO, and NCCN — scores of 1 to 3 indicate complete metabolic response in most lymphoma protocols.
- Lugano criteria
- The internationally accepted standard for assessing lymphoma response on PET and CT, endorsed by ESMO, ASCO, and NCCN. It defines the response categories and underpins the Deauville scoring system.
- Residual mass
- Tissue that remains visible on imaging after treatment ends. A residual mass is not automatically active disease — in lymphoma particularly, it is often scar tissue (fibrosis). Biopsy or follow-up imaging is sometimes used to distinguish between the two.
- Background uptake
- The normal FDG activity in healthy tissue. Whether a lesion is considered significant is measured against this baseline — not as an absolute number on its own.
Questions families ask when they see the result
Something is still showing on the scan — does that mean treatment failed?
Not necessarily. A residual mass after treatment may be scar tissue from the treatment itself rather than living cancer. In lymphoma, this is common — fibrosis after chemotherapy can appear on imaging but be metabolically inactive. Your oncologist may recommend a biopsy to confirm what the remaining tissue is, or a follow-up scan after several months to see whether it is stable or changing. A result that appears worrying when you first read it often means something quite different in clinical context.
What does 'complete response' actually mean for me?
Complete metabolic response means the scan shows no FDG uptake above background indicating active disease. It does not mean no cancer cells exist anywhere in the body — PET scans detect activity above a threshold, not individual cells. What it does mean is that your cancer has responded as well as current imaging can show, giving your oncologist a strong basis for the decisions ahead. Understanding both what it means and what it does not guarantee helps you hear the result clearly.
My report shows a Deauville score of 3 — is that good or bad?
A score of 3 means FDG uptake in the lesion is approximately at liver level — the midpoint of the scale. Per Lugano criteria endorsed by ESMO and ASCO, a score of 3 is classified as complete metabolic response in most standard lymphoma protocols. However, some clinical trials and specific protocols treat a score of 3 differently, particularly when it has not improved from an interim scan. The right interpretation depends on your cancer type, the protocol you are on, and your oncologist's assessment. Ask your team what a score of 3 means specifically in your situation.
Why is my doctor ordering more tests even though the scan looks clear?
A clear end-of-treatment scan begins surveillance, not certainty. Follow-up scans and blood tests at regular intervals are standard practice after a complete response — they are designed to detect a relapse early, when it is most treatable. Your oncologist may also need to confirm a borderline result with a biopsy, or your protocol may include consolidation therapy for high-risk features even after a complete response. Additional tests after a good scan are part of the plan, not a sign that something is wrong.
A whole-body PET-CT at CION is Rs 10,499 — among the lowest published prices in Hyderabad — with a free Rs 950 oncologist consultation to talk through your report. Indicative price, as of September 2026.
Explore 94 more Understanding Your PET-CT Report topics
Response Assessment Scores & Criteria
- Complete Metabolic Response: What It Means
- Deauville Score 1 to 5: The Lymphoma Scale Explained
- End-of-Treatment PET Scan: What It Decides
- How Doctors Judge Whether Treatment Is Working on PET-CT
- Interim PET Scan During Chemotherapy: Why It Is Done
- Metabolic Response vs Size Response: Why They Differ
- PERCIST Criteria: How Metabolic Response Is Measured
- Partial Metabolic Response: Is That Good Enough?
- Progressive Metabolic Disease: What Happens Next
- RECIST vs PERCIST: Size vs Activity
- Stable Metabolic Disease: Good News or Bad?
- Tumour Flare and Pseudoprogression on PET
- What Is a Deauville 3 and Why Is It Ambiguous?
- Why the Scan Says One Thing and You Feel Another
False Positives, False Negatives & Pitfalls
- Bladder, Kidney and Ureter Activity on PET
- Bone Marrow Uptake After Growth Factor Injections
- Bowel Uptake: Normal, Inflammation or Something Else?
- Brown Fat Uptake: A Common Cause of Confusing Findings
- Does a Suspicious PET Finding Always Need a Biopsy?
- Getting a Second Read of Your PET-CT Images
- How Often Is a PET-CT Scan Wrong?
- Muscle Uptake After Exercise or Injections
- Thymic and Rebound Uptake in Younger Patients
- Uptake After Radiotherapy: Inflammation or Disease?
- Uptake at a Biopsy or Surgery Site
- What Causes a False Negative on a PET Scan?
- What Causes a False Positive on a PET Scan?
- What Happens If Two Scans Disagree?
- Which Cancers Do Not Show Well on PET-CT?
- Why the Brain Always Lights Up on PET
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
- Incidental Heart Findings on a Cancer PET Scan
- The Cost of Chasing an Incidental Finding
- What to Ask Your Doctor About an Incidental Finding
Infection, TB & Inflammation on PET
- Can Tuberculosis Look Like Cancer on a PET Scan?
- Dental Infection and Jaw Uptake on PET
- Fungal Infection and Abscess on PET-CT
- How Long Should You Wait After an Infection Before a PET Scan?
- If It Might Be Infection, What Test Comes Next?
- Inflammation After Injections, Vaccines and Cannulas
- Old Healed TB and Calcified Nodes on PET-CT
- PET-CT for Fever of Unknown Origin
- PET-CT for Suspected Infection in Implants and Prostheses
- PET-CT for Vasculitis and Inflammatory Conditions
- Pneumonia and Recent Chest Infection on PET
- Sarcoidosis on PET-CT: The Great Mimic
- TB or Cancer? How Doctors Tell Them Apart
- Thyroid Uptake on PET: Diffuse vs Focal
Reading Your Report: Core Terms
- 'Cannot Be Excluded' and Other Cautious Phrases
- '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
- 'Impression' vs 'Findings': Which Section Should You Read?
- 'Interval Change' and 'Stable Since Previous Study'
- '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
- 'Mildly FDG Avid' vs 'Intensely FDG Avid'
- 'No Abnormal FDG Uptake': Is That a Clear Scan?
- 'Physiological Uptake': Normal Areas That Always Light Up
- 'Residual Disease' vs 'Complete Metabolic Response'
- 'Sub-Centimetre Node' and Why Size Matters on PET
- 'Suspicious for Malignancy': How Certain Is That?
- How Long Does a PET-CT Report Take?
- How to Read Your PET-CT Report: A Section-by-Section Guide
- Should You Read Your Own PET-CT Report Before the Consult?
- TNM Staging on a PET-CT Report
- Why Your Report Mentions the Liver and Blood Pool
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?
- What Is a Normal SUV Value?
- What SUV Value Indicates Cancer?
- Why Blood Sugar Changes Your SUV Result
- Why Did My SUV Go Down but Not to Zero?
- Why Did My SUV Go Up After Treatment?
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Common questions
Frequently asked questions
How many weeks after chemotherapy is the end-of-treatment PET scan done?
The timing depends on your cancer type, the drugs used, and your specific protocol. Scanning too soon can produce misleading results because inflammatory changes from treatment also show FDG uptake that has nothing to do with residual cancer. Your oncologist schedules it when those changes have had time to settle. Ask your team when your scan is booked and why that interval was chosen for your situation.
Is the end-of-treatment PET scan different from the interim scan done during treatment?
They use the same machine and tracer, but they answer different questions. An interim scan is done partway through treatment to assess whether the cancer is responding and whether the plan needs to change mid-course. The end-of-treatment scan assesses the final depth of response after all planned cycles are complete. Your oncologist usually reads the two together, and the change between them carries its own clinical meaning.
My oncologist described the result as 'equivocal'. What does that mean?
Equivocal means the result sits in an uncertain zone — not clearly a complete response and not clearly active disease. Some results genuinely do not fall into a neat category, and that is not evasion on your oncologist's part. They may respond with a biopsy, a follow-up scan in a few months to see whether the appearance changes, or a multidisciplinary discussion. Ask what specific feature is uncertain and what the next step is intended to establish.
Does a complete response mean the cancer will not come back?
A complete metabolic response means treatment has worked as well as current imaging can show. It does not mean relapse is impossible. The probability of relapse depends on your cancer type, the features of your disease, and how it behaved during treatment. Your oncologist will give you their assessment for your specific situation — that conversation is more meaningful than any general statement about the result.
What happens if I am not in complete response — are there still options?
A partial or no response does not mean options have ended. It means the current treatment has not achieved the depth of response needed, and a different approach is indicated. Depending on your cancer type and your overall fitness, options may include a different treatment regimen, radiation to areas of remaining disease, or a clinical trial. Your oncologist will explain what the evidence supports for your specific situation. The end-of-treatment scan is a decision point, not a final verdict.
Should I ask for a copy of my PET scan report?
Yes. You are entitled to your reports, and having a copy means you can refer to exact wording during your appointment, seek a second opinion, or transfer care without delay. Reading a PET report without clinical context can be alarming — the language is technical and numbers without reference ranges look frightening. Ask your oncologist to walk you through what the report says and what it means for your plan before you read it alone.