Interim PET in Lymphoma: — The Scan That Changes Treatment

The Deauville score is a five-point scale used internationally to report PET findings in lymphoma. Each point corresponds to how much metabolic activity the scan shows compared to reference tissues in the body. Scores 1 to 3 are generally considered negative — the lymphoma is responding. Scores 4 and 5 indicate significant remaining activity. It gives your haemato-oncologist a consistent, reproducible way to describe the scan result and to make treatment decisions against published criteria from ESMO, NCCN, and the Lugano classification.

No. A positive interim PET means the response to the first two cycles has been inadequate, not that the disease is beyond treatment. Lymphoma — including Hodgkin lymphoma and diffuse large B-cell lymphoma — can respond to second-line regimens, and some patients reach deep remission through a different treatment path. The interim scan is a checkpoint, not a verdict. What happens next is a decision for your haemato-oncologist, who will review all available information before advising you on the options.

Yes — both false positive and false negative results are possible. A false positive most often occurs because of infection, inflammation, or treatment-related tissue changes that increase glucose uptake in non-cancerous tissue. A false negative — where active lymphoma is not detected — is less common but can occur with small lesions or certain slower-growing subtypes. This is why the result is always interpreted alongside the clinical picture, and why a biopsy of a specific lesion is sometimes done before any treatment change is made.

Your haemato-oncologist will review the result, usually within a few days of the scan. If it is negative, you will generally continue on your current treatment plan toward the end-of-treatment assessment. If it is positive or uncertain, your team will discuss whether to change the regimen, investigate a specific lesion further, or intensify treatment. An end-of-treatment PET is done after all planned cycles are complete and is the formal assessment of whether complete metabolic response has been achieved.

No. They are different scans done at different stages and for different purposes. The interim PET, done after two cycles, is a mid-course check used to make a treatment decision. The end-of-treatment PET, done after all cycles are complete, is the formal assessment of whether the lymphoma has reached a complete metabolic response. Both use the Deauville scoring system, but they answer different clinical questions and carry different implications for what comes next.

At CION, PET-CT scans are coordinated with partner imaging centres — you do not need to arrange this yourself. Your care team will time the referral so the scan falls at the correct point in your treatment cycle. After the scan, the report is reviewed by your haemato-oncologist alongside the imaging findings, and the result is discussed with you before any decision is made about what happens next.