Partial Response and Complete Response — What Do the Words Actually Mean?

Complete response means every target and non-target lesion has disappeared on imaging, with any lymph nodes shrunk back to a normal size. Partial response means the tumour is measurably smaller than at baseline — under RECIST 1.1, the tumour-measurement framework referenced in NCCN and ASCO guidance, this means the sum of target-lesion diameters has fallen by at least 30% — but some visible disease still remains on the scan.

Both are recorded as genuine response categories, not a pass/fail grade on how treatment is doing. The category simply describes how much visible disease is left on this particular scan, compared with the scan taken before treatment started.

Response-assessment PET-CT and other imaging for CION patients is coordinated through partner imaging centres. This page explains general reporting terminology; it does not interpret your specific scan.

Categories shown follow RECIST 1.1, referenced in NCCN and ASCO guidance for solid-tumour reporting, indicative as of August 2026. This table is general education, not an interpretation of any individual scan — your oncologist assigns the category that applies to your report.

Yes, generally — a partial response means the tumour has genuinely shrunk under a defined clinical threshold, not that treatment has fallen short of some better outcome. On immunotherapy specifically, a partial response is very often a stable, durable result that continues for a long time without ever becoming a complete response, and that pattern alone does not mean the drug is underperforming.

What matters more than the single label is the trend across your follow-up scans — whether the response is holding, continuing to shrink further, or turning around — which is a conversation for your oncologist, not something this page can assess from a report alone.

1. 1

   The first response is recorded as a baseline for comparison

   Once a partial response is confirmed, later scans are compared against it, not just against the original pre-treatment scan.

2. 2

   Continued immune activity can deepen the response further

   Because immunotherapy works through ongoing immune activity rather than a single dose effect, shrinkage can continue on treatment months after it first appeared.

3. 3

   A scan showing no remaining visible disease reclassifies it as complete

   When all target and non-target lesions have disappeared on a follow-up scan, the category is updated from partial to complete response.

4. 4

   Many patients simply stay at a stable partial response

   Not converting to a complete response is common and is still considered a good, ongoing outcome — it is not a sign that the response is failing.

At your first scan, your radiologist marks out a small set of "target lesions" — the clearest, most measurable areas of disease — and records the sum of their longest diameters. Every later scan re-measures those same target lesions and compares the new sum against that baseline, which is what produces the percentage shrinkage or growth behind each response category.

Non-target lesions and lymph nodes are tracked too, described in general terms such as "present", "resolved" or "unequivocal progression", and any genuinely new lesion is recorded separately rather than folded into the existing target-lesion measurement.

• Biomarker and blood-test trends — tumour markers or inflammatory markers moving in the same direction as the scan add confidence to the category, though they don't change it on their own.
• Symptom and performance-status changes — how you're functioning day to day is recorded at every visit alongside the imaging result.
• Whether the result needs confirming — under iRECIST, a first-seen change is sometimes labelled "unconfirmed" pending a repeat scan before it is treated as final.
• How early in treatment the scan was taken — response can genuinely continue to develop over further cycles, so one scan is a snapshot, not the final word.

This page explains general terminology only. If your report combines scan and biomarker findings in a way you don't follow, ask your oncology team to walk through it together rather than piecing it together yourself.

• A Confirmation Scan Was Ordered: What Does That Mean? — why an "unconfirmed" result on your report leads to a repeat scan before your category is finalised.
• SUV Values on PET After Immunotherapy: Why They Can Rise — a related number on PET reports that can rise for reasons that don't mean your response has worsened.
• New Lymph Nodes Lighting Up on Your Scan — what a genuinely new finding means separately from your existing target-lesion response category.
• Immunotherapy at CION Cancer Clinics — the full picture of how CION supports patients through the immunotherapy decision and journey.

This page explains general response-category terminology used on cancer scan reports, for education only, and does not interpret any individual patient's report. Response-assessment PET-CT is coordinated at partner imaging centres. Bring your report to a consultation for a doctor's assessment of what it means for you.

Thousands of families have sat with unfamiliar report wording

A response category you don't recognise can be worrying to read alone. Our oncologists take the time to explain what it means and what typically happens next.