Diagnosis & Imaging
Pseudoresponse
Pseudoresponse is an apparent improvement on imaging from certain drugs (like bevacizumab) that reflects reduced enhancement rather than true tumor shrinkage.
In short: Pseudoresponse
- It is an apparent imaging improvement that is not true tumor shrinkage.
- It is associated with anti-angiogenic drugs like bevacizumab.
- It reflects reduced enhancement, not tumor reduction.
- It complicates assessment of treatment response.
What it is
Pseudoresponse is an apparent improvement on imaging — particularly decreased contrast enhancement — caused by certain drugs (such as bevacizumab, an anti-angiogenic agent) that does not necessarily reflect true tumor shrinkage. It is essentially the opposite challenge from pseudoprogression.
Understanding Pseudoresponse
Anti-angiogenic drugs like bevacizumab work in part by reducing the leakiness of tumor blood vessels, which decreases contrast enhancement and swelling on MRI. This can make scans look dramatically improved soon after starting the drug — but the reduction in enhancement reflects the drug's effect on blood vessels rather than a true reduction in the amount of tumor, and non-enhancing tumor may persist or progress despite the improved-looking scan. This "pseudoresponse" can give a falsely reassuring impression. Recognizing it is important so that apparent improvement is interpreted correctly, with attention to non-enhancing tumor (seen on FLAIR/T2) and the overall clinical picture rather than enhancement alone. Modern response criteria (such as RANO) account for these treatment effects. Understanding pseudoresponse in gliomas clarifies an apparent improvement that may not reflect true tumor reduction.
Why it matters
Understanding pseudoresponse helps patients and families interpret improved-looking scans on certain drugs cautiously — reduced enhancement may reflect the drug's effect on blood vessels rather than true tumor shrinkage.
Common questions
What is pseudoresponse?
An apparent imaging improvement that is not true tumor shrinkage.
What causes it?
Anti-angiogenic drugs like bevacizumab.
Why does it matter?
It can give a falsely reassuring impression of response.
Bottom line
Pseudoresponse is an apparent imaging improvement from drugs like bevacizumab that reflects reduced enhancement rather than true tumor shrinkage, complicating response assessment.
Browse all 265 Glioma definitions
Read the Glioma patient guides
Not sure which page you need? Put words to it with the symptom navigator