Pseudoresponse

Pseudoresponse is a term used in medical imaging and oncology to describe an apparent improvement of a disease on imaging studies that does not reflect a true biological or clinical response. It is most commonly described in patients with cancer treated using anti-angiogenic therapies, where imaging changes may mimic tumor shrinkage or stabilization even though tumor cells have not substantially decreased.

In neuro-oncology, pseudoresponse is particularly associated with anti-angiogenic drugs such as VEGF inhibitors in gliomas (for example, glioblastoma). These agents can decrease vascular permeability and reduce edema, leading to reduced contrast enhancement on MRI and an impression of tumor regression. Because edema and contrast leakage influence imaging findings, the apparent radiographic response may overestimate actual tumor control.

Clinical significance centers on the risk of misinterpreting imaging changes as genuine treatment success. This can affect treatment decisions, timing of alternate therapies, and prognosis. Distinguishing pseudoresponse from true response typically relies on a combination of imaging features, clinical status, and, when feasible, follow-up imaging after a set interval. Advanced imaging techniques, such as perfusion MRI, diffusion-weighted imaging, and spectroscopy, can aid assessment, but pathological confirmation remains the definitive determination when possible.

Response assessment guidelines in neuro-oncology, including RANO and iRANO criteria, acknowledge pseudoresponse and advocate cautious interpretation of early imaging changes during anti-angiogenic therapy, emphasizing the integration of imaging, clinical data, and longitudinal follow-up.