Abstract
Background Immunotherapy represents an effective therapeutic approach for many malignant diseases
that were previously difficult to treat. However, since immunotherapy can lead to
atypical therapy response patterns in the form of pseudo-progression or mixed responses
and comprise an altered spectrum of adverse reactions, they present a new challenge
for oncologic imaging. Detailed knowledge in this area is essential for oncologic
clinical radiologists, since the radiological report is a cornerstone of response
assessment, and increasingly influences therapy regimens and coverage by health insurances.
Method This white paper is based on an expert meeting in Frankfurt am Main and subsequent
discussions between the authors. Based on the iRECIST criteria, it is intended to
provide orientation for a response assessment of oncologic patients undergoing immunotherapy
that can be applied in the clinical routine.
Results Radiological therapy monitoring outside clinical studies is subject to inherent limitations,
but should be performed based on iRECIST criteria, according to the opinion of the
expert panel. It should be taken into account that immunotherapies can in principle
lead to pseudo-progression and autoimmunological side effects. Since radiological
follow-up is currently the only method to accurately distinguish real progressive
disease from pseudo-progression, clinically stable patients with disease progression
under immunotherapy should undergo additional short-term follow-up imaging according
to the suspected diagnosis. Biopsy should be used cautiously and predominately in
curative settings.
Conclusion For response assessment of immunotherapy in clinical studies, the new iRECIST criteria
were published in 2017. Outside studies, the application of iRECIST criteria in the
clinical routine is subject to several limitations. The recommendations implied in
these criteria can, however, be used in conjunction with the current literature as
a guideline in clinical practice and outside studies.
Key points:
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Novel immunotherapies can cause atypical response patterns like pseudo-progression
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Compared to real progressive disease, pseudo-progression occurs rather rarely, yet
can influence therapy
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Short-term follow-up according to iRECIST can help to distinguish pseudo-progression
from real progression
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Hence, radiological follow-up outside clinical studies should be oriented towards
iRECIST criteria
Citation Format
Key words
staging - treatment effects - treatment planning
