Abstract
Background
Incidence and characteristics of pseudoprogression in isocitrate dehydrogenase-mutant high-grade gliomas (IDHmt HGG) remain to be specifically described.
Methods
We analyzed pseudoprogression characteristics and explored the possibility of pseudoprogression misdiagnosis in IDHmt HGG patients, treated with radiotherapy (with or without chemotherapy), included in the French POLA network. Pseudoprogression was analyzed in patients with MRI available for review (reference cohort, n=200). Pseudoprogression misdiagnosis was estimated in this cohort and in an independent cohort (control cohort, n=543) based on progression free survival before and after first progression.
Results
In the reference cohort, 38 patients (19%) presented a pseudoprogression after a median time of 10.5 months after radiotherapy. Pseudoprogression characteristics were similar across IDHmt HGG subtypes. In most patients, it consisted in the appearance of one or several infracentimetric, asymptomatic, contrast-enhanced lesions occurring within 2 years after radiotherapy. The only factor associated with pseudoprogression occurrence was adjuvant PCV chemotherapy. Among patients considered as having a first true progression, 7 out of 41 (17%) in the reference cohort and 35 out of 203 (17%) in the control cohort were retrospectively suspected to have a misdiagnosed pseudoprogression. Patients with a misdiagnosed pseudoprogression were characterized by a time to event and an outcome similar to that of patients with a pseudoprogression but presented with larger and more symptomatic lesions.
Conclusion
In patients with an IDHmt HGG, pseudoprogression occurs later than in IDH-wildtype glioblastomas and seems not only frequent but also frequently misdiagnosed. Within the first 2 years after radiotherapy, the possibility of a pseudoprogression should be carefully considered.
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