Oligoastrocytoma NOS with pseudoprogression


The diagnosis of pseudoprogression can be difficult and knowledge of timing of the scan relative to chemoradiotherapy is crucial (typically ~3 months post end of chemoradiotherapy, but commonly seen within 0 - 6 months). 

This patient was also more likely to demonstrate pseudoprogression as their tumor is MGMT methylated (and thus alkylating agents e.g. temozolomide will have greater efficacy). 

It is also crucial to realize that it is not a question of pseudoprogression OR persistence presence of tumor (or even probably tumor growth); both can be occurring simultaneously. It is really a question of determining which process is dominant and accounts for the imaging features.