Jerome Graber1, George Daily-Lyles2
1Neurology and Neurosurgery, 2Neurosurgery, University of Washington
Objective:
To report a case of spontaneous shrinkage of recurrent anaplastic oligodendroglioma and review data on timing of imaging responses to various treatments.
Background:
Oligodendrogliomas that are IDH1-mutant & 1p/19q-codeleted have varied growth patterns but measurable responses to treatment are uncommon. Imaging growth rates correlate with aggressive behavior and treatment responses. Kinetic evaluations of lower grade gliomas before and after treatment with CCNU have shown significant impacts on tumor growth occurring as late as three years after chemotherapy. Spontaneous tumor shrinkage is inadequately characterized. This emphasizes the importance of carefully interpreting treatment outcomes and expectations.
Design/Methods:
Case report.
Results:
A 33-year-old man with a recurrent anaplastic oligodendroglioma (WHO grade III, IDH1-mutant, 1p/19q codeleted). Initial diagnosis occurred at age 26 after resection. After adjuvant therapy with radiotherapy and temozolomide, the patient presented with a growing mass in the right medial frontal lobe in March 2021. Resection revealed a mitotically active tumor, and post-operative management included further cycles of temozolomide. The patient declined additional treatment options after December 2021.
After chemotherapy in December 2021, the tumor showed gradual growth over the next 2.5 years. Thirty three months after last chemotherapy, MRI showed a sudden spontaneous decrease in enhancing tumor size. The area of tumor shrinkage was new after radiation 7 years prior, and was not present at the time of prior chemotherapy, making delayed response or pseudoresponse extremely unlikely. The growth rate of this patient’s tumor prior to regression matched literature on oligodendrogliomas exhibiting slow growth post-treatment cessation.
Conclusions:
This case highlights the challenges spontaneous tumor regression presents when interpreting response rates in clinical data. Given imaging growth rates have been predictors of malignancy, spontaneous tumor regression stresses the need for caution in assessing the effectiveness of therapies and the importance of controlled, comparative trials with long term follow up to assess response rates.
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