Anaplastic Oligodendroglioma - Is Adjuvant Radiotherapy Mandatory following Maximal Surgical Resection?: Grade 3 Oligo Radiotherapy.

Background: Current anaplastic oligodendroglioma (AO) management strategies involve surgical resection followed by adjuvant radiotherapy and/or chemotherapy. We investigated a subset of patients at our institution with AO, who, based on their treatment preferences, received surgery without any form of adjuvant therapy. This subset of patients was compared to a cohort with AO who received adjuvant therapy in order to investigate any differences in clinical and survival outcomes.

Methods: A retrospective review of all AO patients treated by the senior author was undertaken between 1994 and 2018. A total of thirty-three cases were identified. Eleven had surgery alone, and twenty-two had surgery with adjuvant therapy. Progression free (PFS) and overall survival (OS) were compared between cohorts and potential confounders were addressed.

Results: Gross total resection was achieved in 29 patients, and near total resection in 4 patients. PFS was not statistically different between patients treated with surgery alone versus patients receiving surgery plus adjuvant therapy (surgery alone: 84 ± 16 months; surgery with radiotherapy: 60 ± 9 months; p = 0.08). In addition, OS was also not statistically different between these groups (surgery alone: 215 ± 17 months; surgery with therapy: 241 ± 22 months; p = 0.44).

Conclusions: It is reasonable to consider a "watch and monitor" surveillance strategy in patients who decline adjuvant radiotherapy following surgical resection of their AO. Patients should be made aware that this treatment plan is not standard within current models of care for AO.