1071 - A Prospective Study to Evaluate the Impact of Radiotherapy Technique - 3DCRT vs. Hippocampal Sparing Volumetric Modulated Arc Therapy (hsVMAT) - on Neurocognitive Function (NCF) in Adults with Grade 2-3 Gliomas

Purpose/Objective(s): Data on effects of adjuvant radiotherapy (RT)/chemotherapy and hippocampal avoidance on NCF in grade 2-3 gliomas is sparse. This study aimed to assess (a) longitudinal change in NCF till 6 months post-RT, and (b) difference in NCF between 3DCRT and hsVMAT.

Materials/Methods: Adults (age 18-60 years, KPS =60, MMSE score =18, no pre-existing neurologic disease) with newly diagnosed grade 2-3 gliomas planned for adjuvant therapy [54-60 gray (Gy) +/- concurrent and adjuvant chemotherapy] were randomized to either 3DCRT or hsVMAT arms. For hsVMAT, hippocampal constraints used were: D98% <9 Gy, Dmax <16 Gy, and D40% <7.4 Gy. Target coverage was prioritized over hippocampal dose. NCF was assessed pre-RT, post RT, and at 3 and 6 months, using Montreal Cognitive Assessment (MOCA), and Post Graduate Institute Memory Scale (PGI MS) to assess different domains of memory function. Data were analyzed using statistical software. Paired t-test and repeated measures ANOVA were used to compare median scores between both groups and change over time.

Results: From January 2023 to April 2024, 80 patients (median age 39.64 years, male:female 2:1) were enrolled. Most common symptoms were seizures (65%), headache (57.5%), and limb weakness (17.5%). Frontal lobe involvement was seen in 68.75% and temporal in 42.5%; 10% patients had disease in parietal lobe, thalamus, or cerebellum. Reported surgery extent was gross or near total excision in 76.25%, subtotal excision in 13.75%, and stereotactic biopsy in 10%, but postoperative MRI showed residual tumor in 70%. Histology included oligodendroglioma (33.8% gr 2, 37.5% gr 3), astrocytoma (13.8% gr 2, 11.3% gr 3) or unspecified (3.8%). Disease involved hippocampus in 42.5% (bilateral in 5%). RT dose was 60 Gy in 48.75% (all with concurrent temozolomide, TMZ) and 54 Gy in 51.25% (concurrent TMZ in 20% as per Pignatti criteria). In hsVMAT arm, all three constraints were achieved for at least one hippocampus in 10%; D98% was achieved in 67.5%. Six month NCF assessment was completed by 83.75% patients. Mean scores of NCF tests are noted in table 1; no difference was seen between both arms at baseline or on follow up.

Conclusion: In lower grade gliomas without severe cognitive impairment, decline in NCF was not observed till 6 months post-RT; outcomes were similar for both 3DCRT and hsVMAT, unlike previous studies in brain metastases and high grade gliomas. The lack of difference may be attributable to hippocampal involvement in >40% patients and short follow up. Cognitive prognosis in this group may depend on additional factors beyond hippocampal doses.