Long term outcomes of central neurocytoma in a multi-institutional cohort: The role of radiotherapy and Ki-67.

Abstract

2089 Background: Central neurocytomas (CNs) are rare, WHO grade 2 brain tumors that can have relatively high recurrence rates following surgical resection. Owing to the rarity of CNs and limited robust data, the optimal use and timing of radiotherapy (RT) remain undefined, particularly in young adults with low mortality. Tumor proliferation index (Ki-67) may also predict CN recurrence rates, but there is no consensus on its utility in clinical practice. The present collaboration between Northwestern University and the Mayo Clinic describes long-term outcomes of CN as it relates to RT timing and Ki-67 level. Methods: Patients established between 1990-2025 with a tissue diagnosis of CN at Northwestern University and the Mayo Clinic were reviewed. Demographic, treatment, and tumor characteristics (histologic/molecular) were recorded. Recurrence free survival (RFS) and overall survival (OS) were calculated according to the Kaplan Meier-method. Results: Fifty-one patients with CN (51% male, 49% female)--with a median age of 26 years and 9.7 years median follow-up--were included. RFS at 2, 5, and 10 years for the cohort was 79%, 65%, and 59% respectively; OS at 10 years for the cohort was 94%, and no deaths were attributed to uncontrolled CN. Subtotal resection (STR) yielded 2- and 5-year RFS of 74% and 65%, while gross total resection (GTR) yielded 2- and 5-year RFS of 90% and 66%. Median Ki-67 of the cohort was 3%; RFS at 2 and 5 years for Ki-67 <3% was 82% and 76%, compared to 76% and 43% for Ki-67 ≥3% (p<0.02). In patients who underwent resection without adjuvant RT (n=35), those with STR had a 2- and 5-year RFS of 61% and 45%, and those with GTR had a 2- and 5- year RFS of 88% and 61%. Additionally, without adjuvant RT, RFS at 2 and 5 years for Ki-67 <3% was 73% and 64% versus 71% and 24% for Ki-67 ≥3%. Among patients without adjuvant RT and Ki-67 ≥3% (n=14), 2-year RFS was 60% after STR and 78% after GTR. Salvage RT after first recurrence (n=16) had a 5-year RFS of 81%, with a median follow-up of 4.1 years. Conclusions: We report one of the largest cohorts of CN with long-term follow-up. STR and/or Ki-67 ≥3% were associated with shorter RFS. Salvage RT at recurrence achieved durable long-term tumor control, and long-term (~10-year) mortality was low. In appropriately selected patients, observation after resection may be a reasonable initial strategy, with RT reserved for salvage. General cohort characteristics (n=51) with Ki-67 (n=39). Variable Number (%) Median Age (years) 26 (range: 5-57) Gender, Male:Female (M/F) 26:25 (51/49) Subtotal Resection 29 (57) Gross Total Resection 22 (43) Adjuvant Radiotherapy 16 (31) Salvage Radiotherapy 16 (31) No Radiotherapy 19 (38) Ki-67 ≥3 21 (56) Ki-67 <3 18 (44)