MNGI-03. ESTROGEN HORMONE REPLACEMENT THERAPY IN INCIDENTAL MENINGIOMA - A GROWTH RATE ANALYSIS

BACKGROUND Meningiomas are common intracranial neoplasms with female predominance and sharply rising incidence in the perimenopausal years. As they often express estrogen receptors, hormone replacement therapy (HRT) poses a theoretical risk inducing accelerated growth. Although HRT has been linked to slightly increased incidence, its actual effect on meningioma growth-rate had not been studied in a clinical population. AIM: We aimed to retrospectively compare tumor characteristics and grow-rates of incidental meningiomas of those with a ≥6-month history of estrogen-based HRT (e-HRT) before or during surveillance compared to those without (no-HRT). METHODS Forty females with e-HRT and 80 age-matched HRT-naïve females were identified from the NorthShore Incidental Meningioma Database. Tumor characteristics and diameters were analyzed on initial and all follow-up MRIs. Progression-free survival (PFS) was assessed. RESULTS Twenty-one patients completed e-HRT before, 10 started before and continued during, and 9 started e-HRT during surveillance. Patient and radiographic characteristics were similar between the groups (mean age 62y in both, parity; tumor calcification, T2W-intensity), whereas those with e-HRT had significantly lower body weight (68±16kg vs. 77±21kg; p=0.01) and tended to have longer follow-up (6.7±3.9yrs vs. 5.3±3.9yrs; p=0.07). Those with e-HRT had significantly smaller meningiomas (13±6mm vs. 16±9mm at diagnosis and 15±7mm vs. 19±11mm at end of follow-up; p=0.03 for both), and slower absolute grow-rates (0.5±0.8 vs 1.0±2.1mm/year; p=0.05) than those of no-HRT. Proportional growth-rate differences were not significant (3.3%/year vs. 5.4%/year p >0.05). Subgroup analyses showed no difference between vaginal vs. oral/subcutaneous/transdermal route e-HRT vs. no-HRT. PFS defined by RECIST1.1, RANO and clinical (new symptoms or treatment) criteria were 11.1, 6.6 and 14.7years in e-HRT versus 10.5, 5.4 and 11.4years in no-HRT. None of the differences were significant (log-rank p >0.1). CONCLUSIONS In this preliminary analysis, those with e-HRT had smaller tumors that grew slower, suggesting that e-HRT may be safe in incidental meningioma.