LONG-TERM OUTCOMES OF RADIOGRAPHIC AND SYMPTOMATIC CONTROL IN CAVERNOUS SINUS MENINGIOMAS TREATED WITH EXTERNAL BEAM RADIATION THERAPY

Summary: Meningiomas can arise in the cavernous sinus, presenting a significant clinical challenge for effective local control and clincial responses. This study evaluates the efficacy of fractionated stereotactic radiation therapy (fSRT) and fractionated stereotactic radiosurgery (fSRS) in achieving local control and symptomatic relief in patients with benign cavernous sinus meningiomas as first-line therapy. We aim to elucidate and compare the long-term outcomes of these two treatment modalities. We conducted a retrospective analysis of patients diagnosed with cavernous sinus meningiomas at our institution, who underwent fSRT (1.8-2 Gy per fraction) or fSRS (5 fractions). We collected clinical data on tumor characteristics, previous treatments, demographics, radiation dosimetry, treatment response, and survival. Kaplan-Meier curves assessed local control, and chi-squared analysis compared local control rates between the two treatment groups. For the larger fSRT cohort, clinical responses were evaluated at various follow-up intervals (≤36 months, 36-60 months, 60-120 months, 120-180 months, and ≥180 months), calculating frequencies of symptom improvement, stability, and worsening amongst patients with follow-up at these time-points. Our study identified 58 patients treated with fSRT (54 Gy in 1.8 Gy fractions); 43 were included in the analysis after excluding 10 due to inadequate follow-up and 5 due to prior radiation treatment for cavernous sinus meningioma. 10 patients received fSRS with adequate follow-up. The average age across cohorts was 58 (range 21-90), with a Karnofsky Performance Score (KPS) of 90 for both treatment groups. The median follow-up for fSRT cohort and fSRS cohort are 122.2 months and 26.1 months, respectively. The median tumor volume was 9.05 cc for the fSRS cohort (range 0.8-45.7 cc) and 10.5 cc for the fSRT cohort (range 4.9-18.3 cc). Local control rates for the fSRT cohort at 1, 3, 5, and 10 years were 100%, 95.12%, 89.75%, and 89.75%, respectively. The fSRS cohort achieved 100% local control at 1, 3, and 5 years. Chi-squared analysis revealed no statistically significant difference in local control between the two treatment modalities (χ²= 0.758, p= 0.384). Clinical responses for the fSRT cohort showed symptom improvement frequencies of 67.5%, 56.7%, 68%, 69.2%, and 66.7% at the respective follow-up intervals, with stability rates of 25%, 36.7%, 28%, and 23.1%, and 33.3% and worsening symptoms at rates of 7.5%, 6.7%, 4%, and 7.6%. Both fSRT and fSRS demonstrate effective local control and symptomatic relief for cavernous sinus meningiomas. Our findings indicate no significant difference in local control rates between the two therapies, likely due to limited patient numbers in the fSRS cohort. Notably, failures in local control were found to occur within 5 years post-treatment, and over half of the fSRT patients experienced sustained clinical improvement for more than 15 years. These results underscore the importance of long-term follow-up in this patient population. Shray Jain (he/him/his), BS, MS (Presenting Author) - Drexel University College of Medicine; Nilanjan Haldar (he/him/his), MD (Co-Author) - Thomas Jefferson University Hospital Department of Radiation Oncology; Lauren Holt, BA (Co-Author) - Drexel University College of Medicine; Gregory Alexander, MD (Co-Author) - Thomas Jefferson University Hospital Department of Radiation Oncology; Wenyin Shi (he/him/his), MD, PhD (Co-Author) - Thomas Jefferson University Hospital Department of Radiation Oncology