NIMG-18. EFFECT OF BEVACIZUMAB AGAINST CYSTIC PART OF BRAIN TUMOR

Abstract

Abstract BACKGROUND Bevacizumab improves the symptom via reducing the peritumoral edema and/or normalizing BBB, and occasionally via reducing the tumor size. However, the effect against active cystic portion has not been documented yet. We focused on the effect of bevacizumab on cystic component of brain tumors. MATERIALS AND METHODS Between 2008 and 2018, 139 patients with primary or metastatic brain tumor were treated with bevacizumab in our institution. We defined cystic lesions as high intense lesion of size ≥1 cm on T2-weighted imaging, and excluded necrotizing cysts and cystic changes in surgical resection cavity. The images before and after administration of bevacizumab were examined, and changes in cyst size was evaluated as follows: CR, PR, MR (reduction by ≥25%), SD, PD. The effect of bevacizumab on tumor itself was determined according to RANO criteria. RESULTS Of the 139 patients, 212 (15.1%) had cystic component. Among these 21 tumors, 14 had progressively increasing cysts prior to bevacizumab administration. On the first imaging following administration of bevacizumab, the response of cysts were as follows: CR 2, PR 7, MR 7, SD 5. The best response of cyst to bevacizumab treatment were as follows: CR 6, PR 7, MR 4, SD 4. The group of patients with progressively increasing cysts prior to bevacizumab treatment had significant cyst size reduction compared to stable cyst size groups, at initial image after bevacizumab (mean 62.6% vs. 22.5%, P=0.0055) and at best response timing (mean 76.3% vs. 32.8%, P=0.0050). The effect on the tumor itself was not associated with cyst responses, and the response rate as per RANO was as follows: CR 1, PR 11, SD 9. CONCLUSION Bevacizumab is effective against progressively increasing cysts. Although cyst reduction effect and tumor response are independent, bevacizumab may be effective for patients who are symptomatic due to cystic enlargement.