The influence of carmustine wafer implantation on tumor bed cysts and peritumoral brain edema

• We report changes in imaging findings after carmustine wafer implantation for glioma.
• We found 25% of patients exhibited enlargement of the tumor bed cyst by greater than 200%.
• The enlargement occurred especially in patients without a ventricular opening.
• We noted marked perifocal edema in patients with anaplastic oligodendroglioma.

The development of perifocal edema and tumor bed cyst has been reported after implantation of biodegradable carmustine wafers for the treatment of malignant gliomas. We retrospectively evaluated these changes in a series of patients; 19 consecutive patients with malignant glioma who received carmustine wafer implantation at our hospital from January 2013 through July 2013, and 28 patients who underwent surgery prior to our institution’s initiation of carmustine wafer implantation, as historical controls. The volume of the tumor bed cyst and perifocal edema was calculated on MRI acquired at four time points: ⩽72 hours after surgery for baseline, and at 1–4, 5–8, and 9–12 weeks after surgery. The volume of the tumor bed cyst in the wafer group increased significantly relative to the control group at all time points (p = 0.04). Opening of the ventricle was inversely correlated with enlargement of the tumor bed cyst in the wafer group (p = 0.04). The change in the volume of perifocal edema in the wafer group was not significantly different (p = 0.48), but exhibited a considerable increase in patients with anaplastic oligodendroglioma relative to glioblastoma patients in the wafer group (p = 0.01). We demonstrated significant enlargement of the tumor bed cyst volume after carmustine wafer implantation, as well as the development of marked perifocal edema in patients with anaplastic oligodendroglioma.