Space-occupying cyst development in the resection cavity of malignant gliomas following Gliadel® implantation--incidence, therapeutic strategies, and outcome.

Gliadel® (Eisai Inc., Woodcliff Lake, NJ, USA) is the only therapeutic agent approved by the Food and Drug Administration and the European Medicines Agency for local chemotherapy of malignant gliomas. With increasing use of this treatment, characteristic side effects have become evident. While most side effects can be managed conservatively, cyst formation requires further intervention. From 2004 to 2009 at our institution 88 patients with malignant gliomas were treated with Gliadel®. Ten patients (11%) developed a space-occupying cyst in the resection cavity, seven of which caused clinical symptoms of mass effect that was most prominent 2 weeks after Gliadel® implantation (median=16, range=9-30). Despite dexamethasone treatment symptoms progressed, necessitating various surgical interventions. In four patients the cysts were drained percutaneously through a burrhole using a 19-gauge needle. If puncture was not possible (three patients) or not sufficient (two patients), an Ommaya reservoir was implanted for repetitive drainage. In two patients this treatment was combined with open decompression of the cyst. On average, cysts were drained three times. Eventually the symptoms subsided, corresponding to shrinkage of the cysts as shown on follow-up imaging. We describe a serious side effect of local chemotherapy, which may cause rapid clinical deterioration and require direct intervention. While reservoir implantation apparently represents a more elegant treatment option, our experience shows that draining the cyst, even only a few times, sufficiently ameliorates the symptoms and subsequently reverses and halts further cyst enlargement.