Tumor bed cyst formation after BCNU wafer implantation: report of two cases

Interstitial implantation of BCNU wafers is currently used to treat glioblastoma multiforme. Known complications of BCNU wafer implantation include abnormalities of wound healing (including CSF leak), edema formation, and intracranial infection. The purpose of this report is to alert neurosurgeons to an additional potential side effect: formation of a cystic mass within the implanted tumor bed.

Two patients are described: a 54-year-old male, who presented with a large right parieto-occipital mass, and a 47-year-old woman with a large right frontal lobe tumor. Both tumors were found on initial craniotomy to be glioblastoma multiforme; both recurred rapidly despite radiation therapy. Patients were treated with a second craniotomy for tumor resection and placement of BCNU wafers. After implantation, the first patient did well for 6 weeks, then developed lethargy, headaches, and vomiting. CT scan showed a large cyst at the craniotomy site; this required reoperation for drainage. The second patient had a seizure, deterioration of mental status, and progressive hemiparesis 10 days after wafer implantation. CT scan again showed that a large cyst had formed in the area of the previous surgery; she also required reoperation. In each case, minimal tumor and no evidence of infection were found. Within a few more weeks, each patient succumbed to progressive disease.

The hypodense, roughly spherical cysts clearly demonstrated clinically significant mass effect, and required reoperation despite treatment with high-dose corticosteroids. Neurosurgeons should be alert to the possibility of tumor bed cyst formation in patients treated with interstitial BCNU wafers.