Rdta-16 Cesium Brachytherapy in Rapidly Progressive Thymic Carcinoma Intracranial Metastatic Disease

Thymic carcinoma is a rare, aggressive cancer with less than 100 cases diagnosed in the U.S. annually. Cerebral metastases are uncommon, occurring in approximately 5% of patients. Our patient is a 65-year-old man that was diagnosed with stage IVB thymic carcinoma, initially with a single metastatic lesion to the brain. He underwent resection of a right parietal mass followed by SRS. Subsequently he developed other lesions and underwent resection of a right frontal mass followed by SRS and resection of a right temporal mass. During imaging for radiation planning for the temporal tumor, he was found to have rapid recurrence of the mass. The patient returned to the operating room for re-resection of his right temporal mass. At the end of the resection, five cesium-containing collagen sponges were placed into the resection cavity. Due to his history of multiple prior radiation treatments, the brachytherapy tile placed along the anterior medial fossa was bumped out with a piece of dural substitute to decrease the dose of radiation to the optic nerve. This provided an additional 5mm of separation between the optic nerve and the radiation seeds. The patient tolerated the procedure well and is doing well at 6 month follow up without local recurrence or new lesion. The dose to his right optic nerve was decreased from 55 Gy to 34 Gy by bumping the radiation source with a layer of dural substitute. His vision remains stable. This case demonstrates that immediate post-operative radiation via Cesium brachytherapy placement can provide a treatment option for patients that will not tolerate a delay due to the rapidly progressive nature of their disease. In addition, this is the first description of a technique to buffer critical structures from toxic doses of radiation by adjusting placement of the radiation source using a dural substitute.