Radiation Induced Sarcomas of the Skull Base: Two Unique Cases and a Literature Review

Objectives: Radiation induced sarcomas of the skull base are extremely rare with only a handful of cases reported in the literature, the vast majority of which are found following radiation to pituitary adenomas. Here, we report two unique cases of radiation induced skull base sarcomas. The first is a fibrosarcoma of the skull base following resection and radiation of an esthesioneuroblastoma and the second is a skull base pleomorphic sarcoma following radiation of a peripheral neural-ectodermal tumor (PNET). We describe the presentation, histology, radiology, treatment, outcomes, and review the literature.

Methods: Case reports and review of the literature.

Case Reports: Case 1: A 59 year-old female presented with frontal headaches and fatigue four and a half years following resection and adjuvant chemoradiation of a Kadish stage C-Hyams grade II/IV esthesioneuroblastoma. An MRI revealed breakdown of her prior pericranial flap and a left frontal lobe pneumatocele with no discernable mass. One year later, she represented with proptosis and continued headaches. An enhancing lesion in the right ethmoid cavity extending into the right orbit and along the anterior cranial fossa was seen on MRI. Endoscopic biopsy was consistent with fibrosarcoma. She underwent a bifrontal craniotomy, right orbital exenteration, craniofacial resection with ethmoidectomy and sphenoidotomy, and radial forearm free flap reconstruction. Pathology revealed a grade 3/3 adult-type fibrosarcoma with invasion into the bone and positive margins. Her course was complicated by a wound dehiscence, but she is otherwise doing well 4 months post-operatively. She will likely undergo further radiation therapy once she has fully healed. Case 2: A 40 year-old male presented with headache, diplopia, epistaxis, and CSF leak complicated by meningitis twenty-four years following initial chemoradiation for a multiply recurrent sinonasal PNET that was subsequently treated with craniofacial resection and repeat radiation to the skull base. CT/MRI revealed a nasopharyngeal mass invading the clivus and anterior skull base. An endoscopic biopsy was positive for a high-grade sarcoma with fibroblastic and myofibroblastic differentiation. He underwent an anterior cranial facial resection, right medial maxillectomy, right selective neck dissection, and anterolateral thigh flap reconstruction. Final pathology was consistent with high-grade pleomorphic sarcoma. His course was complicated by pneumocephalous, CSF leak, meningo-ventriculitis, recurrent skull base osteomyelitis, a large left frontoparietal and right frontal stroke, and tumor recurrence. He passed away 17 months following diagnosis of his sarcoma.

Conclusions: Radiation-induced skull base sarcomas pose a significant risk to patients successfully treated with radiation alone or as part of a multimodal treatment and have an especially poor prognosis. While these tumors have been little reported in the literature, and of those reported are predominantly seen following treatment of pituitary adenomas, it is important to recognize their occurrence in all tumors receiving radiation to the skull base. As long-term cancer survival improves, this will be an increasingly important part of long-term follow up.