Therapy options in the management of endolymphatic sac tumors: A case series and literature review.

Background: Endolymphatic sac tumors (ELSTs) are rare, yet highly destructive tumors of the petrous bone associated with significant neurological impairment, such as hearing loss and facial weakness. Surgical intervention is the most common initial management strategy for ELST; however, marred by the risk of recurrence and burden of neurologically significant locoregional structures, radiation-based options provide an alternative strategy in the management of ELST recurrence. In 2018, one of the authors presented a case of recurrent ELST managed with salvage gamma knife radiosurgery. Here, we describe three further cases that were managed with different radiotherapeutic methods. Case Description: We report three separate cases of histologically confirmed ELST in a 71-year-old female, a 26-year-old male, and a 74-year-old female, respectively. Each case presented with a variety of chronic-onset neuro-otological symptoms. For each patient, a primary neurosurgical approach was opted for, with radiotherapy arranged in adjuvant or salvage/relapse settings following multidisciplinary team discussion. We explore the considerations for each case and discuss the role of radiation in this insidious pathology. Conclusion: This case series adds to the emerging literature by further highlighting the role of radiation as both an adjunct following neurosurgical intervention and a salvage procedure in those patients in which conventional upfront, or "re-do" surgery is not an option. As reported by other groups, different radiotherapy modalities can be considered, including stereotactic radiosurgery and volumetric modulated arc therapy radiation, though with variable results. However, due to the small number of cases so far reported, further data compilation is warranted to define the role of radiotherapy in the management of ELST.