Radiotherapy for recurrent intracranial epidermoid cysts without malignant transformation: a single-institution case series Abstract Introduction Recurrent intracranial epidermoid cysts may be difficult to address surgically given their proximity to critical neurovascular structures of the skull base. There are emerging reports of using radiotherapy (RT) for the treatment of recurrent epidermoid cysts. Here, we report a case series of adjuvant fractionated external beam RT for recurrent intracranial epidermoid cysts. Methods A single-institution review of all recurrent epidermoid cysts treated with adjuvant therapy between 2000 and 2017 was performed. Results Eight patients with recurrent epidermoid cysts who underwent adjuvant external beam RT were identified. Average age at initial diagnosis was 42.2 years, and median clinical follow-up after initial diagnosis and RT was 16.4 and 2.9 years, respectively. The median number of surgical resections prior to RT was 3 (range 2–5). Rationale for RT included multiple recurrent disease, rapid recurrence following prior resection, increased risk of further surgical morbidity, and patient preference. Median dose was 50.4 delivered in 1.8 Gy fractions (median 28 fractions). By the date of last follow-up, no patient has demonstrated progression, and there have been no cases of malignant degeneration. Conclusion Adjuvant RT should be considered in the context of recurrent epidermoid cysts to decrease the likelihood of further recurrences.