Clinicogenomic Features and Outcomes of Adenoid Cystic Carcinoma With Central Nervous System Metastases: A Single‐Institution Cohort Study

BACKGROUND: Adenoid cystic carcinoma (ACC) is a rare malignancy with a propensity for perineural invasion and hematogenous spread. Central nervous system (CNS) involvement is uncommon, and detailed clinical and genomic data on this aspect of the disease remain limited. METHODS: We performed a single-institution retrospective cohort study of patients with biopsy-confirmed ACC and CNS involvement treated at the University of Pennsylvania. Clinical features, CNS disease patterns, treatment modalities, molecular alterations, and survival outcomes were abstracted from the electronic medical record. RESULTS: Seventeen patients were identified. CNS involvement occurred a median of 40 months after initial ACC diagnosis. CNS disease included parenchymal metastases, leptomeningeal disease, and patterns suggestive of neurotropic or perineural intracranial extension. Leptomeningeal involvement was present in 6 patients. Targeted next-generation sequencing demonstrated NOTCH1 alterations in 7 patients, with additional recurrent alterations in CREBBP, BAP1, FGFR2, and PI3K-pathway genes. CNS-directed therapy included surgery, stereotactic radiosurgery, hypofractionated radiotherapy, whole-brain radiotherapy, and conventionally fractionated radiotherapy. Median progression-free survival was 5.4 months, and median overall survival was 9.4 months after CNS involvement. CONCLUSIONS: CNS involvement in ACC was associated with poor outcomes despite multimodal therapy. NOTCH1 alterations and leptomeningeal disease were frequent in this cohort, but these findings should be interpreted as hypothesis-generating given the small sample size and absence of a matched non-CNS comparator cohort.