Adenoid cystic carcinoma brain metastases treated with stereotactic radiosurgery: A single institution retrospective cohort study and comprehensive literature review.

Abstract

Adenoid cystic carcinoma (ACC) is a malignant neoplasm arising from the minor and major salivary glands that tend to spread by perivascular and perineural routes. Brain metastases (BM) secondary to ACC are extremely rare, and the standard management strategy has not been well reported due to the rarity. Notably, no previous study has specifically examined the efficacy of stereotactic radiosurgery (SRS) for BM from ACC. We retrospectively reviewed cases of BM from ACC treated with CyberKnife (CK) SRS at our institution between 1998 and 2024. A total of 40 lesions from 5 patients were included. Tumor control was defined based on radiological response to CK SRS as a complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD) per response evaluation criteria in solid tumors (RECIST) guidelines. The median Follow-up duration was 11 months (Range: 3-51 months). The median age at treatment was 52 years with a male-to-female ration of 3:2. The median maximum diameter of the lesions was 7.mm. The median prescription dose delivered was 24 Gy. The treatment responses at the first follow-up were CR/PR/SD/PD: 9/19/12/0. At the last follow-up, 5 lesions had local progression, with one lesion at 39 months, and 4 lesions at 11 months after CK SRS, while 16 lesions remained CR. The cumulative 3-months, 6-months, and 12-months local control rates were 100%, 100%, and 89%, respectively. To date, this is the largest study examining the efficacy of SRS for ACC BM. Our results showed sufficient local control following the treatment.