Basal cell adenocarcinoma of the parotid gland: prognostic factors and survival outcomes: a systematic review and pooled patient-level analysis

BACKGROUND: Basal cell adenocarcinoma (BCAC) of the parotid gland is a rare low-grade malignancy with generally favorable prognosis but potential for late recurrence. This systematic review aimed to evaluate survival outcomes and prognostic factors in patients with parotid BCAC. METHODS: A PRISMA-compliant systematic review was conducted using Embase, PubMed, Scopus, and Cochrane Library (1990-2025). Case reports and case series providing individual patient data were included. A pooled patient-level analysis assessed local, regional, and distant disease control, as well as disease-free (DFS), disease-specific (DSS), and overall survival (OS). RESULTS: Twenty-three studies including 68 patients were analyzed. The mean age at diagnosis was 58.6 years. The 5-year DFS, DSS, and OS were 84.1%, 92.7%, and 88.3%, respectively. Overall recurrence occurred in 31% of cases, mainly at the primary site. The absence of adjuvant therapy and perineural invasion were significantly associated with reduced DFS. Positive surgical margins were associated with worse DSS, while facial nerve palsy at presentation associated with decreased OS. Advanced tumor stage showed a trend toward poorer outcomes. Late recurrences and distant metastases have been reported in the literature beyond 5 years of follow-up. CONCLUSIONS: Parotid BCAC generally demonstrates favorable survival; however, adverse pathological features negatively impact prognosis. Adjuvant radiotherapy may improve outcomes in high-risk patients. Prolonged follow-up beyond the conventional 5-year period may be considered, particularly in high-risk patients.