Carcinoma ex Pleomorphic Adenoma: Multi-Institutional Retrospective Cohort Study.

Objective: Carcinoma ex pleomorphic adenoma (CXPA) is a rare malignancy and survival rates vary throughout literature. The primary objectives are to study overall survival (OS), disease-specific survival (DSS), locoregional recurrence-free survival (LRFS), and secondarily margin status.

Study design: Multi-institutional retrospective cohort study.

Setting: Queen Elizabeth II Health Sciences Center (QEII HSC) from 2006 to 2023 and the University of Michigan (UM) from 2017 to 2023.

Methods: An institutional pathology database (QEII HSC) and parotidectomy database (UM) were used to identify 37 patients with CXPA who underwent surgical resection.

Results: Most cases were locoregionally advanced with 51% being ≥T3 and 32% being cervical node positive. All cases were treated with surgery, 78% received adjuvant radiation. Overall, 2-year survival was 82% and 5-year survival was 61.7%. In univariate analysis, tumor size >4 cm, pathologic nodal stage ≥1, pathologic overall stage 4 disease, lymphovascular invasion, extranodal extension, and positive margins were associated with increased risk of death. In adjusted multivariable analysis, only pathologic nodal stage ≥1 (hazard ratio [HR] 9.474, confidence interval [CI] 1.19-75.41, P = .034) remained statistically significant. The 2-year LRFS was 80% and the 5-year LRFS was 75%. Of the 7 patients with locoregional recurrence, 6 had prior adjuvant radiation, and 4 recurred locally. Multivariable cox models for LRFS were not significant.

Conclusion: Patients with CXPA that metastasize to the neck have a worse prognosis. LRFS after surgery is 75% with high rates of adjuvant radiation. Further research on prognostic factors of LRFS and adjuvant radiation outcomes is required.