Treatment outcome and prognostic factors analysis of carcinoma ex pleomorphic adenoma of major salivary glands

Background: Carcinoma ex pleomorphic adenoma (CXPA) is an uncommon malignant tumor with aggressive behavior but the treatment outcomes and prognostic factors are rarely reported. Methods: From April 2008 to May 2021, clinical data of 22 patients with pathologically proven CXPA were retrospectively reviewed. Twenty patients received surgery first, followed by adjuvant radiotherapy (n=13), chemoradiotherapy (n=5) and observation (n=2). Definitive chemoradiotherapy without operation was delivered for 2 cases. We analyze treatment outcomes and prognostic factors. Results: After a median follow-up of 46.5 months (range, 13–128 months), we observed 8 relapses (4 distant metastases alone, and 4 combined distant metastases with locoregional recurrence) and 5 deaths (all due to uncontrolled tumor). The 5-year overall survival (OS), progression-free survival (PFS), locoregional-free survival (LRFS) and distant metastasis-free survival (DMFS) were 71.9%, 65.3%, 78.1%, and 61.4%, respectively. Prognostic factor analyses for all 22 patients found 2 potential predictors—tumor origin and clinical N-stage. Combining both factors revealed that patients with submandibular origin plus clinical positive regional nodes had significantly worse OS (5-year rate, 0% vs. 90.0%, P<0.001), PFS (5-year rate, 0% vs. 75.7%, P<0.001), LRFS (5-year rate, 0% vs. 86.8%, P=0.002), and DMFS (5-year rate, 0% vs. 73.5%, P<0.001). Cox univariate analysis confirmed similar findings. Among unfavorable pathological features for 20 patients who received surgery, invasiveness subtype is the only potential factor in predicting PFS (P=0.048) but not significant for OS (P=0.158), LRFS (P=0.185), and DMFS (P=0.071). Conclusions: Our treatment results of 5-year OS 71.9% and PFS 65.3% for CXPA still have room for improvement. This study identifies three potential prognostic factors—tumor origin, clinical N-stage, and pathological invasiveness subtype.