Salivary duct carcinoma: a Danish national study

BACKGROUND: To present the first national series of salivary duct carcinoma patients, including survival rates and an analysis of prognostic factors.

METHODS: By merging three Danish nationwide registries that encompass an entire population, 34 patients diagnosed with salivary duct carcinoma from 1990 to 2005 were identified. Histological slides were reviewed, and data concerning demographics, tumour site, clinical stage, treatment profiles and follow-up were retrieved. Survival estimates and prognostic factors were evaluated by comparing Kaplan-Meier plots using the Mantel-Haenszel log-rank test.

RESULTS: Salivary duct carcinoma showed an incidence of 0.04/100.000 inhabitants/year. Distant recurrence was seen in 52% of patients. Five-year overall survival, disease-specific survival and recurrence-free survival were 32%, 42% and 35%, respectively. Univariate analyses suggested that overall stage (III/IV) and vascular invasion have a negative impact on all survival measures. Involved resection margins correlated with a poorer overall survival and disease-specific survival, whereas adjuvant radiotherapy improved overall survival and recurrence-free survival.

CONCLUSIONS: Salivary duct carcinoma incidence averages to two episodes per year in the entire Kingdom of Denmark. With half of patients in this study experiencing distant recurrences and only a third surviving at 5 years, prognosis is dismal. Advanced overall stage, vascular invasion and involved resection margins all seem to correlate with a poorer survival, while adjuvant radiotherapy significantly improved outcome. Extensive T-site surgery, neck dissection and adjuvant radiotherapy are therefore recommended.