Survival rates and prognostic factors for infiltrating salivary duct carcinoma: Analysis of 228 cases from the Surveillance, Epidemiology, and End Results database

Abstract

Background: The survival rates and prognostic factors for salivary duct carcinoma (SDC) are not clear.

Methods: Survival estimates and prognostic factors were evaluated for 228 patients with SDC identified from the Surveillance, Epidemiology, and End Results (SEER) database.

Results: Median overall survival (OS) duration for patients with SDC was 79 months and 5-year disease-specific survival (DSS) rate was 64%. Among patients with SDC with lymph node involvement, larger primary tumor size (>3 cm) was associated with twice the risk of death (p < .03). Factors predictive of improved DSS were age (p = .01), tumor size (p = .006), tumor grade (p = .02), and lymph node involvement (p < .001). Adjuvant radiotherapy did not improve survival when compared to surgery alone for early-stage (I-II) disease (p = .28).

Conclusion: Younger patients with SDC (<50 years) showed a better prognosis. Primary tumor size and lymph node involvement were independent and additive risk factors for poor prognosis. The role of adjuvant radiotherapy in the treatment of SDC needs to be explored further.

Keywords: SEER; prognostic factors; radiation; salivary duct carcinoma; survival rates.

FIGURE 1

Relationship between tumor size, tumor grade, and lymph node involvement. (A) Relationship between the size of the primary tumor and lymph node involvement (based on 193 patients). Statistically significant linear trend (p for trend, < .001). (B) Relationship between the tumor grade and lymph node involvement (based on 148 patients). Statistically significant linear trend (p for trend, < .001). LN, lymph node. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIGURE 2

Comparison of disease-specific survival (DSS) by patient age, primary tumor size, and lymph node involvement. (A) Comparing patients <50 and >50 years of age (hazard ratio [HR], 2.91; 95% confidence interval [CI], 1.14–7.40*; p = .03). (B) Comparing patients with and without lymph node involvement (HR, 2.43; 95% CI, 1.35–4.39*; p = .003). (C) Comparing patients with tumor size of <3 cm and >3 cm (HR, 1.86; 95% CI, 1.05–3.30*; p = .03). (D) Comparing tumor size of <3 cm and >3 cm among patients with lymph node involvement (HR, 2.15; 95% CI, 1.08–4.30*; p = .03). *HR calculated based on Cox regression model after adjusting for age, sex, race, cancer site, and treatment type. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIGURE 3

Disease-specific survival (DSS) comparing the surgery only group to the adjuvant radiation group stratified by stage. (A) Comparing the surgery only group to the adjuvant radiation group among patients with stage I and II disease (hazard ratio [HR], 1.82; 95% confidence interval [CI], 0.58–5.74*; p = .31). (B) Comparing the surgery only group to the adjuvant radiation group among patients with stage III disease (HR, 0.65; 95% CI, 0.12–3.50*; p = .61). (C) Comparing the surgery only group to the adjuvant radiation group among patients with stage IV disease (HR, 0.70; 95% CI, 0.26–1.89*; p = .48). *Hazard ratio calculated based on Cox regression model after adjusting for age, sex, race, and anatomic site. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]