Nasopharyngeal squamous cell carcinoma: A comparative analysis of keratinizing and nonkeratinizing subtypes

Background: Nasopharyngeal squamous cell carcinoma (NPSCC) is uncommon in non-endemic regions. Two major histologic subtypes are recognized: keratinizing (K-NPSCC) and nonkeratinizing (NK-NPSCC). We hypothesize that significant differences exist between the 2 in terms of demographic, clinicopathologic, survival, and prognostic features. We aim to show that differentiating between the 2 subtypes is perhaps the most important first step at the time of diagnosis. Methods: Using a retrospective cohort design, the U.S. National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registry was used to extract data on the 2 major subtypes of NPSCC. Frequency, incidence, and relative survival (RS) were analyzed comparatively. Regression analysis was conducted and hazard ratios (HRs) calculated. Results: A total of 1624 cases were identified: 1234 (76.0%) cases of NK-NPSCC and 390 (24.0%) cases of K-NPSCC. Five-year RS was 60.6% for NK-NPSCC and 40.5% for K-NPSCC. Regression analysis revealed K-NPSCC to be a poor prognostic factor (HR 2.1; 95% confidence interval, 1.8-2.6; p < 0.0001). Other factors associated with a poor prognosis included female gender in K-NPSCC, age greater than 44 years in both groups, and advanced-stage disease at diagnosis. Favorable prognostic factors included Asian/Pacific Islander race, and treatment with radiation therapy. Higher histologic grade did not portend a worse prognosis for either group. Conclusion: NPSCC remains an uncommon malignancy in the United States. K-NPSCC and NK-NPSCC represent 2 different histologic entities with important clinical differences. K-NPSCC carries a worse overall prognosis when compared to NK-NPSCC.