Epidemiology of nasopharyngeal carcinoma (NPC) in California: Survival advantage of Chinese WHO Type 1 NPC patients resulted in Asian ethnicity as an independent and favorable prognostic factor of survival for NPC patients as a whole and for patients with the WHO histologic type 1

Abstract

5514 Background: We have previously shown that Chinese race is an independent and favorable prognostic factor in NPC survival. We expanded our study to investigate whether Asian ethnicity has the same favorable survival characteristics and if there is a survival difference between Chinese and non-Chinese Asians. Methods: 1,657 newly diagnosed NPC patients from 1992 to 2002 were analysed from the population-based California Cancer Registry. Five year survival rate estimates and Kaplan-Meier curves were calculated. Cox proportional ratios were used to identify independent prognostic factor for survival. Results: The 5-year survival rate of Asian NPC patients was improved compared to non-Asian patients (62% vs 47%; P < .0001). By multivariate analyses, early age of diagnosis, localized stage at presentation (vs distant, HR = 0.41; P < .0001), WHO Type 3 histology (vs Type 1; HR = 0.64; P < .0001), socio-economic status (highest vs lowest quartile; HR = 0.71; P = .0012), use of radiation (vs none; HR = 0.55; P < .0001), and Asian ethnicity (vs Caucasian; HR = 0.82; P = .016) were associated with improved survival. Chinese composed the majority of the Asian ethnicity (49.1%) followed by Filipino (21.2%) and Vietnamese (14.9%). The 5-year survival rate of Chinese was better than non-Chinese Asians (67% vs 56%; P = .0005). When Asian ethnicity was analyzed separately as Chinese and non-Chinese, Chinese retained an overall favorable prognosis (HR = 0.72; P = .0016) whereas non-Chinese Asians did not (HR = 0.91; P = .34). Within each NPC WHO histologic type, early age of diagnosis, localized stage at presentation, and use of radiation were favorable prognostic factors. Chinese (HR = 0.62; P = .0006) but not non-Chinese Asian ethnicity (HR = 0.78; P = .053) was an additional favorable prognostic factor within WHO histologic Type 1. Conclusions: The significant survival advantage of Chinese WHO Type 1 NPC patients resulted in Asian ethnicity being an independent and favorable prognostic factor for survival in NPC. This observation may reflect underlying genetic difference among different racial groups with NPC WHO Type 1. No significant financial relationships to disclose.