Lower mortality from nasopharyngeal cancer in the Netherlands since 1970 with differential incidence trends in histopathology

Objective: Nasopharyngeal carcinoma (NPC) is rare in western countries albeit affected by common and unrelated phenomena: smoking less in men, more in women and immigration from China and North Africa. We studied trends in NPC incidence, tumour morphology, survival and mortality in order to assess progress against this cancer. Materials and methods: A trend analysis was performed with nationwide incidence and survival data (from The Netherlands Cancer registry in 1989-2009), followed by analysis of mortality (data from Statistics Netherlands) covering the period 1970-2009, and calculating estimated percentages of change (EAPC) in both. According to the WHO classification we distinguished keratinizing SCC (WHO-I), differentiated (WHO-IIA) and undifferentiated (WHO-IIB) non-keratinizing carcinoma. Results: NPC incidence significantly decreased since 1989, especially in males (EAPC 1989-2009: -1.3; 95% CI: -2.5, -0.2) and in patients with keratinizing SCC (WHO-I) (EAPC: -3.6; 95% CI: -5.3, -1.8). By contrast, the incidence of differentiated non-keratinizing tumours (WHO-IIA) significantly increased in the same period (EAPC: 9.6; 95% CI: 5.6, 13.5). One- and three-year relative survival, as an indicator of disease-specific survival increased slightly from 79% to 81% and from 57% to 65% since 1989. NPC mortality significantly decreased since 1970 (EAPC: -1.2; 95% CI: -1.8, -0.5) and more pronounced since 1989 (EAPC: -3.0; 95% CI: -4.3, -1.6). Conclusion: During the past two decades, the incidence of NPC in The Netherlands decreased mainly by less keratinizing, supposedly smoking-related NPC (WHO-I). However, the incidence of non-keratinizing NPC (WHO-IIA, B) increased, most likely due to EBV infection and thus related to higher immigration levels of people from high-incidence areas.