Objective: It has become clear through epidemiological analysis that the incidence of cancers of the lung, liver, colon, and rectum are increasing in Japan every year. However, there have been few epidemiological analyses of nasopharyngeal carcinoma (NPC) in Japan. The aim of this study was to analyze the epidemiology and current incidence of NPC in the Chubu region of Japan during the period from 1996 to 2005.
Methods: Takeshita et al. conducted a similar investigation in the Chubu region 10 years ago, and, as a result, this is a comparative study. The Chubu region is the central region of Japanese main island. We researched NPC patients treated in hospitals in each prefecture over a 10-year period (1996-2005) using a questionnaire.
Results: A total of 525 cases (male:385, female:134, unknown:6) were analyzed epidemiologically, histologically, serologically, and clinically in this study. The incidence per 10(5) population per year was 0.29. For the period of 1986-1995, the age-standardized incidence of NPC was 0.28 per 10(5) persons per year in Takeshita's report. There was no significant difference between the two periods. The ages of the patients ranged from 13 to 90 years. The mean age of was 55.2 years. On the basis of the World Health Organization (WHO) histological criteria, 36% of the patients were classified as WHO I, 27% as WHO II, and 37% as WHO III. Carcinoma was located in the posterosuperior region in 56%, lateral in 41%, and inferior in 3%. Tumor staging showed that 6% to belonged to stage I, 25% to stage II, 31% to stage III, and 38% to stage IV. A neck mass was present in 52% of the patients, ear symptoms in 48%, nasal symptoms in 27%, headaches in 10%, pharyngeal symptoms in 9%, ophthalmologic symptoms in 9%, and cranial neurological symptoms in 9%. The positive rates of serum titers of the antibodies to Epstein-Barr virus (EBV)-related antigens were calculated. The positive rate of anti-EBV-viral capsid antigen (VCA) immunoglobulin (Ig) G titers was 58.6%, that of anti-EBV-VCA IgA titers was 53.6%, and that of EBNA was 81%. The five-year survival rate for all patients was 67.6%, and that for those in stage I, II, III, and IV was 75%, 84%, 69%, and 53%, respectively. The five-year survival rate for stage IV was significantly lower than those for the other stages (P<0.05).
Conclusion: The age-standardized annual incidence of NPC in our survey was 0.29 per 10(5) persons per year, being relatively low and stable.
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