Epidemiological research into nasopharyngeal carcinoma in the Chubu region of Japan

Although patient death due to nasopharyngeal carcinoma (NPC) is increasing, few epidemiological analyses of NPC in Japan have been conducted since Sawaki’s report in 1979. To determine the current incidence of NPC in Japan we examined NPC case in the Chubu area from 1986 to 1995. The leaders and reporting representatives of all otorhinolaryngological groups in the area were asked for their support of this epidemiological research. A total of 607 cases (445 male and 162 female NPC patients) were analyzed epidemiologically, histologically, serologically and clinically in this study. The incidence of NPC gradually increased with age. The mean age of the patients was 54.1 years. The age-standardized annual incidence in the Chubu region was 0.28 per 105 persons per year. The incidence in prefectures bordering Japan Sea (0.36) was significantly higher than that of prefectures facing the Pacific Ocean (0.21, P<0.05). On the basis of World Health Organization (WHO) histological criteria, 12% of the cases were classified as WHO I, 54% as WHO II and 34% as WHO III. As for tumor origin, in 58% of the cases it originated posterosuperiorly, in 32% laterally and in 1% inferiorly. Tumor staging showed 4% to belong to stage I, 9% to stage II, 15% to stage III and 72% to stage IV. The positive rates of serum titers of the antibodies to Epstein–Barr virus (EBV) related antigens were calculated according to WHO histological criteria. The positive rate of anti-EBV-viral capsid antigen (VCA) immunoglobulin (Ig) G titers was 43% for WHO I, 62% for WHO II and 70% for WHO III, with significant difference between the rates for WHO I and for WHO II or III (P<0.05). The positive rate of anti-EBV-VCA IgA titers was 58% for WHO I, 67% for WHO II, and 81% for WHO III, with a significant difference between the rates for WHO I and for WHO III (P<0.05). The NPC patients showed otological symptoms (48%), nasal symptoms (35%), pharyngeal symptoms (14%), ophthalmologic symptoms (5%), cranial neurological symptoms (18%), headaches (14%) and cervical lymph node swelling (70%). They also suffered from lung metastasis (20%), liver metastasis (10%), kidney metastasis (0.4%), brain metastasis (4%), thyroid metastasis (0.4%) and bone metastasis (20%). The cause of death of NPC patients was intracranial invasion (30%), organ metastasis (41%), lymph node metastasis (13%) and other reasons (14%).