Population surveys on the prevalence of thyroid cancer in a non-endemic region, Nagano, Japan.

Abstract

AbstractFor the purpose of evaluating the epidemiological situation of thyroid cancer in non‐endemic regions, the prevalence of thyroid cancer was studied in the general population in 15 areas of Nagano Prefecture, Japan.In the survey, 59,106 subjects (representing 80.9% of the population) were examined for goiter. The total number of thyroid diseases detected was 2,098; i.e., 3.5% (1.4% for males and 5.4% for females) of the subjects examined. Non‐endemic diseases were prevalent. Of the cases detected, 633 were diagnosed as nodular goiter, with 472 cases requiring surgical treatment. Of these, operations were performed in 390 cases, while two cases of thyroid cancer were considered too advanced for surgery.In the clinical and histological studies, 76 cases (16 males and 60 females) were diagnosed as having thyroid cancer. Most of the cancer cases detected in the survey consisted of papillary adenocarcinoma. The prevalence rate of thyroid cancer was 1.3 (0.6 for males and 1.9 for females) per 1,000 examined. The prevalence for females varied with area, though this variation was not significant in the case of males. The prevalence by age varied for both sexes, being greater in the thirties and above than in the under‐thirties.It may be stated that the prevalence of thyroid cancer in the general population is as high as one per 1,000 subjects examined in non‐endemic regions, and that this is not merely a non‐representative case, but that a similarly high prevalence of thyroid cancer can be found in other non‐endemic regions.Statistical comparison of the prevalence of thyroid cancer with its mortality or morbidity rate indicates a considerable difference between the two. The incidence of the latter was only approximately one hundredth of the former. Because of this low mortality, thyroid cancer is apt to be neglected, both clinically and epidemiologically, in comparison to other sites of cancer associated with a higher mortality rate.