胃癌の時代的変遷―疫学の立場から

Descriptive Epidemiology of Gastric Cancer in Japan

要旨　わが国の胃癌の年次動向について述べた．胃癌年齢調整死亡率は1960年以降一貫して減少した．年齢調整罹患率も，全国値推計が始まった1975年以降一貫して減少した．1970年代の後半から年齢調整罹患率と死亡率の年次推移に乖離が観察された．胃癌罹患率は，同じ年齢階級でも最近生まれの者ほど減少していた．Laurenのintestinal typeの胃癌年齢調整罹患率が減少傾向を示し，diffuse typeは横ばいと報告されていた．大阪府がん登録によれば，胃癌の5年相対生存率は28％（1975～1977年診断）から49％（1993～1995年診断）へと向上した．生存率の向上には，早期診断の進歩と，“限局”と“領域”患者に対する治療法の進歩が寄与したが，1980年代以降は早期診断の普及への依存が大きかった．内視鏡切除を含む手術割合は，最近10年では75％前後で一定であったが，化学療法の実施割合は減少した．

　Time-trends of gastric cancer, incidence, survival and mortality in Japan were described. The age-adjusted mortality rate has decreased since 1960. The age-standardized incidence rate has also decreased since 1975, when estimates of cancer incidence for all Japan were first started. Dissociation between mortality and incidence curves began to appear since the late 1970s. The age-specific incidence has decreased more markedly in the later birth-cohorts. The age-adjusted incidence was reported to have decreased for the Lauren intestinal type, while it has been constant for the diffuse type. Osaka Cancer Registry data indicated that the relative 5-year survival was 28 ％ for gastric cancer patients diagnosed in 1975-1977, and increased to 49 ％ for those diagnosed in 1993-1995. Improvement in survival was ascribed to early diagnosis of gastric cancer and advanced treatments for the localized and the regional stages. However, early diagnosis seems to have become a greater contributary factor since the 1980s. The proportion of surgery including endoscopic procedures has been around 75 ％ during the last 10 years, while chemotherapy has decreased remarkably.