A comparison of trends in the incidence rate of lung cancer by histological type in the Osaka Cancer Registry, Japan and in the Surveillance, Epidemiology and End Results Program, USA.

Trends in the incidence rate of lung cancer by histological type were examined, based on data from the Osaka Cancer Registry (OCR), Japan and the Surveillance, Epidemiology and End Results Program (SEER), USA. Among males, an increasing trend was observed for adenocarcinoma in both registries. In the OCR, the incidence rate of adenocarcinoma has recently overtaken that of squamous cell carcinoma, whereas in the SEER, adenocarcinoma had already taken the lead since 1990-93. For squamous cell carcinoma, the decreasing trends in the OCR were consistent with a previous study, whereas in the SEER, the decline was earlier and steeper. For small cell carcinoma, the incidence rate was leveling off in the OCR, whereas it was already in decline in the SEER. For large cell carcinoma, the decreasing trend began earlier in the SEER. Among females in both registries, the incidence rate of adenocaricinoma has clearly been on the increase, whereas in other histological types the incidence rates were decreasing or at least leveling off. As for the age-specific incidence rate, different patterns were observed between the two registries: in the OCR, the incidence rate was on the increase in older age groups such as 70-74 years and also in younger age groups such as 45-49 years, whereas it decreased in intermediate age groups such as 55-59. In contrast, stable decreasing trends were observed in the SEER, except for adenocarcinoma. The increase in incidence rate observed among younger age groups in the OCR should be carefully monitored.