International trends in lung cancer incidence by histological subtype: adenocarcinoma stabilizing in men but still increasing in women.

OBJECTIVES Trends in overall lung cancer incidence in different countries reflect the maturity of the smoking epidemic. Further understanding of the underlying causes for trends over time can be gained by assessing the trends by sex and histological subtype. We provide a temporal analysis of lung cancer incidence in 12 populations (11 countries), with a focus on cohort-specific trends for the main histological subtypes (squamous cell carcinomas (SCC), adenocarcinomas (AdC), and small cell carcinoma). MATERIAL AND METHODS We restrict the analysis to population-based registry data of sufficient quality to provide meaningful interpretation, using data in Europe, North America and Oceania, extracted from successive Cancer Incidence in Five Continents Volumes. Poorly specified morphologies were reallocated to a specified grouping on a population, 5-year period and age group basis. RESULTS In men, lung cancer rates have been declining overall and by subtype, since the beginning of the study period, except for AdC. AdC incidence rates have risen and surpassed those of SCC (historically the most frequent subtype) in the majority of these populations, but started to stabilize during the mid-1980s in North America, Australia and Iceland. In women, AdC has been historically the most frequent subtype and rates continue to increase in most populations studied. Early signs of a decline in AdC can however be observed in Canada, Denmark and Australia among very recent female cohorts, born after 1950. CONCLUSIONS The continuing rise in lung cancer among women in many countries reinforces the need for targeted smoking cessation efforts alongside preventive actions.