Lung cancer in New South Wales: current trends and the influence of age and sex

OBJECTIVE: To examine the effects of time, sex and age at diagnosis on lung cancer incidence rates and the distribution of the histological types of lung cancer in New South Wales. DESIGN AND SETTING: Retrospective analysis of data from the NSW Cancer Registry and Australian Bureau of Statistics population data for NSW for 1985-1995. MAIN OUTCOME MEASURES: Trends in lung cancer incidence rates between 1985 and 1995 for men and women aged over 30 years; changes in incidence rates within age groups; and incidence rates of histological subtypes relative to sex and age. RESULTS: The incidence of lung cancer in men aged 40-80 years fell, while that in women aged over 65 rose. Rates were stable in younger women and older men. Incidence rates in men aged 40-60 years fell by 40%-60%. Were it not for the reduction in incidence rates in men between 1985 and 1995, the number of male lung cancer cases in 1995 would have been greater by 389 (95% CI, 362-415). In women, increasing incidence rates were responsible for an extra 242 cases (95% CI, 232-253) in 1995. Adenocarcinoma comprised a greater percentage of lung cancer cases in younger people, while squamous-cell carcinoma increases steadily with age in both men and women. Women with lung cancer are less likely to have squamous-cell carcinoma (25% for women v. 40% for men) and therefore more likely than men to have adenocarcinoma (35% of new female cases v. 26% for men) or small-cell lung cancer (24% v. 19%). CONCLUSIONS: Increased smoking cessation has seen a halving of lung cancer rates in middle-aged men. Whether this represents delayed or prevented cases is uncertain. The distribution of histological subtypes of lung cancer in women is different from that in men, and it is not clear whether this difference is hormone-dependent or related to historical patterns of smoking.