Trends in incidence of small cell lung cancer and all lung cancer.

BACKGROUND: The incidence of small cell lung cancer (SCLC) is often quoted as 'around 20%' of all lung cancers but is reportedly decreasing over time. We analysed the trends in incidence of SCLC and compared these with the trends in lung cancer overall among males and females in South East England. METHODS: We identified 237,792 patients diagnosed with lung cancer (ICD-10 C33-C34) between 1970 and 2007. We used a Poisson regression age-cohort model to estimate the age-specific rates in the 1890-1960 birth cohorts. We computed age-standardised incidence rates using the European standard population. In addition, we analysed the trends of lung cancer subtypes according to morphology. RESULTS: In the most recent time period, SCLC accounted for 10% and 11% of cases of all lung cancer among males and females, respectively. Among the morphologically specified lung cancers, SCLC accounted for 15% and 17% among males and females, respectively. There was a decrease of SCLC incidence over time and by birth cohort in both sexes. The decrease in SCLC was more marked than that in all lung cancers. CONCLUSION: The decrease in SCLC incidence rates may reflect decreases in the prevalence of cigarette smoking, and changes in the type of cigarettes smoked.