Rising incidence of adenocarcinoma of the lung in Canada

Abstract

Background/aims: This study examines temporal trends in incidence of lung cancer in 1972-2007, temporal trends in histological types of lung cancer in 1988-2007, and age-period-cohort effects on the incidence rates of lung cancer in Canada.

Methods: Using incidence data for 1972-2007, we calculated the three-year period rates and annual percentage change (APC): from 1988 to 2007 we were able to do this by histological types. We used age-period-cohort modelling to estimate underlying effects on the observed trends in incidence of adenocarcinoma of the lung.

Results: In Canada, age-adjusted incidence rates have increased by 263% in women and 4% in men from 1972 to 2007. Annual percent change in age-adjusted rates for women by histological type from 1988 to 2007 were 2.2% for adenocarcinoma, -0.9% for squamous cell carcinoma and -0.4% for small cell carcinoma. Age-adjusted rates decreased for men over the same 20 years: adenocarcinoma (APC: -0.6%), squamous cell carcinoma (APC: -4.2%) and small cell carcinoma (APC: -3.2%) in men. Age-specific incidence rates increased most rapidly for adenocarcinoma in those aged 75+ years (APC: women 4.3%; APC: men 1.1%). The age-period-cohort modelling suggested that the risk of being diagnosed with adenocarcinoma is decreasing in men and will be decreasing slowly in women.

Conclusions: The adenocarcinoma incidence trends observed are consistent with smoking trends, however, the relative risk with smoking is lower for adenocarcinoma than for squamous cell carcinoma and small cell carcinoma. This suggests that other exposures may play a role in adenocarcinoma incidence, such as exposure to environmental carcinogens.