Abstract 2280: Burden of lung cancer in Australia avoidable by modifications to lifestyle-related risk factors
Authors: Laaksonen Maarit A. , Arriaga Maria , Hull Peter , Canfell Karen , MacInnis Robert , Banks Emily , Giles Graham , Mitchell Paul , Cumming Robert , Adelstein Barbara-Ann , Byles Julie , Magliano Dianna J. , Shaw Jonathan , Taylor Anne , Price Kay , Hirani Vasant , Vajdic Claire M. 
Published: July 2017

Aim: The cancer burden avoidable through risk factor modification can be quantified using the Population Attributable Fraction (PAF) which combines estimates of the prevalence of the risk factor exposure in the population and the strength of the exposure-cancer association. PAF for risk factors causally related to cancer is most accurately estimated from cohort studies, using analytical approaches that account for death as a competing risk. We provide the first such estimates of the lifestyle-related avoidable lung cancer burden.

Methods: Seven contemporary Australian cohort studies (N = 367,772), with comprehensive data on exposure to lifestyle-related risk factors, were linked to the Australian Cancer Database and National Death Index to identify lung cancers and deaths from any cause. The risk factors were harmonised across the studies and the data pooled. The strength of the exposure-cancer and exposure-death associations were estimated using a proportional hazards model, adjusting for age, sex and the other lifestyle exposures. Age- and sex-specific exposure prevalence was estimated from the Australian National Health Survey 2011-2012. These estimates were then combined to calculate the PAFs and their 95% confidence intervals (CI) using a newly developed method accounting for competing risk of death.

Results: During the first 10-years follow-up, 2,030 incident lung cancers and 20,348 deaths were ascertained as first events. Smoking, physical inactivity and insufficient fruit intake were statistically significantly associated with both lung cancer incidence and death. Most of the lung cancer burden (PAF = 73%, CI = 69-76%) was attributable to current or past smoking, with 31% (CI = 27-35%) of the burden attributable to current smokers. Physical activity below Australian recommendations (&lt; 150 minutes of moderate or 75 minutes of vigorous exercise per week) explained 14% (CI = 6-22%) and fruit intake below Australian recommendations (&lt; 2 daily serves) explained 6% (CI = 0-12%) of the lung cancer burden. Each risk factor contributed more to the lung cancer burden in men than in women. Overall, 78% (CI = 74-81%) of the lung cancer burden was attributable to current or past smoking, physical inactivity and insufficient fruit intake. The combined contribution of modifiable risk factors (i.e. excluding past smoking) was 44% (CI = 37-50%). Based on projected Australian cancer incidence rates, this would translate to 59,000 avoidable lung cancers in the next 10 years.

Conclusions: According to these joint PAF estimates, the current lung cancer burden in Australia could be reduced by up to half in 10 years by quitting smoking and increasing physical activity and fruit intake to the recommended levels. As the combined effect of risk factors is rarely additive, knowing both individual and joint effects of risk factors on cancer burden is essential in planning cancer interventions and public health policies and predicting their potential impact.

Citation Format: Maarit A. Laaksonen, Maria Arriaga, Peter Hull, Karen Canfell, Robert MacInnis, Emily Banks, Graham Giles, Paul Mitchell, Robert Cumming, Barbara-Ann Adelstein, Julie Byles, Dianna J. Magliano, Jonathan Shaw, Anne Taylor, Kay Price, Vasant Hirani, Claire M. Vajdic. Burden of lung cancer in Australia avoidable by modifications to lifestyle-related risk factors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2280. doi:10.1158/1538-7445.AM2017-2280