How Many Cancer Cases are Preventable in Israel? Calculating Population Attributable Risks of Cancer with respect to Modifiable Risk Factors

Introduction: The cancer burden in Israel is substantial, with approximately 26,000 newly diagnosed invasive cancer cases and 11,000 cancer deaths occurring in 2015. Many cancer types are causally associated with preventable or at least modifiable risk factors, such as cigarette smoking, excess body weight, physical inactivity and others. Estimating the population attributable fraction (PAF) of selected cancer types with respect to certain associated risk factors is an effective tool for cancer prevention. Such estimates were recently calculated for the United States [1] and the United Kingdom [2]. This study is the first to estimate PAFs for cancer in Israel.

Material and method: In this study we estimate the PAFs for overall cancer and for several cancer types in adults aged 30 years and older in 2015 with respect to preventable risk factors, including active cigarette smoking, secondhand smoke (SHS) exposure, excess body weight, consumption of red and processed meat, low consumption of fruits and vegetables, dietary calcium, dietary fiber, consumption of alcohol, postmenopausal hormone use, and oral contraception.
Data on new invasive cancer cases in 2015 were retrieved from the Israel National Cancer Registry (INCR); 2015 is currently the last year for which data in the INCR are completed. Exposure data on nutritional factors were retrieved from a series of national studies on the status of health and nutrition in different age groups in Israel (MABAT) for 2014-2015. Exposure data on other factors were retrieved from the Israel National Health Interview Survey 3 (INHIS-3) which was carried out in 2013 through 2015 on a representative sample of the Israeli population.
Relative risks (RRs) for specific cancer types were retrieved from the scientific literature.
Israel PAFs were estimated using the following approximate formula:

where P_i is the exposure prevalence at the exposure category , and is the corresponding RR.

Results and discussion: (preliminary results, referring mostly to tobacco smoking and obesity and to the most prevalent cancer types) The fraction of lung cancer attributed to cigarette smoking in the Israeli population is 85% (all sexes), and that of colorectal cancer, 12% (all sexes). The attributable fraction of female breast cancer attributed to excess body weight in the Israeli population is 8%.

Conclusion: Identifying the contribution of modifiable risk factors to the incidence of certain cancer types in Israel offer an opportunity for primary prevention of cancer and enable informed decision-making with respect to the prioritization of interventions aimed to modify the exposure to these factors.

[1] Islami, F., Goding Sauer, A., Miller, K. D., Siegel, R. L., Fedewa, S. A., Jacobs, E. J., ... & Flanders, W. D. (2018). Proportion and number of cancer cases and deaths attributable to potentially modifiable risk factors in the United States. CA: a cancer journal for clinicians, 68(1), 31-54.

[2] Brown, K. F., Rumgay, H., Dunlop, C., Ryan, M., Quartly, F., Cox, A., ... & Huws, D. (2018). The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. British journal of cancer, 118(8), 1130.