IBS30.03 Risk Assessment to Establish Screening Programs: The Canadian Point of View

Abstract

The Canadian Task Force on Preventive Health Care (CTFPHC) supports screening with low dose computed tomography (LDCT) of the chest to decrease lung cancer mortality.1 The Task Force recommends annual screening up to three consecutive years in high risk adults aged 55-74 years with at least a 30 pack-year smoking history, who currently smoke or quit less than 15 years ago. Pilot LDCT screening program or studies are being conducted in Canada to help determine how to best implement organized lung cancer screening for people at high risk at the population level. Based on emerging data that suggests both the CTFPHC and the US Preventive Services Task Force (USPSTF) age and pack-years selection criteria2 are suboptimal and that risk prediction tools such as the PLCOm2012 are more sensitive with better positive predictive power to identify ever smokers who will develop lung cancer with a lower number needed to screen to prevent one lung cancer death and are more cost-effective,3-8 pilot studies in Canada adopt the PLCOm2012 risk prediction tool to select high risk ever smokers for LDCT screening. A prospective study is being conducted in newly diagnosed lung cancer patients in the Greater Vancouver area. In 1,076 patients, 37% were never smokers reflecting the foreign-born ethnic distribution. Of the 683 ever smokers, 60% met the PLCOm2012 model 6-year risk ≥1.5% screening criteria while only 39.5% met the USPSTF screening criteria. The International Lung Screen Trial (ILST), a multi-center prospective trial in Canada (British Columbia, Alberta), Australia, Hong Kong, and the United Kingdom, offer screening to ever smokers age 55 to 80 years if they meet the USPSTF criteria or the PLCOm2012 model 6-year risk ≥1.5% criteria. Participants receive two annual screens and are followed for six years for lung cancer outcomes. Interim results in 4,863 participants with 101 lung cancers showed that PLCOm2012 identified 26.6% more lung cancers than USPSTF criteria (99% of all lung cancers versus 78% with USPSTF). However, PLCOm2012 screened 9.9% more people than USPSTF criteria. If 2% six-year lung cancer risk threshold were used for screening selection criteria as is currently used in the Cancer Care Ontario Pilot, PLCOm2012 would be 12.7% more sensitive identifying 88.1% of lung cancers while screening 11% fewer people compared to USPSTF criteria. A 1.7% six-year lung cancer risk threshold would be 24.1% more sensitive identifying 97% of all lung cancers while screening only 1% more people than USPSTF criteria. The 1.7% threshold may be a better screening selection criterion. The worldwide burden of lung cancer is significant and projected to rise during the coming years especially in East Asian countries, namely, China, Japan, South Korea and Taiwan because of the large population size, high stable incidence rates in male and significant upward trends in females many of whom are never smokers.9 With global migration and increasing number of new Canadians who are diagnosed with lung cancer are from Asian countries such as in Vancouver, better lung cancer risk assessment tools need to be developed that take into account ethnicity and other environmental exposures such as outdoor and household air pollution exposures.10 Risk prediction tools may be perceived by some to be more complex to use than age and pack-years. The web based PanCan risk prediction tool, a precursor to the validated PLCOm2012 model, was tested in both English and French in 8 centers across Canada from coast to coast.7 The tool was found to be simple to use and took approximately 5 minutes to administer over the telephone. Similar experience was found with the web based PLCOm2012 risk assessment tool for enrollment into the International Lung Screen Trial and the Cancer Care Ontario pilot screening program. Risk assessment can be readily done by a navigator or a physician for enrollment into lung cancer screening programs as part of the shared decision process. Supported by the Terry Fox Research Institute, BC Cancer Foundation, the VGH-UBC Hospital Foundation, the Alberta Cancer Foundation, and the Australian NHMRC.