Abstract IA14: Lung cancer risk, image-based markers and screening
Authors: Schwartz Ann G. 
Published: March 2017

Ann G. Schwartz, PhD, MPH

Lung cancer is the most common cause of cancer death in the United States with an estimated 158,080 deaths in 2016 (accounting for 27% of all cancer deaths), and the second most frequent cancer diagnosed, behind breast cancer in women and prostate cancer in men, with an estimated 224,390 new diagnoses in 2016. Incidence and mortality vary by race/ethnicity, with higher incidence rates seen in African Americans (67.0 per 100,000) as compared to whites (60.2 per 100,000), even though African Americans tend to smoke fewer cigarettes per day than whites. African Americans also have a median age at diagnosis 4-5 years younger than whites. Survival is poor, with a 5-year survival rate of about 19.7% and disparities in survival by race/ethnicity remain. Five-year survival is higher among whites (20.0%) than among African Americans (16.6%). The 5-year survival rate has changed little over time reflecting the late stage at diagnosis. Fifty-seven percent of lung cancer cases in 2005-2011 were diagnosed at distant stages with only a 4.2% 5-year survival. For the 16% of cases diagnosed with localized disease, 5-year survival is 54.8%.

To dramatically improve survival, earlier diagnosis and improved treatments are needed. In the past few years, screening for lung cancer using low-dose computed tomography has proven effective in reducing mortality. In 2013, the US Preventive Services Task Force issued a recommendation for lung cancer screening for high-risk individuals. High-risk individuals eligible for screening are defined as being age 55-80 years old, having smoked ≥ 30 pack-years and having quit ≤ 15 years ago. These criteria will limit access to some groups, such as women and African Americans, who tend to have lower pack-year histories. The National Comprehensive Cancer Network (NCCN) recommends an extension of eligibility to those with a pack-year history of ≥ 20 and one additional risk factor such as chronic obstructive pulmonary disease (COPD) or an occupational exposure. It has been suggested that using a risk-based model for determining eligibility for screening would improve its effectiveness and efficiency. This strategy would increase the number of individuals eligible for screening, primarily by increasing the numbers of African Americans, current smokers, those with emphysema and those with a family history of lung cancer.

Retrospective evaluation of eligibility in a series of lung cancer cases can provide some insight into groups that might be missed as screening is being conducted today. We evaluated screening eligibility in 1052 lung cancer cases diagnosed in metropolitan Detroit. Fifty eight percent of this population was white, 39% African American and 3% other races. Eight percent of cases were never smokers. Only 41% of all cases would have been eligible for screening under NLST guidelines. The percentage of cases fitting NLST eligibility varies by race, with 44% of whites, 37% of African Americans and 30% of other races fitting into NLST categories. Only 38% of female cases fit screening guideline criteria. These data suggest that women and minorities will be under-represented in screening programs. In addition, 38% of cases had ≥ 30 pack-year histories but had quit years ≥ 15 years or fell outside the age range for screening. This is likely to be a high risk group that might benefit from screening. We are also evaluating image-based biomarkers to help identify high risk groups. COPD is considered an additional risk factor for eligibility under NCCN screening recommendations. We evaluated alternative measures of COPD based on spirometry and quantitative image analysis to better define a phenotype that predicts lung cancer risk. The odds of lung cancer were increased among those with COPD compared to those without as measured independently by percent voxels &lt; -856 HU on expiratory scan as a continuous measure of air trapping (OR=1.04; 95% CI (1.03, 1.06)) and FEV1/FVC &lt; 0.70 (OR=1.71; 95% CI (1.21, 2.41)). Measures of air trapping using quantitative imaging, in addition to FEV1/FVC, can identify individuals at high risk of lung cancer and might be considered as supplemental measures at the time of screening for lung cancer. These findings reflect a need to further refine screening guidelines, however, until a reduction in mortality can be associated with screening individuals outside the current guidelines it will be difficult to fully appreciate what greater impact might be gained from lung cancer screening.

Citation Format: Ann G. Schwartz. Lung cancer risk, image-based markers and screening. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr IA14.