| dc.description.abstract | Lung cancer is the second most common cancer and the leading cause of death from cancer in the US. Carotenoids, with the property of anti-oxidation and immunoregulation, have been demonstrated to have an anti-carcinogenesis effect. However, results from the previous studies investigating the associations of dietary carotenoids and vitamin A intakes and their circulating biomarkers with lung cancer risk have been inconclusive. Interventional trials among high-risk individuals showed that supplements of β-carotene increased the risk of lung cancer. Observational studies found inverse or nonsignificant associations of dietary carotenoids and vitamin A with lung cancer risk. The prospective studies showed inverse associations of circulating α-carotene, β-carotene, and total carotenoids with lung cancer risk; however, the associations of different isomers and subtypes of common carotenoids, including carotene, cryptoxanthin, lycopene, lutein, zeaxanthin, and retinol with lung cancer risk have not been well investigated. In addition, the studied populations in the previous studies were mainly conducted on European descendants or Asians, but barely among African Americans (AA) and low-income population, regardless of the exposures were measured by food frequency questionnaires or blood samples. AAs, especially AA males, experienced the highest incidence of lung cancer of any racial or ethnic group in the United States. People living in a lower socioeconomic status (SES) were likely to experience a disproportionate burden of lung cancer compared with those in the higher SES.
We prospectively examined associations of lung cancer risk with carotenoids and vitamin A and related circulating biomarkers with different isomers and subtypes in the Southern Community Cohort Study (SCCS). SCCS is a pre-dominantly low-income AA and European American (EA) population cohort and includes about 86,000 participants, two-thirds of whom are AAs. In the Aim1, we analyzed 65,550 participants including 1,204 incident lung cancer cases and estimated the associations using multi-variates cox proportional hazards regression models. We observed dietary intakes of carotenoids and vitamin A were not associated with overall lung cancer risk. Increased vitamin A intake was found associated with an increased risk of lung cancer among current smokers and adenocarcinoma among African Americans. In the Aim2, we conducted a nest case-control study including 225 incident lung cancer cases and 429 controls individually matched on age, race, and sex. Plasma trans-β-carotene, cis-β-carotene, total β-carotene, and trans-anhydrolutein were inversely associated with lung cancer risk. The associations remained significant after excluding cases diagnosed within the first year of follow-up. The inverse associations of plasma cis-β-carotene, total β-carotene, and trans-anhydrolutein with lung cancer risk were more evident among AAs, males, and former and never smokers. For the stratification analysis, further studies with a larger sample size are warranted to confirm our findings. | |
