We previously found that African Americans and Native Hawaiians were at highest lung cancer risk compared with Japanese Americans and Latinos; whites were midway in risk. These differences were more evident at relatively low levels of smoking intensity, fewer than 20 cigarettes per day (CPD), than at higher intensity. Methods: We apportioned lung cancer risk into three parts: age-specific background risk (among never smokers), an excess relative risk term for cumulative smoking, and modifiers of the smoking effect: race and years-quit smoking. We also explored the effect of replacing self-reports of CPD with a urinary biomarker - total nicotine equivalents - using data from a urinary biomarker substudy. Results: Total lung cancers increased from 1979 to 4993 compared to earlier analysis. Estimated excess relative risks for lung cancer due to smoking for 50 years at 10 CPD (25 pack-years) ranged from 21.9 (95% CI = 18.0 to 25.8) for Native Hawaiians to 8.0 (95% CI = 6.6 to 9.4) for Latinos over the five groups. The risk from smoking was higher for squamous cell carcinomas and small cell cancers than for adenocarcinomas. Racial differences consistent with earlier patterns were seen for overall cancer and for cancer subtypes. Adjusting for predicted total nicotine equivalents, Japanese Americans no longer exhibit a lower risk, and African Americans are no longer at higher risk, compared to whites. Striking risk differences between Native Hawaiians and Latinos persist. Conclusions: Racial differences in lung cancer risk persist in the Multiethnic Cohort study that are not easily explained by variations in self-reported or urinary biomarker-measured smoking intensities.
Bibliographical noteFunding Information:
This work was supported by the National Cancer Institute (U01 CA164973, Understanding Ethnic Differences in Cancer: The Multiethnic Cohort Study and P01CA138338, Mechanisms of Ethnic/Racial Differences in Lung Cancer Due to Cigarette Smoking).
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