Invited Commentary: Menthol Cigarettes and Risk of Lung Cancer

Abstract

The association between lung cancer and cigarette smoking was first established with the publication of several important papers in the middle of the last century (2–4). A decade and a half later, the 1964 US Surgeon General’s report on Smoking and Health (5) provided a clear and definitive judgment on the challenge of smoking, which continues to play an important role in public health, individuals’ pain and suffering, and domestic and foreign politics (6–9). Despite the overwhelming evidence linking tobacco smoke, particularly from cigarettes, and lung cancer, anomalies are evident when comparing aggregate, population-level exposures with tobacco and lung cancer rates of populations. These anomalies can be seen in international comparison studies (10) and in comparisons of subgroups at varying risk within countries, as Brooks et al. (1) note. Prominent among these are the high lung cancer rates for US Blacks. According to statistics from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute (11), lung cancer incidence rates for Black men are 50 percent higher than for White men, while the combined data of the National Program of Cancer Registries (NPCR) and SEER (12) indicate a 26 percent higher incidence in Black men. Differences in the incidence rates of lung cancer are interesting in that over the period of etiologic relevance for these incident cancers (i.e., about 20–25 years previously), the prevalence of smoking (about 20 percent higher in Blacks) and the average number of cigarettes consumed per smoker (about 30–40 percent higher among Whites) combine such that overall exposure to the primary risk factor of interest actually appears to have been lower in Black men than in White men (13–15). In the most recent data, lung cancer incidence rates for Black women are similar to those for White women, that is, about 3 percent higher in the 1996–2000 SEER data (11) and 7.5 percent lower in the 1999 NPCR-SEER data (12). Smoking prevalence rates from the previous 20–25 years indicate a slightly higher rate of smoking overall (33 percent vs. 29 percent) (13–15). Despite this apparent consistency between smoking and lung cancer rates, a disparity exists; Black women smoke many fewer cigarettes: 60 percent (vs. 30 percent of Whites) smoke fewer than 15 cigarettes a day, and only 6 percent (vs. 22 percent of Whites) smoke 25 or more cigarettes a day (14). Underscoring their public health significance, lung cancer mortality rates track well against incidence in women and men of both races, with women’s death rates lagging slightly (11) mainly because their smoking rates rose after those for men (13–15). Because lung cancer tends to be a fatal disease, unexplained elevations in incidence place a large burden on a population subgroup already beset by a host of other health problems. Cancers of the upper aerodigestive tract also have been shown to be related to exposure to tobacco (16, 17), and unexplained racial disparities in these rates disfavor Blacks to an even greater extent (11, 12). This fact has added further impetus to the search for the cause(s). This search has led in a number of directions, such as exploring intrinsic differences in levels of enzymes that metabolize products of tobacco combustion (18–21) and, more recently, investigating various genetic polymorphisms that could influence the carcinogenicity of tobacco (22–26); evaluating other lifestyle factors that might influence the carcinogenic potential of tobacco (27–29); and examining differences in the types