Smoking and leukaemia

Chronic leukaemias

In recent years many subtypes of CLL and some CML variants have been recognized throughout the world by means of careful clinical, epidemiological, immunological, molecular biological and viral studies. Most striking has been the establishment of a close association between certain immunophenotypical subtypes of CLL and infection with HTLV-I and possibly HTLV-II. CLL has consistently been shown to have a strong genetic component and a low incidence among Asians, but a growing body of evidence also links this major leukaemia type with environmental factors including solvents, unidentified farming and other occupational exposures. In contrast, CML is characterized by few genetic associations, relatively homogenous world-wide distribution, greater frequency in Blacks than in Whites, little evidence of viral aetiology, and evidence that exposures to ionizing radiation, benzene and possibly other chemical agents are important aetiological factors. Most studies suggest that acquired rather than genetic factors are of greater importance in the aetiology of CML, but this conclusion is somewhat difficult to reconcile with the relatively small variation in incidence rates internationally. Common to both disorders in most populations are an increasing incidence with age, male predominance, and stability of incidence, survival and mortality over the years, exclusive of improved survival of CML following allogeneic bone marrow transplantation.

Smoking and risk of non-Hodgkin's lymphoma and multiple myeloma

Population-based case-control interview studies of 622 White men with non-Hodgkin's lymphoma and 820 controls from Iowa and Minnesota (United States) and 173 White men with multiple myeloma and 452 controls from Iowa offered the opportunity to investigate the relationship of these cancers with smoking. Risks were significantly elevated for all lymphoma (odds ratio [OR] = 1.4), high-grade lymphoma (OR = 2.3), and unclassified lymphoma (OR = 2.8) for cigarette smokers. Dose-response gradients were not seen with intensity of cigarette use, but risks for these subtypes were greatest for cigarette smokers of longest duration. Similar elevations in risks were seen for tobacco users. The risk of multiple myeloma was not significantly elevated for either tobacco users or cigarette smokers. The findings from this study confirm the lack of an association between smoking and multiple myeloma and provide some support for an association between tobacco use and certain subtypes of non-Hodgkin's lymphoma.

Mortality among petrochemical science and engineering employees

This is a study of a dynamic cohort of 13 250 commercial research and development personnel for whom information on occupational and educational background and smoking was available. Their age-, sex-, race-, and period-adjusted death rates were compared with New Jersey rates and with an internal comparison population. The overall results were favorable. The study groups had significantly fewer deaths from most major disease categories compared with other New Jersey residents. Among white male scientists and engineers, age-adjusted overall mortality and ischemic heart disease mortality were comparable to white male managers and support staff studied, whereas mortality from leukemia and lymphatic cancer was significantly elevated. Mechanics, however, had a significantly lower leukemia and lymphatic cancer mortality rate than did the comparison group. In a Poisson regression model in which white males and females from the study population were used, and for which the effects of age, smoking, college education category, period of hire, and years employed were controlled, scientists, engineers, and research technicians had elevated (nonsignificantly) mortality rates for leukemia and lymphatic cancer compared with managers and support staff. Smoking was an independent risk factor for leukemia and lymphatic cancer. Further work is needed to assess if specific environmental factors, such as benzene, other aromatics, radiation, medical treatment, and smoking habits, might have contributed to the above findings.

Association between smoking and leukemia in two American Cancer Society prospective studies

The association between smoking and leukemia in men and women was analyzed from the data of two prospective studies. Myeloid leukemia was positively associated with smoking in men in both studies (standardized mortality ratios [SMR], 2.44 and 1.32; P less than 0.05), but not with smoking in women. Lymphatic leukemia showed no elevation in risk in men and women in both studies. Animal studies suggest a real biologic difference in leukemogenic effect between the sexes, but further analyses are needed to characterize the smoking effect of leukemia in women.