Upper Lobe Tumors and Asbestos Exposure

Over 2,000 new cases of Mesothelioma are diagnosed each year in the United States (making up about 3 % of all cancer diagnoses).  The more research that is dedicated to finding a cure for this disease, the better.  One interesting study is called, "A Meta-Analysis of Colorectal Cancer and Asbestos Exposure" by David M. Horna, David H. Garabrant, and Brenda W. Gillespie -  American Journal of Epidemiology Vol. 139, No. 12: 1210-1222.  Here is an excerpt: "A meta-analysis of the relation between asbestos exposure and colorectal cancer mortality was conducted, using published reports of 20 asbestos-exposed cohorts. Summary standardized mortality ratios (SMRs) for colorectal cancer were examined in relation to asbestos type and estimates of dust exposure (as direct estimators of asbestos exposure) and in relation to lung cancer SMR and the proportion of all deaths due to mesothelioma (as proxy estimators of asbestos exposure). An elevated summary SMR was observed in cohorts exposed to amphibole asbestos (summary SMR = 1.47; 95% confidence interval (Cl) 1.09–2.00), but not in cohorts exposed to serpentine asbestos (summary SMR = 1.04; 95% Cl 0.81–1.33) or in cohorts exposed to both serpentine and amphibole asbestos (summary SMR = 1.03; 95% Cl 0.74–1.42). Cohorts having a lung cancer SMR greater than 2.00 had a summary SMR of 1.51 (95% Cl 1.29–1.76), and cohorts in which more than 1 % of all deaths were attributed to mesothelioma had a summary SMR of 1.24 (95% Cl 0.94–1.64), After stratifying the cohorts based on mortality due to all cancers excluding those known or suspected to be associated with asbestos exposure, lung cancer mortality was not clearly associated with colorectal cancer mortality, suggesting that the crude association between these factors may be due to misdiagnosis of lung cancer as other types of cancer in the reported causes of death. These results suggest that exposure to amphibole asbestos may be associated with colorectal cancer, but these findings may reflect an artifact of miscertification of cause of death. The results also suggest that serpentine asbestos is not associated with colorectal cancer."

A second study is called, "Association of Cigarette Smoking and Asbestos Exposure with Location and Histology of Lung Cancer" by BURTON W. LEE, JOHN C. WAIN, KARL T. KELSEY, JOHN K. WIENCKE, and DAVID C. CHRISTIANI - Am. J. Respir. Crit. Care Med., Volume 157, Number 3, March 1998, 748-755.  Here is an excerpt: "Prior studies have suggested that lung cancers that arise in association with cigarette smoking favor an upper-lobe location while those associated with asbestos exposure favor a lower-lobe location. An excess of adenocarcinomas has also been reported among cases not exposed to cigarette smoke as well as among those exposed to asbestos. However, these studies typically have not adjusted adequately for potential confounders such as the patient's age, sex, race, or family history of cancer. To better examine the effects of cigarette smoking and asbestos exposure on location and histology of lung cancer, we analyzed data from a large case-control study that included 456 patients with stage I or II lung cancer. Patients with upper-lobe tumors tended to have had more exposure to tobacco as assessed by pack-years smoked (54.7 versus 46.2, p = 0.07) and less time since quitting smoking (3.0 versus 5.5 yr, p = 0.05). In contrast to some prior reports, asbestos exposure was also associated with an upper-lobe location of tumor. Among those with upper-lobe tumors, 14.6% had a history of significant asbestos exposure compared with 5.4% of those with lower-lobe tumors (p < 0.01). The relationship between asbestos exposure and upper-lobe location of tumor was also statistically significant whether stratified by smoking or analyzed by multivariable logistic regression modeling. Adenocarcinomas were more likely among those with less exposure to cigarette smoke based on fewer pack-years smoked (41.5 versus 61.8, p = 0.0001) and more time since quitting smoking (5.0 versus 3.0 yr, p = 0.02). The proportion of patients with significant exposure to asbestos was lower among those with adenocarcinomas but was not statistically significant (9.5 versus 15.3%, p = 0.09). In multivariable logistic regression analysis, longer time since smoking exposure remained a significant predictor of adenocarcinomas (p < 0.02), but history of asbestos exposure did not predict tumor histology. Thus, in patients with lung cancer, both cigarette smoking and asbestos exposure histories favor an upper-lobe location of tumor. Longer time since smoking exposure favors adenocarcinomas, but the history of asbestos exposure does not appear to influence the tumor histology."

If you found any of these studies interesting, please read them in their entirety.  We all owe a great deal of thanks to the people who are researching these important issues.