Cancers of the Lung and Pancreas in Acadiana
In 1975 and 1976,the National Cancer Institute first published maps of the United States showing regional death rates for specific types of cancer in each of the 50 states for the time period 1950-1969. Separate volumes were prepared for mortality in Whites and "Nonwhites." In Louisiana, the nonwhite population for the 20-year period 1950-69 was overwhelmingly Black/African American. Therefore, these ethnic/racial groups will be referred to broadly as White and Black. These so-called "cancer maps" highlighted parts of the U.S. where the death rates for specific cancers were unusually high or low and served to stimulate grant funding to test hypotheses about factors that might be related to elevated death rates in certain places.
The cancer maps graphically displayed high death rates for cancer of the lung in south Louisiana primarily among men, both Whites and Blacks. High death rates for cancer of the pancreas in White and Black men and White women in parts of south Louisiana were also noted. The maps themselves have been updated over time, and examples are shown below for cancer of the pancreas in White men and women for 1970-80.
The most recent maps can be found on the website for the National Cancer Institute at http://www.nci.nih.gov.
Following publication of the first set of maps, the National Cancer Institute issued a call for research to study risk factors for these cancers that might explain the high rates in particular geographic areas. Louisiana State University School of Medicine was funded to conduct three case-control studies, including one on cancer of the lung and a study of cancer of the pancreas in the early 1980s. The two studies yielded important information about these cancers and have stimulated additional research by Louisiana scientists and scientists elsewhere. The findings of these studies will be briefly discussed and subsequent and on-going research will follow.
Consistent with the findings of others, the relative importance of cigarette smoking in the risk of lung cancer in Louisiana cannot be overemphasized. The lung cancer study included interviews with 1253 lung cancer cases and 1274 matched controls. Approximately 98% of all male lung cancer cases were current or former smokers, as were 94% and 88% of the Black and White female cases, respectively. A 12 to 25-fold increased risk of lung cancer was observed among smokers in Louisiana compared to non-smokers, depending on the number of years smoked and the amount. Non-filter smokers had double the risk of smokers of filter cigarettes. Persons who started to smoke before the age of 16 had three times the lung cancer risk of those who began smoking after age 20. This study was the first U.S. study to find an increased risk of lung cancer in non-smokers exposed to the smoke of others (also called passive smoke, environmental tobacco smoke, or ETS). Many other studies throughout the world have subsequently confirmed a small but significant increased risk in ETS-exposed non-smokers. A follow-up study of lung cancer in non-smokers conducted by these LSU researchers in the mid-1980's to early 1990's found a two-fold increase of lung cancer in non-smokers with a family history of lung cancer.
Diet was examined as a risk factor for lung cancer in Louisiana. Low intake of fruits and vegetables was found to increase lung cancer risk, as did low dietary intake of vitamin C and all types of carotenes combined. This study was one of the earliest studies to report this "protective effect" of fruits and vegetables, and this finding has been consistently confirmed all over the world. The specific components of fruits and vegetables responsible for this reduced risk have not been clearly determined. Fruits and vegetables contain vitamins such as vitamin C and folate, beta-carotene and other carotenoids, minerals, fiber and phytochemicals or non-nutrient substances contained in food. Whether it is one or more of these components or the full "package" that decreases the risk of lung cancer and other epithelial cancers, the message is clear that five or more daily servings of fruits and vegetables is important to a healthy lifestyle.
Occupation was examined in this study, and Louisiana men employed in forestry occupations, particularly sawmill workers, were found to be at increased risk of lung cancer. Consistent with this finding was an increased risk in persons who reported occupational exposure to wood dust. Subsequent studies in other geographic areas have also found an increased risk of lung cancer associated with wood dust exposure. A two-fold increased risk of lung cancer was also found for occupational exposure to mineral oil mist.
The pancreatic cancer study also conducted in the early 1980's included 363 persons with pancreatic cancer and 363 matched controls -- persons of similar age, sex, and race without pancreatic cancer. In this study, several findings suggested a role of inherited susceptibility. A two-fold increased risk of pancreatic cancer was found among persons reporting Acadian ancestry. An almost two-fold increased risk of pancreatic cancer was observed in persons reporting a family history of any cancer, increasing to a five-fold increased risk in persons with a family history of pancreatic cancer. It should be noted, however, that families often share not only genes but also a common environment and lifestyle, so this familial risk may represent either an inherited susceptibility or similar exposures or both.
Cigarette smoking is a risk factor for pancreatic cancer, one of the few well-documented risk factors. However, the smoking-associated risk of pancreatic cancer is much smaller than that for cancer of the lung. A two-fold increased risk of cancer of the pancreas was found in this study for cigarette smokers.
The relationship of diet to pancreatic cancer risk in Louisiana was examined in detail. Significant increases in pancreatic cancer risk were found among persons who consumed large amounts of pork and processed meats and large amounts of rice, breads and cereals. The level of risk tended to increase with increasing amounts of pork products and dairy products consumed by men; among women, risks increased with increasing consumption of seafood. This is called a "dose-response." In others words, the higher the "dose" the greater the "response" or, in this case, risk. As in the lung cancer study, frequent consumption of fruits was "protective"; that is, persons with low intake had about double the risk of those with higher consumption. Neither alcohol nor coffee was associated with risk.
Employment in professional and managerial occupations and sugarcane farmers had significantly increased risks, between one and a half and two-fold. And a doubling of risk was seen in persons who lived in rural areas compared to urban areas. The risks associated with both rural residence and with each of the dietary factors were more apparent in persons reporting Acadian ancestry, suggesting a possible gene-environment interaction.
Since these studies were completed, the epidemiologists at LSU School of Medicine have continued to study these and other cancers common in the Louisiana population. The earlier studies were entirely based on responses to questions asked by interviewers in structured questionnaires. More recently, scientific and technological advances have allowed researchers to address the issue of susceptibility to specific exposures. Individuals with equal exposure to the same carcinogen differ in their biologic response. Inherited mutations in genes, such as the "breast cancer genes" BRCA1 and BRCA2, are relatively rare and account for only about 15% of all breast cancers. Other individual differences in common genetic traits responsible for how a person handles (activates or detoxifies) carcinogens now appear to be important determinants of risk. Wide differences in these traits have been documented between individuals, and differences in the distribution of these traits have also been found among different racial/ethnic groups. The latter may account for some of the differences in cancer risk observed in different racial and ethnic groups, in addition to differences in lifestyle and other exposures.
Two epidemiological studies by researchers at L.S.U. are currently in progress, one of lung cancer in southeast Louisiana funded by the Environmental Protection Agency and one of pancreatic cancer in the Lafayette/Acadiana region funded by the Louisiana Board of Regents. Each study seeks to address risks associated with environmental and lifestyle exposures as well as risks associated with differences in genetic traits responsible for the activation or detoxification of substances believed to be important in risks of these two cancers.
For cancer of the lung, our primary interest is in several genes responsible for metabolizing "polycyclic aromatic hydrocarbons" (PAH). These compounds are found in cigarettes are also produced in certain industrial settings, and are believed to be important contributors to risk. We will examine whether any of these genetic traits responsible for handling PAH increases risk of lung cancer and whether certain exposures only increase risk in persons with traits that make them unusually susceptible.
Some chemicals in a group of compounds called N-nitrosamines are carcinogenic and have been shown to cause pancreatic cancer in laboratory animals. Their role in human pancreatic cancer is unclear at this time. Nitrosamines and other related compounds have been found in pork products and cigarette smoke, each of which has been shown to increase risk of pancreatic cancer in our earlier Louisiana study. Further, vitamin C, found in fruits and associated with a lower risk of pancreatic cancer, can inhibit the formation of N-nitrosamines. In our recently initiated study of pancreatic cancer in Acadiana, we will focus on genetic differences in several genes responsible for activating and detoxifying N-nitrosamines. We will also study the role of other potential carcinogens that may be related to our earlier study.
to Learn More:
Fontham ETH, Haenszel W, Pickle LW, et al. Dietary vitamins A and C and lung cancer risk in Louisiana. Cancer 62:2267-2273, 1988.
Falk RT, Pickle LW, Fontham ETH, et al. Lifestyle and pancreatic cancer in Louisiana: a case-control study. Am J Epidemiol 128:324-336, 1988.
Fontham ETH, Correa P, Reynolds, P et al. Environmental tobacco smoke and lung cancer in nonsmoking women: a multicenter study. JAMA 271 (22): 1752-1759, 1994.
Wu AH, Fontham ETH, Reynolds, et al. Family history of lung cancer and risk of lung cancer among lifetime nonsmoking women in the United States. Am J Epidemiol 143 (6):535-542, 1996.
Heath C and Fontham ETH. Cancer Etiology. In, The American Cancer Society's Clinical Oncology. Lenhard RE et al Editors. Blackwell Science Inc., Maiden MA, pp. 37-54, 2000.