Pelayo Correa was born in Sonson, Colombia on 3 July 1927. He received his MD in 1949 from the Universidad de Antioquia in Medellin and served on the faculty of the Universidad del Valle School of Medicine in Cali from 1954 until 1970. He was a Visiting Scientist at the US National Cancer Institute from 1970 to 1973, and then joined the faculty of Louisiana State University Medical Center, New Orleans, where he was Professor of Pathology from 1974 through 2005. In 1996 he was designated as a Boyd Professor, the highest academic rank in the LSU System. After retirement from LSU he joined the faculty of Vanderbilt University Medical Center where he continues to do research. Dr. Correa is the founder of the Cancer Registry in Cali, Colombia, the first population-based registry in Latin America, and was a leader in the development of the SEER Louisiana Tumor Registry in New Orleans. He is the author of over 500 publications and is the Principal Investigator of an NCI Program Project on the etiology of gastric cancer, which has been continuously funded since 1980. He has received numerous awards and honors for his seminal contributions to the natural history of gastric carcinogenesis.
EF: What was the path that brought you to epidemiology?
PC: When I went to medical school I was not really interested in curing patients one by one. I was curious about diseases, their etiology and pathology. I have always had that interest beyond the individual case. As a result I became a pathologist. After medical school I had a straight pathology internship. There is a state in Colombia called Antioquia, and at that time there was only one pathology laboratory serving the whole state. That laboratory was responsible for every histologic diagnosis of cancer. I became interested in looking at the numbers and the statistics. When we graduated as medical doctors, we had to write a thesis based on an original piece of work, so I decided to do a study of cancer statistics in Antioquia. I focused on the relative frequencies of specific types of cancers. I confirmed many findings that we believed to be the case but that had not previously been documented.
I left for additional training in pathology at Emory University. While there, I attended a meeting in Washington D.C. on geographic pathology and presented my paper on cancer statistics in Antioquia. My presentation was published, and this encouraged my interest.
When I returned to Colombia I worked at Universidad del Valle in Cali. Our laboratory was responsible for all the pathology diagnoses for the city. I began to look at the cancer statistics for the city of Cali. In May 1961, I attended a meeting of the Latin American Society of Pathology where I presented the data. The organizers had invited Dr. Harold Stewart, who was Chief of Pathology at the National Cancer Institute (NCI) in Bethesda. He was interested in my work and took my handouts to Bethesda, where he showed them to Bill Haenszel, who was Chief of Biometry at the NCI. Bill then came to Cali and we decided to start a cancer registry in Cali.
I learned so many things from Bill. When I began looking at cancer statistics I didn't know that I had to limit the cases to a specific geographic area, or that I could only count actual residents of that area, or that I could only count new cases, and so forth. He just took me by the hand and we created the population-based cancer registry which is still operating today. It is the longest-running cancer registry in Latin America, going for over 45 years. It has been a wonderful experience, and many studies have been carried out based on that registry.
Bill also helped me find a way to finance it. We didn't have any money so he went after 2 sources. The first was a grant of $3000 for “high risk projects” from the Fuller Foundation, a part of the Fuller Brush Company. Then Bill found a US law that allowed any surplus from US agricultural grants to other countries to be used for scientific purposes in that country. Bill applied for surplus funds in Colombia, and we got a grant that kept us going—so I suppose I entered epidemiology through the side door.
EF: What would you say is the biggest difference between epidemiology as it was practiced when you first started out and today?
PC: I was introduced to epidemiology in Colombia, where there are huge differences in cancer rates. Cancer has always been my focus—the differences in rates in different populations. It is very efficient to work with the community there because the population is cooperative and very stable. The problems were that there was no money and that Colombia did not have a well-developed research culture. I don't know what the situation was in the United States at that time. What I knew was through Bill Haenszel and his research was very focused. Today the discipline has grown greatly, but the application of epidemiology has become more diffuse. It seems less focused on solving specific problems in etiology.
EF: What person has most strongly influenced your career?
PC: I would have to start with my pathology professor, Professor Alfredo Correa-Henao. He was the Chief of Pathology at our medical school. He was a modest and humble man, but very strict scientifically. He emphasized the need to be intellectually honest. Sometimes in pathology it is not very popular to express a point of view that is not shared by the clinicians. He taught me to be intensive and to dig deeply in seeking the correct answer.
But the most influential person in my professional life was Bill Haenszel. I consider him to be my intellectual father. I was so fortunate to have him in my life. He came often to Cali. He helped me in every aspect of my budding career in epidemiology, as I mentioned, securing funding but also helping with technical matters related to the registry and encouraging me to take advantage of opportunities—especially analyzing cancer registry data. He guided me from point A to point Z.
EF: What have you found to be the most important ingredients in a good collaboration?
PC: I consider myself an “etiologist” because my interests lie in trying to find out what causes cancer. I work as a part of a team, and the other members of this team include clinicians, laboratory scientists, and of course statisticians to back us up and keep us honest. I think collaboration is essential, an integral part of our work.
EF: Who would you regard as the 2 or 3 most important epidemiologists during your lifetime?
PC: The most important epidemiologist in my lifetime was Sir Richard Doll.1 No question about that. His work goes far beyond the UK—he set an example for the world. One of his major contributions was establishing the link between tobacco and cancer. In the beginning many people didn't believe this finding, but his studies were so thorough and so objective that his work eventually convinced the world that this was the truth. He has influenced epidemiologists all over the world.
In my personal experience Bill Haenzel has to be mentioned again. He was objective, honest, dedicated and insightful. He was responsible for many things, such as the migrant studies, for example. This was the first methodologic approach to try to separate genetic influences from environmental influences, and his studies on stomach cancer in the Japanese are classic. His work established that children of Japanese migrants, even though of Japanese ancestry, did not have the high rates of stomach cancer seen in their parents or in Japan. Genetics was not the primary determinant for this cancer. This was the beginning of the study of what is now called gene-environment interactions.
Of course, there were 2 other stars within epidemiology in this country, Abraham Lillienfeld and Brian MacMahon,2 who were leaders in epidemiology education. Another person who has very much influenced this field is Joe Fraumeni from the National Cancer Institute. He is so respected within the NIH in general and, as a result, has influenced the policies of the NIH. He leads a very strong intramural program that has competed well with the extramural programs and, thus, has been a very important influence in cancer epidemiology.
EF: In turning from other epidemiologists back to you, I wonder if you could share what you think your most influential paper was, and which has been least appreciated.
PC: Well, I'd have to say that the most influential paper is the Lancet 1975 paper, in which we described the cascade of premalignant lesions leading to stomach cancer.3 In those days, epidemiologists looked at cancer cases (and controls) as though the cancer appeared magically overnight. Many epidemiologists have told me our paper caused them to think about what events happened before the actual diagnosis of cancer. Of course, our passive smoking research has also been important. I think this research was critical to the EPA and others as it helped establish the association in a large, sound study. As was the case with Sir Richard Doll and active smoking, at first few believed that a person smoking close to you was harmful, but this association is now clear.
I would have to say the most underappreciated and frustrating work was not a paper but a program. When I was in Cali, Colombia, cervical cancer was the most important cancer. The incidence rate was very high so we started a cytology program. We convinced relevant government agencies and some private enterprises to set up a central laboratory because I knew that quality control was crucial. The American Cancer Society gave us a little money to buy a microscope and some instruments for cervical cytology. We started a screening program in Cali and within only a few years the rate of invasive cancer declined and the rate of in situ cancer of the cervix increased. This shift to earlier stages was parallel with the development of the cytology screening program, providing good support of its effectiveness. After that apparent success, the bureaucrats got involved. They split up the central laboratory, and the extent and effectiveness of cytology screening declined. In Latin America in general we have not done an adequate job in preventing cervix cancer. Developments of science and technology do not guarantee access and success. Societal forces can impede progress.
EF: How have you chosen the research questions that you want to address?
PC: It's all about curiosity. I am very interested in the burden of disease in populations, and I have always been interested in trying to understand “why.” For example when I was in Colombia many years ago I started to study endemic goiter, which was very common then. We wrote papers and described the disease and as a result the government began to put iodine in the salt and endemic goiter just disappeared. I am attracted to problems that are really relevant. I ask “why” and then I take it from there. Right now I am working in stomach cancer and Helicobacter pylori. As part of our program project we have found that there are big differences in the rate of stomach cancer and precancerous lesions in the southern part of Colombia. The people who live in the Andes mountain region have a very high prevalence of infection of H. pylori and very high rates of stomach cancer. However, the people who live along the coast have a very high prevalence of infection but do not have a high rate of stomach cancer. That's my present challenge—why is this happening?
EF: And I wish you every success in finding out. What have been your major interests outside of epidemiology?
PC: I am a workaholic so I don't have a lot of interests outside my work, except of course my family. They are what I enjoy the most. I'm very fortunate to have a wonderful wife and kids, and grandchildren who are a joy. I spend a lot of time with them and I enjoy every minute of it. Unfortunately, Hurricane Katrina brought some disruption to our family because some of the family had to be split. I am also interested in the burden of problems in populations, and I link that to politicians and administrators and the people who are the leaders of society. I am interested in studying the history and etiology of these problems, reading books about the players involved and contemporary world leaders. I am interested in trying to figure out what things are important, and to understand the narrow-minded approach of leaders who make decisions whose consequences are suffered by the society.
EF: What has been epidemiology's most important contribution to society?
PC: Our field's contributions have been great, but not very well appreciated. I think that most understanding of causation has been reached through an epidemiology pathway. Sometimes the people who study the links between cause and effect don't call themselves epidemiologists, but that's what they are. They are studying the phenomena that are happening in their society. Although, PhD epidemiologists and doctors of public health in epidemiology are few in number, they have had great influence. You have molecular biologists, chemists, pharmacologists, and occupational scientists doing epidemiology, although it may not be so clear to others in the scientific community.
EF: What is your assessment of the current state of the health of epidemiology?
PC: I worry a little bit about the health of epidemiology because it's become less focused, more diffuse. You have excellent departments of epidemiology in many universities but I see 2 trends. Some centers are emphasizing such a technical epidemiology that it almost becomes philosophical and mathematical. Some become fascinated with the philosophy and mathematics, and forget that epidemiology is a utilitarian science to benefit society. There's another trend that's curious to me. Social epidemiology focuses almost exclusively on disparities in health in the communities. Sometimes the focus is on the political implications; very interesting to a scientist, but it is not so clear what impact this has on society. That's somewhat out of the reach of epidemiologists, but researchers spend many hours and dedicate entire meetings to that kind of exercise.
EF: What do you see as our richest opportunities?
PC: Epidemiology has become intimately related to molecular biology recently. Molecular biology has been very fruitful. For instance, some years ago all the drugs to treat cancer were cell poisons. Now we can look at the molecular mechanisms and develop interventions based on the molecular pathways. That's going very well, but there's a danger there that the epidemiology may become so molecular that the big picture of cause-and-effect is lost. Another opportunity that I think is under-used is international studies. There are many examples of unique situations in countries outside the United States or Western Europe that one could target for study. Unfortunately it is hard to be funded for that.
EF: Do you have any predictions about what the future might hold?
PC: I hope that epidemiology will continue to influence all the other basic and clinical scientists. But as I see these 2 dichotomies, the mathematical/philosophical and the social/political branches, going off separately, I cannot know or guess what's going to happen in 30 or 40 or 50 years.
EF: What then would be the single most important piece of advice you could give to a new epidemiologist just starting his or her career?
PC: The advice I would give is to stick to your instincts and your guesses and the things that interest you most. Success in any discipline comes from working on what truly interests you. Even if you are wrong with your first hypothesis, don't abandon the area. Continue with solid studies with a strong basis. I would say not to depend on senior epidemiologists excessively too soon because then you lose your spark, you lose your thrust. You can consult them later, though, for advice and consideration of future directions.
ABOUT THE INTERVIEWER
ELIZABETH T. H. (TERRY) FONTHAM is Dean of Louisiana State University School of Public Health. She has worked for many years with Pelayo Correa. She is a cancer epidemiologist focusing on tobacco- and diet-related cancers. She helped to establish the risk of lung cancer associated with secondhand smoke exposure and has published extensively with Correa on premalignant lesions leading to gastric cancer. She has been a contributing author for the Surgeon General's Reports and IARC Carcinogenesis Monograph series, and serves as national President of the American Cancer Society.
1. Darby S. A conversation with Sir Richard Doll. Epidemiology
2. Willett W. A conversation with Brian MacMahon. Epidemiology
3. Correa P, Haenszel W, Cuello C, Tannenbaum S, Archer M. A model for gastric cancer epidemiology. Lancet
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