50 Years Ago: Q&A with Alumnus Peter Greenwald

October 2, 2023—Peter Greenwald ’73, MD, DrPH, distinguished former director of the National Cancer Institute’s Division of Cancer Prevention and Control, answers questions about his time as a graduate student and offers advice to current students.

Students today need to be aware of the world we live in and, hopefully, aim to make our world a better place. 

Take us back to the spring of 1973… What are your recollections from your time in our department? What was the environment like? How would you describe the academic atmosphere?

My ties to the Harvard T.H. Chan School of Public Health started as an MPH’67 student which combined rigorous epidemiological training with a network of student and faculty friendships. The next year as a teaching fellow, I started to develop ideas for my thesis. The fellowship was extremely valuable as it reinforced my epidemiological training, particularly as I mentored small groups of MPH students. Often 8-12 faculty and students had lunch together, discussing a wide range of national and international issues. This was particularly enjoyable.

As an Epidemic Intelligence Service (EIS) officer at the Communicable Disease Center, 1962-64, I learned “Shoe Leather Epidemiology” from Alexander Langmuir, a public health leader who created the EIS and advocated taking public health action immediately after field studies uncovered causes of outbreaks or other health problems. Brian MacMahon, was then the highly respected rigorous cancer epidemiologist heading the Harvard Chan School department. When applying to the MPH program, I naively asked MacMahon if I needed to take the first-year epidemiology course as I had been an EIS officer. He said something like, “You not only have to take it, you need to be deprogramed and learn the real epidemiology! EIS is a good program, but the problem is people come out of it thinking they know epidemiology.” In my career, I found that knowing both approaches was extremely valuable.

In 1968, Harriet and I married and moved to Albany where I became Director of Epidemiology at the New York State Department of Health. I planned to work on my thesis from there. Then I got into many other studies – the Love Canal toxic dump site, Hodgkins Disease, morbidity and mortality among recipients of blood from pre-leukemia and pre-lymphomatous donors and vaginal cancer after maternal treatment with synthetic estrogens (DES). The latter was published four months after Herbst et al’s landmark paper. While they demonstrated etiology, their publication seemed to be an end point. I took action: I drafted a letter for the state health commissioner to send to the New York Times and to the 25,000 New York physicians warning them of the danger of prescribing DES to pregnant women, and I advocated for and testified to House and Senate hearings, which forced the skeptical FDA to take federal action against prescribing DES.

What was the thesis writing process like for you? How did you pick the topic for your thesis “Epidemiologic Studies of Prostate Cancer?” Were there any particular challenges? Any unexpected surprises? What advice would you give to students just starting the thesis writing process?

Brian MacMahon and colleagues had demonstrated that adolescent factors – e.g., ages at menarche and first childbirth, height, and obesity — influenced breast cancer risk many years later. MacMahon also stimulated my interest in cancer epidemiology studies of causality. Thus, I wondered whether adolescent factors might influence prostate cancer risk. Harvard anthropologist Albert Damon helped me access detailed physical and anthropometric measurements on roughly 18,000 Harvard undergraduates who anthropologists had photographed, and then calculated and coded anthropometric indices thought to indicate maleness or femaleness (e.g., gynandromorphy, androgyny scales, body hair distribution, 25^th anniversary baldness, and other data re family. I was unable to find adolescent factors that influenced prostate cancer risk. In a different study, patients with prostatic hyperplasia were not at increased risk for prostate cancer.

I continued a focus on prostate cancer and later when directing the Division of Cancer Prevention and Control at NCI, decided epidemiology alone often was insufficient for prevention and turned my attention to randomized, double blind cancer prevention clinical trials. I was NCI sponsor and a participant in the 18,880-man Prostate Cancer Prevention Trial. This demonstrated that the drug finasteride reduced the risk of prostate cancer by about one third.

How would you link the work you did in your thesis to what you would go on to do in your later years as an epidemiologist?

Deep understanding of research methods by epidemiologists and the focus of my Harvard Chan School doctoral work greatly influenced my entering a 36-year career at the National Cancer Institute. The years at Harvard Chan helped me become expert in clinical trial and other research designs that go well beyond epidemiology. For example, in addition to director of NCI’s Division of Cancer Prevention and Control, for about seven years in the 1980s, I was editor in chief of the Journal of the National Cancer Institute. Papers were submitted from scientists in an enormous array of disciplines and sub-disciplines, from basic science, through epidemiology and clinical trials, to therapies and public health applications. Harvard Chan research training made me comfortable reviewing most types of papers, even though I generally asked experts in each particular field to be primary reviewers. I believe this type of knowledge can help every Harvard Chan School student.

 What advice would you give to current students in the department? Is there something you wished you’d known during your time as a student?

Students today need to be aware of the world we live in and, hopefully, aim to make our world a better place. To me, epidemiology often aims to know something while public health aims to do something. Think about both. Work on your thesis requires mentors expert in your particular area, but broaden your scope to get advice from those in other disciplines, perhaps even through relaxed, informal discussions. Thinking back, I feel in my studies closer contact with basic scientists and clinicians might have been helpful. I also liked considering Harvard Chan School’s potential impact on society.

Obviously, aim for work that merits publication. In academia, publications are key to tenure and promotion. However, some scientists seem to believe that if they retire with a very long bibliography, their life was a success. It may be more satisfying to act on your research findings to achieve public health benefits.

Curious to hear your thoughts about recent developments in epidemiology. What are some recent developments that you are most excited about?

Epidemiology benefits from the rapid advances in basic and clinical sciences, and the many areas where it can have an impact – individually, locally, and internationally. Artificial Intelligence (AI) and machine learning may provide wonderful opportunities for discerning unexpected relationships and ideas. Young epidemiologists have many opportunities to take advantage of these new approaches. Of course, they need to pay attention to validation, transparency and perhaps guarding against false AI output.

-Coppelia Liebenthal

Photo credit: Bill Branson, NIH