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Issue 21 Interview Transcript

Adam Weiss: Welcome to the JNCI podcast, a production of the National Cancer Institute. I’m Adam Weiss.

Adam Weiss: In a paper published online on October 26, researchers looked at cancer rates among Israeli Jews who may have lived through the holocaust. We want to hear from someone whose work could be directly affected by this study, so I have Dr. Gad Rennert on the phone with me from HIFA, Israel. He wasn’t involved in the study, but Dr. Rennert is the Chairman of the Department of Community Medicine in Epidemiology at the Carmel Medical Center and the Teknion University. He is also the Director of the National Cancer Control Center at CHC, the largest healthcare provider in Israel. Welcome Dr. Rennert.
Dr. Gadi Rennert: Good morning.
Adam Weiss: So I guess it’s been known for a while that cancer rates are higher among Israelis who came from Europe, and this study looked at whether that had anything to do with the terrible experience that some of them may have had during the holocaust, right?

Dr. Gadi Rennert: Yes, true.

Adam Weiss: Now, the authors looked at 300,000 people, but they were careful to say that these people were potentially exposed to the holocaust, and avoided saying holocaust survivors almost entirely. Why did they make that distinction?

Dr. Gadi Rennert: It’s very hard to actually know, especially from a database, whether a specific person has been exposed to any of the horrors of the holocaust because there were many different experiences. So the indicator was really if you immigrated in to Israel from Europe at any year after, you know, the year when World War II ended, you would be considered according to the article to be eligible for the study.

Adam Weiss: So this was a study of essentially records in a database. The others looked at people’s age and when they came to Israel, and made the assumption that these people were likely to have been affected in some way by what happened during the holocaust.

Dr. Gadi Rennert: They were potentially likely to be affected. It’s tricky to actually – this is one of the biggest issues with interpretation of the result, you know, what we’re seeing is actually really holocaust effects or other effects because the holocaust had a long spectrum of exposures. The people who were in Auschwitz were in a super catastrophic situation. Then there were people in concentration camps which were not death camps. Then there were people in work camps, okay. Then were people in ghettos, and then there were populations that were not affected at all like in Romania, about sixty percent of Romania was not affected at all. And again in Russia, by no means can you read the period as a happy period. They were in war, and the wars were awful, there were bombs ________________, et cetera, et cetera, but they were not in holocaust.

Adam Weiss: So these are people from varied life situations, but the study did show there’s something the group had in common was a significantly higher rate of cancer. I want to get your thoughts on the reasons for that in a minute, but first I want to know how this information is available to do the study. This is something that isn’t possible to do in some countries, but Israel actually has a National Cancer Registry and the bureau statistics, and you can take two things together to get this kind of information, right?

Dr. Gadi Rennert: Yes, being an immigrant country, we do have a lot of information about immigration history which is pretty readily available, and yes we do have a cancer registry that goes back all the way to the early 50’s. It’s one of the better cancer registries in the world, very comprehensive covering a long period, and actually, you know, matched only by maybe registries that we can find in Scandinavian countries. For the general question, and as much as you can get data out of, you know, a database study, this is really a very good resource.

Adam Weiss: And this paper used that resource to look at the relationship between living in Europe at that time and cancer. One of the things the author said they were looking at was caloric restriction, that’s not getting what we generally think is enough to eat. Now, I thought there would have been studies showing that restricting calories

had a positive effect on getting cancer, but these people got more cancer than normal.

Dr. Gadi Rennert: Yeah, well, we know that calories usually are promoters of the carcinogenic process. So actually caloric restriction was always considered to be an event that blocks cancer from developing rather than something that promotes development of cancers. I think there have been numerous studies, both in animals where you can actually control what you feed them, as well as in humans with former experiences which is actually one of the reasons to think that if this in fact is true, then it potentially is not because of the caloric restriction aspect of it.

Adam Weiss: In the paper, I saw that they talked about experiences people had in Norway, in Japan, where they didn’t get enough food to eat for some period of time, but these weren’t as severe in terms of the number of calories or the other experiences that the people were going through as the holocaust survivors may have experiences, right?

Dr. Gadi Rennert: This is true. I mean the degree of calorie restriction in people who were actually in the camps was extreme. I mean I don’t think that even experimental models could actually replicate this extreme situation. So, you can only learn to a limited extent from the other natural or planned studies.

Adam Weiss: Something that I saw in the paper which really struck me was that they caloric restriction as being referred to as under nutrition without mal-nutrition, but that wasn’t the case for these people. They were really mal-nourished, right?

Dr. Gadi Rennert: Very much so. Well again, one has to be extremely careful. Most of these people probably were not mal-nourished. Only a fraction of them was. I mean people who came for say the former USSR, you know, the Russian Republic, their involvement in the concentration camp aspect of the holocaust was relatively low. They had other hardships. By no means can I say that they had a lot of food or enough food, but the camps- the concentration camps experience is probably a phenomena that only a minority of all of these accounted for in the study have underwent. The only clear thing that we have from this paper is a comparison of people of the same age, same ethnic group of people who arrived in Israel prior to World War II compared to people who arrived after World War II. So the difference, is not a time difference, is not an ethnicity difference, age difference, it’s a location difference. And some thing in being in Europe around the years of war, and again some countries were terribly affected, some were mildly affected, something in being there at that time of World War II made a difference.

Adam Weiss: The authors of the paper speculated, at least, that a difference could be not just caloric restriction, but for people who were exposed to the conditions in concentration camps or other more severe situations during the holocaust that it was some of the stress that they experienced, physical, mental stress, other things that happened to them that could have increased that. What do you think of that point of view?

Dr. Gadi Rennert: Well, I think that there’s a very good chance that this kind of explanation is more plausible than the caloric restriction. I really think that to a large extent, it is possible that the stress component was responsible more than the caloric restriction.

Adam Weiss: So what does it take to find out? The holocaust happened seventy years ago. I mean could it just be that these people smoked and drank and lead riskier lives because of their traumatic experiences? Now that we have this study, what do we do to find out more about what causes the difference?

Dr. Gadi Rennert: Yeah, well, you know, we can speculate and speculate, it’s very hard to tell, especially of course not from a database based study. I mean there’s no individual information on exposures, not prior and not after being diagnosed. So this is really, I mean this study cannot answer that. Cancer overall is such an environmental, you know, disease, and it depends so much on your health habits that just comparing two groups without knowing anything about what is the difference in the risk factors. You know, that is as much as you can get from that type of let’s call it ecological approach. You can’t get more than that from it. And frankly, I’m more interested in the stress point than in the caloric restriction point just because if we want to learn from it for the future, then stress is something that many of us would probably be exposed to in the future, and it’s very important to know whether it’s a significant risk factor for cancer. This has not been shown significantly until now, while such an extreme degree of caloric restriction is not a very common phenomena. And hopefully, you know, events like the holocaust will just not recur. So, you know, I mean like if you want to bring it in to practice, you know, the findings and translate it in to something meaningful, then the stress issues are a potentially more relevant.

Adam Weiss: So what could be done after this study to expand upon what they found to draw out some more information? What other studies could build on this, and what would those studies do to give you the information that you’re really looking for?

Dr. Gadi Rennert: Well, look, this generation’s kind of disappearing on us now. Many of the people in this database have perished already, and the younger of them are probably in their seventies. So frankly, I mean the only possible approach right now to look in to that a little more in to depth is to go in to say case control studies where you would look at cases of say breast cancer or colorectal cancer, I’m mentioning these two because they were mentioned in the paper as the two leading sides with access incidents, and go for case control studies of colorectal and breast cancer, and try to evaluate the actual holocaust exposure of the people, or the actual nutritional exposure of the people in younger ages, et cetera. Compared to age, sex, whatever matched controls, and there you will have whether the rate was really increased or not, but you will able to control that increase for a lot of exposures. So I mean I think that is the only way to go on this issue. Of course, again, if you accept it to be not a holocaust-related phenomena but a simple extreme stress related phenomena, then you can run after a million other groups in the world that have been in stressful situation and see if you can replicate the results in one of these groups. With the holocaust, you know, it’s a time issue, like they’re fading away from us because the population is disappearing.

Adam Weiss: Well it sounds like this research will inspire people to look in other directions as well, and it could end up revealing some more surprises about cancer. Thanks so much for talking with me today.

Dr. Gadi Rennert: Okay, you’re welcome.

Adam Weiss: And thank you for listening to the JNCI podcast. For more interviews, audio summaries of JNCI issues, and more information about today’s topic, visit To get in touch with us, send an email to, or follow us on Twitter, we’re at JNCI_now. If you like this episode, please share it with your colleagues and friends. I’m Adam Weiss, thanks again for listening.