John L. Marshall, MD: Hello. I'm John Marshall, director of the Ruesch Center for the Cure of Gastrointestinal (GI) Cancers at Georgetown Lombardi Comprehensive Cancer Center in Washington, DC. I want to welcome you to the 2016 Ruesch Center Annual Symposium, "Fighting a Smarter War Against Cancer," where we bring experts together to do just that. My fundamental principle is to invite people I want to hear from to our symposium. I am joined today by Marcia Cruz-Correa, who is a professor of medicine and biochemistry at the University of Puerto Rico's Comprehensive Cancer Center in San Juan.
CRC Second Most Common Cause of Cancer Death Among Latinos
Thank you for joining us, to discuss some of the key issues that Latino populations face in regard to colorectal cancer that may distinguish them from other populations. How are you addressing them?
Marcia R. Cruz-Correa, MD, PhD: If you look at the US Latino population, it is really very diverse. Depending on where you are, the group of Latinos that you see is different. If you are on the West Coast of the United States, you see people who are usually from Mexico. If you go to the East Coast, you see Latinos who usually come from the Caribbean and Central America. The word "Latinos" actually represents a very diverse group of people who have their genes coming from very different places. You have Latinos who have more African ancestry; you have Latinos who have more Indian ancestry or more European ancestry. Because of that, the risks in those populations also vary.
"When you ask a Latino anywhere in the United States, 'Do you have a risk of getting colon cancer?' The most common answer is 'no.'" When you ask a Latino anywhere in the United States, "Do you have a risk of getting colon cancer?" the most common answer is "no." Women think their risk is for breast cancer. Men think their risk is for prostate cancer. But guess what? Colorectal cancer is the second most common cause of cancer death among Latinos, and that should not be the case.
Dr Marshall: Are there any particular stigmas? No one wants to be screened for colon cancer. Are there any particular stigmas within the Latino population around this?
Dr Cruz-Correa: I think the biggest barrier is not knowing about it. Once you know that you are at high risk of getting colorectal cancer, like any other group in the United States, then there is an issue of stigma. One of the things that we talk about is the machismo within different groups. When you look at the data, colorectal cancer incidence is higher among men than women, especially in the Latino population. It's not a huge difference, but the numbers are there. It tells you what is happening. Are women getting screened more than men? The answer is yes. That could be one of the barriers—the machismo of having a colonoscopy. What I tell them is to forget about the one day of doing a colonoscopy, that it could actually save their lives.
Dr Marshall: All of us need to drill down on all populations to get screenings done.
Dr Cruz-Correa: Absolutely.
Does the Reason for Increased Incidence Lie in Latino Genes?
Dr Marshall: Can we figure out on a genetic level why some people are getting colon cancer and some people are not? We have talked about the obvious explosion, or at least emergence, of a great number of young people with colorectal cancer. Can you talk a little bit about your own personal research and what you are doing in that space?
Dr Cruz-Correa: For me, this is personal. Whenever I see a patient in their 30s or early 40s—someone who is working and has kids, and then they present all of a sudden with rectal bleeding or weight loss—and I do a colonoscopy and find cancer, it really hits me. Those are the individuals that we are not looking at because the US screening guidelines say to start screening at age 50,[1] except for African Americans; the American College of Gastroenterology recommends that we start earlier for them, at age 45.[2] But the data are not out and people are not doing that. Why is that? When you look at the incidence of colon cancer in Latinos in their countries, it is lower. When they move to the United States, the incidence goes up. People have been looking for the reasons. My laboratory has been focused on the genes. We've been trying to see whether the genes that we inherit really increase our risk of getting cancer. Or, rather than the genes, is it something that we are doing? We have found certain hits that are more prevalent among people from Latin communities or Latin countries.
Dr Marshall: Where are your populations? Tell me a little about where you are getting the samples from.
Dr Cruz-Correa: I am in Puerto Rico right now. We have a large cohort of people from the island as well as from the Caribbean. We have people from the Dominican Republic, Jamaica, and some other nearby islands. To look at genes that increase your risk for colon cancer, you need many, many people. So we joined a big team in the United States to be able to look at about 6000 individuals. From that group, we have about 4000 controls and another 2000 or so who have cancer. About 25% of those samples are Latinos from Puerto Rico and the Caribbean. That is important. People group all Latinos together and all Asians together, but their genetics vary.
The question is, can genes explain it all? I don't think so. I think that the genes increase risk, but that happens only in a very few number of people who get hereditary cancer—maybe 5% of everyone who gets colon cancer. What happens to the others? I think genes can be modified by the way we eat. That is the second big question that we have in our laboratory. We are looking at bacterial genes in the gut and whether we can modify the expression of the genes that are produced by the bacteria with what we eat.
Dr Marshall: That is what we are looking for, too—some sense of control. Can we actually understand? We are what we are. We are our genes, but can we influence our risk by what we eat? We read so much about that and there are conflicting data. It would be nice to have some real science that drives us in that direction. How far away are we from something like that? I feel like it's just the beginning.
Dr Cruz-Correa: I agree with you. There is so much information that we don't know. I always put this in the perspective of those classic people who have hereditary cancer. So, let's look at the Lynch syndrome population. Those individuals are born with a mutation in the gene, one of the mismatch repair genes that increase the risk of getting colon cancer. You would say that if the mother has the mutation in one of her genes, she passes it to her children. You would expect that all of them, the mother and the children, will have the same risk of getting colon cancer, but the answer is no. You could have a very high penetrance mutation, a high risk of getting colon cancer, yet your risk of getting cancer is different. How do you explain that? Because we are not one gene. If we were one gene and you look at what we eat and our environment, everybody would have the same thing. It doesn't happen because the expression of proteins of the genes is modified by other genes.
It could also be that food, the environment, and everything else that we are exposed to changes expression of other factors that actually develop cancer. So, in that model, if we don't even see it, how can we see it in people who have a mixture of genes? I think that it is much more complex. We are trying to understand that.
Dr Marshall: I am very excited and can't wait to hear the rest of the story that you are going to tell us later today at our symposium. Dr Marcia Cruz-Correa, thank you so much for coming up to Washington, DC, to share your insights at the symposium.
Dr Cruz-Correa: Thank you for having me here.
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Cite this: High Rate of Colorectal Cancer in Latinos--Are Genes, Stigma, or Other Factors to Blame? - Medscape - Mar 20, 2017.
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