CLL: Role of Lifestyle, Environmental Exposure

There can be no doubt about the fact that your genetics influences your chance of getting CLL.  CLL is a familial cancer, with too many family clusters of patients to ignore. If you are a CLL patient, chances that your kids or grandkids will also be diagnosed with CLL at some point in their lives goes up seven-fold, compared to the general population.

There is also no doubt that different genetic pools of people have different risk of getting CLL.  This disease is a lot more common in the Western countries than it is in the East.  But that may be changing.  A just  published article in “Blood” underlines this distinction between the importance of genetics and the role played by lifestyles and / or environmental factors in risk of CLL. The abstract is below; send me a personal email if you want help locating the full text article.

Blood. 2010 Aug 16. [Epub ahead of print]

The incidence of chronic lymphocytic leukemia in Taiwan, 1986-2005: a distinct, increasing trend with birth-cohort effect.

Wu SJ, Huang SY, Lin CT, Lin YJ, Chang CJ, Tien HF.

Division of Hematology, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan;

Abstract

The incidence of chronic lymphocytic leukemia (CLL) in Taiwan is markedly lower than that in Western countries, but we have seen a drastically increasing trend. We explored this distinct incidence trend of CLL for Taiwanese. The epidemiologic data of CLL for Taiwanese and Caucasian Americans during 1986-2005 were obtained from the Taiwan National Cancer Registry and Surveillance, Epidemiology, and End Results Program, respectively. The individual effects of time period and birth cohort on the incidence trends were analyzed using an age-period-cohort model. Though there was a weak period effect corresponding to the increased applications of immunophenotyping in 1991-1995 in Taiwan, evidences suggested that the age-adjusted incidence rate of CLL for Taiwanese was continuously increasing during the 20-year period while that for Caucasian Americans remained steady. In addition, a much stronger birth-cohort effect was identified for Taiwanese but not for Caucasian Americans. This effect corresponded to the westernization of lifestyle in Taiwan since 1960. We conclude that, in addition to the ethnic difference of incidence, there is distinct increasing incidence trend of CLL in Taiwan. The strong birth-cohort effect underlying this increasing trend indicates that lifestyles and environmental factors may play a role in the development of CLL for Taiwanese.

PMID: 20713960

CLL in Taiwan

As the authors point out, CLL occurrence in Taiwan is significantly lower than that in America (Caucasian Americans – important to get that distinction, we are truly a melting pot of various ethnic groups). CLL is the most common adult leukemia in the West, with an incidence rate of between 2-6 cases each year per 100,000 people. In Taiwan, the rate is more than ten-fold lower, typically about 0.3 cases each year per 100,000 people. The graph below summarizes the information.

Changing trends over time

While Taiwanese people continue to be less at risk of CLL incidence even to this day, there is clear evidence that things are changing over time. In Caucasian Americans the incidence remained remarkably steady for both sexes, (between 3.9 – 4.1 for men and 1.9 - 2.1 for women) over this time period. But that is not the case in Taiwan. There the incidence of CLL increased both for men and women, 0.16 to 0.47 for men and 0.05 to 0.24 for women. Give them another couple of decades and it is easy to see CLL will be just as prevalent in that part of the world too. What fun, misery loves company.

This is the kind of stuff that epidemiologists love to track and analyze. The data shows something is changing in Taiwan, causing more people to develop CLL. Since it is not likely that the genetic make-up of Taiwanese people has changed during this time period, the authors express strong suspicion that the causes are likely to be environmental factors or lifestyle changes.

The age of industrialization began around 1960 in Taiwan. Once industrialization takes root, can Big Macs be far behind? Younger Taiwanese consume more calories, their diets are more likely to have higher percentage of animal fat and protein than the traditional Taiwanese diet practiced by their parents. This is also reflected in increasing incidence of childhood obesity in kids, something that was not very common at all prior to Westernization of their dietary habits. Industrialization is also invariably accompanied by higher degree of exposure to chemicals, pesticides, herbicides, radiation and other potential carcinogenic hazards. Increasing prosperity level also brings higher consumption of tobacco products, cosmetic products such as hair dyes etc.

It is interesting to note that there is a clear sex difference in the incidence of CLL, both in Caucasians and Taiwanese. More men get CLL than women. But the increasing trend of CLL in Taiwan is shown clearly for both men and women, suggesting that whatever changes in lifestyle or environmental factors that are driving this increase effects both sexes equally.

How about them viruses?

Di you know mice can get leukemia too? There is this particular virus called MLV (Murine leukemia viruses), one of the members of a family of retroviruses known to cause cancer in mice, that has been in the news recently. Recent studies have linked it to chronic fatigue syndrome.

We wrote about the role of viral infections in an earlier articles, and specifically the murine leukemia virus. Please refer to them for more details.

Let’s see:  CLL patients are immune compromised; therapy often makes the immune suppression worse than it was, at least for a period of time while their bodies recover from the insult of chemotherapy drugs. Our guys are likely to get all sorts of viral infections during periods of deep immune suppression. How about MLV, is this one of the risk factors? I have not seen any reports linking MLV to the mind numbing fatigue experienced by CLL patients, one of the infamous “B-symptoms” that suggests therapy is not too far away. By the way, this virus has also been linked to other cancers such as prostate cancer in humans. The article below suggests as many as 10 million people in the US are infected with murine leukemia virus and it is spread from human to human.

Retrovirus Linked to Chronic Fatigue Syndrome

XMRV Seen in 2/3 of CFS Patients; 10 Million in U.S. May Carry Virus

By Daniel J. DeNoon

Oct. 8, 2009 – Some 10 million Americans may carry a recently discovered retrovirus now linked to chronic fatigue syndrome.

The virus, xenotropic murine leukemia virus-related virus or XMRV, was detected in 67% of 101 patients with chronic fatigue syndrome by Vincent C. Lombardi, PhD, of the Whittemore Peterson Institute in Reno, Nev., and colleagues.

The researchers also found the virus in nearly 4% of healthy comparison subjects — suggesting that millions of Americans may carry the mysterious virus, which was first detected in prostate cancers.

“The discovery of XMRV in two major diseases, prostate cancer and now chronic fatigue syndrome, is very exciting. If cause and effect is established, there would be a new opportunity for prevention and treatment of these diseases,”said Robert H. Silverman, PhD, of Cleveland Clinic’s Lerner Research Institute, in a statement emailed to WebMD.

Where did the virus come from? The virus is closely related to a retrovirus that’s become part of the mouse genome. Oddly, XMRV cannot infect mouse cells — but can easily infect human cells. It’s unlikely that so many humans have caught XMRV from mice. It’s more likely that the virus is spread from human to human, but how that happens remains to be seen.

“If these figures are borne out in larger studies, it would mean that perhaps 10 million people in the United States and hundreds of millions worldwide are infected with a virus whose pathogenic potential for humans is still unknown,” they write. What is known is that viruses closely related to XMRV do cause many different diseases — including cancer — in other warm-blooded animals

I am being just a tad paranoid here, but someone said paranoid people have real enemies too. What is the take home message?  There is a lot of stuff out there that you cannot do much about. But you can and must take responsibility for the things you do control – such as your diet, your level of personal hygiene, exercise, avoidance of situations where you are more likely to catch nasty viral infections. CLL patients do not get much joy from vaccinations, so we must be extra vigilant in prevention of infection in the first place. 

The Taiwanese experience reported above suggests that genetics are not the only game in town, that lifestyle and environmental factors play a role as well in the incidence of CLL. If you are a CLL patient, you cannot go back in time and prevent it from happening in the first place - that train has already left the station. In your case, you already have the damn disease and all you can do is figure out how to deal with it as intelligently as you can.

But how about your kids and grandkids? Sure, they have this not-so-lovely genetic gift courtesy of your CLL. But that does not mean they are guaranteed to get diagnosed with CLL down the road. It just means the odds are higher than if they had no first degree blood relative with CLL. How about shifting those odds downward for them, with a few smart changes in lifestyle and general awareness of cancer prevention?Even if CLL is not in their future, they surely will be healthier and happier if they avoided some of the common health hazards prominently displayed on our grocery shelves. Get your kids to quit playing quite as many computer games or watching TV, get them to go out and play – like prior generations of kids used to do. Help them to avoid the dangers of smoking, teach them good habits of personal hygiene. You know, all the commonsense things we all know are good for us.