Genetic screening for CLL premature, speaker says
Photo courtesy of the
National Institute
of General Medical Science
NEW YORK—Research has shown that family history is a strong risk factor for developing chronic lymphocytic leukemia (CLL).
First-degree relatives have an 8.5-fold risk of getting CLL and an increased risk of other lymphoproliferative disorders, according to a study published in 2009.
However, despite the strong evidence of a genetic contribution, one expert believes it’s premature to bring genetic testing into the clinic for screening in CLL.
“At this time, we do not recommend genetic screening,” said Susan Slager, PhD, of the Mayo Clinic in Rochester, Minnesota.
“There’s no known relationship between the inherited variants and treatment response,” she explained, and the relatively low incidence of CLL argues against active screening in affected families at present.
Dr Slager discussed genetic and non-genetic factors associated with CLL and the clinical implications of these factors at Lymphoma & Myeloma 2016.
Demographic risk factors
Dr Slager noted that age, gender, and race are risk factors for CLL.
Individuals aged 65 to 74 have the highest incidence of CLL, at 28%, while the risk is almost non-existent for those under age 20, she said.
There is a higher incidence of CLL in males than in females, and the reason for this gender disparity is unknown.
There is a higher incidence of CLL in Caucasians than Asians, for both males and females.
“Again, it’s unknown why there’s this variability in incidence in CLL,” Dr Slager said. “Obviously, age, sex, and race—these are things you can’t modify. You’re stuck with them.”
However, several studies have been undertaken to look at some of the potentially modifiable factors associated with CLL.
Beyond demographic factors
The International Lymphoma Epidemiology Consortium, known as InterLymph, was initiated in 2001 to evaluate the association of risk factors in CLL. Study centers are located primarily in North America and Europe, with one in Australia.
In one of the larger InterLymph studies, investigators evaluated risk factors—lifestyle exposure, reproductive history, medical history, occupational exposures, farming exposure, and family history—in 2440 CLL patients and 15,186 controls.
The investigators found that sun exposure and atopy—allergies, asthma, eczema, and hay fever—have a protective effect in CLL, while serological hepatitis C virus (HCV) infections, farming exposure, and family history carry an increased risk of CLL.
This confirmed an earlier study conducted in New South Wales, Australia, that had uncovered an inverse association between sun exposure and non-Hodgkin lymphoma (NHL) risk, which fell significantly with increasing recreational sun exposure.
Medical history
Another earlier study from New South Wales revealed a 20% reduction in the risk of NHL for any specific allergy.
However, the investigators of the large, more recent study observed little to no evidence of reduced risk for asthma and eczema.
The underlying biology for atopy or allergies is a hyper-immune system, Dr Slager explained.
“So if you have a hyper-immune system, then we hypothesize that you have protection against CLL,” she said.
Another medical exposure investigators analyzed that impacts CLL risk is HCV. People infected with HCV have an increased risk of CLL, perhaps due to chronic antigen stimulation or possibly disruption of the T-cell function.
Height is also associated with CLL. CLL risk increases with greater height. The concept is that taller individuals have increased exposure to growth hormones that possibly result in cell proliferation.
Another hypothesis supporting the height association is that people of shorter stature experience more infections, which could result in a stronger immune system. And a stronger immune system perhaps protects against NHL.
