Abstract PR03: Association of environmental risk factors, family history, and polygenic risk scores with chronic lymphocytic leukemia
Authors: Kleinstern Geffen , Robinson Dennis , Call Tim G. , Liebow Mark , Sanjosé Silvia de , Benavente Yolanda , Cerhan James R. , Slager Susan L. 
Published: May 2019

Background: Chronic lymphocytic leukemia (CLL) is a lymphoid malignancy with a strong genetic component. There are over 30 common single nucleotide polymorphisms (SNPs) associated with the risk of CLL. Moreover, in the InterLymph Subtypes Project a number of non-genetic exposures have been found to be associated with CLL, including family history (FH), height, history of atopic conditions, UV radiation, and farming exposures. However there has not been a study evaluating the joint effects among these genetic and non-genetic factors with CLL risk.

Methods: Using the Mayo Clinic CLL case-control study of 587 newly diagnosed CLL cases and 790 controls, we performed analyses evaluating joint effects of genetic and non-genetic factors. For genetic effects, we computed a polygenetic risk score (PRS), a weighted averaged of the number of risk alleles across 34 SNPs, with the weights being the log of the odds ratio for each SNP. Exposure data was available for 65% of the cases and 79% of the controls. We evaluated individual and joint associations of FH of any hematological malignancy, total sun exposure categorized by quartiles based on the controls, ever living or working on a farm, any atopy, any allergies, asthma, height, and PRSs categorized by quintiles based on the controls. Multivariate logistic regression analyses were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

Results: In our preliminary results, the frequency of CLL cases in the upper PRS quintile was 49% while in the lowest quintile only 5%. The PRS has a strong evidence of association with CLL (OR= 3.04, CI =2.20-4.20 for highest versus the middle quintile). When adjusting for PRS, we still found a positive association with FH for any hematological malignancy (OR = 1.90, CI = 1.25-2.88), FH of non-Hodgkin lymphoma (OR = 2.02, CI = 1.08-3.79), and FH of leukemia (OR = 1.73, CI = 0.98-3.07). When stratifying by FH, the upper quintile of the PRS had a 5.85-fold (CI = 1.69-20.3) increased risk of CLL relative to those in the middle quintile in the FH strata, and a 2.65-fold (CI = 1.75-4.01) increased risk in the non-FH strata.

After adjusting for PRS, FH and age, there remained an inverse association with sun exposure in the highest quartile (hours per week) (OR = 0.49, CI = 0.31-0.79) and a positive association with height (per 10 cm change) (OR = 1.37, CI = 1.17-1.62), but there were no associations with atopy, any allergies, history of asthma, or farming. No statistical evidence of an interaction among the variables was observed.

Conclusions: We found evidence of independent effects among the genetic and non-genetic factors with risk of CLL. Among these factors, the PRS had the largest effect size. Although we did not observe any statistical interactions, larger sample sizes are warranted to fully evaluate these effects on risk of CLL. We are currently increasing our sample size through collaboration with other research groups. Final results will be presented in the meeting.

This abstract is also being presented as Poster A06.

Citation Format: Geffen Kleinstern, Dennis Robinson, Tim G. Call, Mark Liebow, Silvia de Sanjosé, Yolanda Benavente, James R. Cerhan, Susan L. Slager. Association of environmental risk factors, family history, and polygenic risk scores with chronic lymphocytic leukemia. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr PR03.