Impact of Obesity and Genetic Variation in Energy Balance and Metabolism Genes On Prognosis in Diffuse Large B-Cell Lymphoma (DLBCL) and Follicular Lymphoma (FL)

Obesity has been associated with an increased risk of developing of lymphoma, particularly DLBCL. Genetic variation in several energy balance genes, including leptin (LEP), its receptor LEPR, ghrelin (GHRL) and neuropeptide Y (NPY) have been shown to modulate risk of lymphoma, although their impact on survival is not known. In contrast, recent studies suggest that patients either overweight (Body Mass Index (BMI), 25 to<30 kg/m²) or obese (≥30 kg/m²) may have a superior prognosis in DLBCL, although its impact in FL and in the current treatment era is not known. We evaluated the association of BMI at the time of diagnosis, 2 years prior to diagnosis and at ages 18, 35 and 50 years, along with germline genetic variation in selected energy balance genes with event-free (EFS) and overall (OS) survival in DLBCL and FL.

We evaluated these associations in a prospective cohort of newly diagnosed DLBCL (N=764) and FL (N=649) patients enrolled at the Mayo Clinic and University of Iowa from 2002–2009 as part of the Molecular Epidemiology Resource. Peripheral blood DNA, clinical data and self-reported historical weights were collected at enrollment. Patients received standard disease treatment strategies, and were systematically followed for disease progression, re-treatment, and death. Single nucleotide polymorphisms (SNPs) were genotyped as part of a custom Illumina iSelect panel. The most prevalent homozygous genotype was used as the reference group, and each SNP was modeled as having a log-additive effect in the regression model. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) for the association of the obesity measures and SNPs with outcome, adjusted for treatment class and subtype specific prognostic factors (IPI, FLIPI).

For DLBCL patients (median age 63 years, range 18–92) the median follow-up was 47 months (range 0–101); 58% had an IPI 0–1 risk disease; and 87% received immunochemotherapy. For FL patients (median age 60 years, range 25–94), the median follow-up was 60 months (range 11–110); 24% had FLIPI score 3–5; and main initial treatments were observation (32%), rituximab (R)-monotherapy (12%), CVP +/−R (19%), and anthracycline +/−R (22%). The main results for BMI and prognosis are reported in the Table. For DLBCL, obese patients at diagnosis had better EFS and OS; this association was weaker for BMI at age 50 and 35 years. In contrast, for FL, overweight and obese patients at diagnosis had a poorer EFS and OS, and this was also observed for BMIs two years before diagnosis and at ages 50 and 35 years. In FL, the LEP SNP rs2167270 was associated with inferior EFS (HR=1.25; 95%CI 1.05–1.49) and OS (HR=1.28; 95%CI 0.90–1.83). The NPYSNP rs16147 was associated with inferior FL OS (HR=1.50; 95%CI 1.03–2.17) but was not associated with EFS. None of the energy balance and metabolism SNPs were associated with DLBCL EFS or OS.

Higher BMI prior to and at diagnosis, as well as SNPs in LEP and NPY,were significantly associated with FL prognosis, with inferior outcomes in overweight and obese patients. These novel findings in the modern treatment era suggest an important role of obesity pathways in FL prognosis. In DLBCL, we confirm the recent findings of improved survival in DLBCL in obese patients, and extend this to the modern treatment era and BMI earlier in life.

No relevant conflicts of interest to declare.