Identifying Demographic and Disease Related Differences in Hispanic Vs Non-Hispanic Patients with Classical Hodgkin Lymphoma

Introduction:

Classical Hodgkin Lymphoma (cHL) makes up the majority (90%) of Hodgkin lymphoma cases. It is further categorized into 4 subtypes - nodular sclerosis, mixed cellularity, lymphocyte rich, lymphocyte dependent. Incidence of cHL varies based on age, socioeconomic status, HIV status, EBV status, geography, race/ethnicity. (PMID 21197477) Studies have shown that survival rates vary between non-Hispanic (NH) and Hispanic (H) patients. (PMID 22241896) Our study aims to identify differences in disease characteristics, demographics and outcomes among NH and H population diagnosed with cHL.

Methods:

This is a retrospective study of a cohort of patients diagnosed with lymphoma from the Surveillance, Epidemiology and End Results (SEER) database. Patients with cHL diagnosed from 2000 to 2018 were identified by the International Classification of Diseases for Oncology Third Edition (ICD-O-3) code list. Standard demographic variables collected include sex, race, age at diagnosis, subtype of lymphoma, stage, B-symptoms, and radiation therapy among others. Categorical outcomes were summarized with frequencies and percentages and median age (years) was the only continuously distributed outcome with the median. The significance of variation in the distribution of categorical outcomes with ethnicity (HI, NH) was assessed with Fisher's Exact tests or Pearson's Chi-square tests as appropriate; median age was assessed with Wilcoxon tests. Survival time was measured in years from date of primary diagnosis to date of death. Patients not coded as dead were considered censored on survival time at the date last seen. Survival distributions were described with Kaplan-Meier curves and the significance of variation in median survival with ethnicity was assessed with log rank testing and proportional hazards models with propensity score weighting based on age. At risk tables were computed based on the Kaplan-Meier estimate of the survival curve. All statistical testing was two-sided with a significance level of 5%.

Results:

Overall survival in cHL, based on Kaplan Meier estimates, was not statistically significant (p 0.67) between the two groups. Survival probability for cHL at years 2,5, 10 years in NH was 0.864, 0.804, 0.733 and in H, it was 0.855, 0.804, and 0.737. There was no statistical difference (p0.082) between females (45.9% NH, 44.7% H) and males (54.1% NH, 55.3% H). The median age at diagnosis was higher in NH at 39 years (y) than H at 34y (p<0.001). NH patients were diagnosed the most (27.9%) between 2005-2019 vs H patients were diagnosed most (28.9%) between 2010-2014 (p<0.001). White patients made up the majority in both NH (79 %) and H groups (95.3%, p<0.001). There was no statistical difference in the site of disease with extranodal cHL being 2.5% in NH and 2.0% in H (p0.017); with nodal cHL, it was 97.5% in NH and 98.0% in H (p0.017). Stage II was the most common stage at diagnosis in NH (33.7%) and in H (29.8%, p<0.001). B symptoms were present less in NH (18.5%) vs in H (22.8%, p<0.001). The presence of B-symptoms was unknown in a higher number of NH (60.2%) vs H (55.0%, p<0.001). Lastly, radiotherapy was administered more in NH patients (30.7%) than H (26.7%, p<0.001). However, upon multivariate cox regression with adjusting for age, H patients have increased risk of death as compared to NH patients (p -value 0.0e+00, CI 5.92-6.72).

Conclusion:

Our study of cHL patients found several statistically significant differences within the NH and H groups. NH patients are older at the time of diagnosis, are less likely to have B-symptoms and are more likely to receive radiotherapy as compared to H patients. Most importantly, using multivariate cox regression with adjustment for age, H patients have an increased risk of death compared to NH patients. However, further research is needed to see what other differences exist between the two groups and help better explain the increased risk of death in H. Our study also adds to the growing list of data that highlights the difference in various demographic and treatment measures in NH and H patients.

Diaz Duque:ADCT: Consultancy; Astra Zeneca: Consultancy; Incyte: Consultancy; Morphosys: Consultancy; Epizyme: Consultancy.