Race and Socioeconomic Factors Influencing Treatment Disparities and Comparative Effectiveness in Very Elderly Patients with Diffuse Large B-Cell Lymphoma

Purpose

Clinical trials for treatment of diffuse large B-cell lymphoma (DLBCL) exclude the very elderly, ages 80 years and older. Treatment differences by race/ethnicity in very elderly DLBCL patients may result from disparities in health care access and other socioeconomic factors, but it remains unclear whether disparities in treatment lead to poorer survival. Our purpose was to (1) examine differences in utilization of chemotherapy and immunotherapy for DLBCL in very elderly patients and (2) characterize the comparative effectiveness of these treatments for all-cause and cancer-specific mortality in this population.

Patients and Methods

We conducted a retrospective cohort study of very elderly patients ages 80 years and older diagnosed with first primary DLBCL between 2001-2011 from the Surveillance Epidemiology and End Results (SEER)-Medicare linked database. Patients were included if they had at least 12 months of continuous enrollment on Medicare Parts A and B prior to and following diagnosis.

Using SEER-Medicare administrative claims, we determined types of primary DLBCL treatment (e.g., observation, radiation, chemotherapy and immunotherapy). We also collected information on cancer stage, clinical characteristics, comorbid conditions and census tract level sociodemographic data. We used multivariable logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (CI) for likelihood of being treated with chemotherapy/immunotherapy. We examined possible differences in risk of all-cause and cancer-specific mortality by race and ethnicity using Cox proportional hazards models to account for differences in treatment. We also estimated hazard ratios (HR) and 95% CIs to determine the comparative effectiveness of rituximab-based combination chemotherapy for these mortality endpoints by racial/ethnic group.

Results

Among 4,404 very elderly DLBCL patients, the median age was 84 years (interquartile range: 82-87) and more patients included in the analysis were female (59%), non-Hispanic White (86%) and slightly more advanced stage at diagnosis (Ann Arbor stages III-IV, 51%). Forty five percent of patients received infused chemotherapy and/or immunotherapy. Of those treated patients, 77% received rituximab plus combination chemotherapy, either CHOP or CVP. Greater proportions of Black (63%) and Hispanic (63%) patients were not treated with chemotherapy/immunotherapy compared to White patients (54%). The observed treatment disparities were not significant after accounting for sociodemographic variables including Medicare supplementation and census tract poverty level (Black vs. White: OR=0.72, 95% CI 0.43-1.22; Hispanic vs. White: OR=1.04, 95% CI 0.72-1.49). No differences were observed in all-cause or cancer-specific mortality by race/ethnicity. When analyzing the comparative effectiveness of rituximab combination therapy in these populations, the benefit of treatment in all-cause mortality was equal or greater in Black (HR=0.28, 95% CI 0.16-0.50) and Hispanic (HR=0.22, 95% CI 0.15-0.34) patients compared to White patients (HR=0.33, 95% CI 0.30, 0.36); similar results were found for reduced cancer-specific mortality in Black (HR=0.14, 95% CI 0.07-0.31), Hispanic (HR=0.20, 95% CI 0.12-0.34) and White patients (HR=0.28, 95% CI 0.25-0.32).

Conclusions

In this population-based sample of very elderly Medicare beneficiaries with DLBCL, we observed low rates of treatment with systemic therapy. Racial/ethnic differences in treatment utilization were explained by socioeconomic factors. When accounting for these factors, we demonstrated no differences in risk of all-cause or cancer-specific mortality by race/ethnicity and similar effectiveness of treatment across racial/ethnic groups. Determining barriers to access for highly effective DLBCL therapies in the very elderly, particularly for racial and ethnic minorities, is of public health importance.