Racial Differences in Treatment Dose Intensity Among Patients with Diffuse Large B-Cell Lymphoma: Analysis of the Veterans Health Administration (VHA) National Database

Introduction: Previous studies in diffuse large B-cell lymphoma (DLBCL) have demonstrated that higher treatment dose intensity is associated with improved survival. Race-based differences in dose intensity may contribute to outcome differences. In order to better understand the relationship between dose intensity and race, we performed a retrospective analysis of veterans examining demographic and clinical factors associated with dose intensity in patients with DLBCL.

Methods: Patients diagnosed with DLBCL between October 1, 1998 and December 31, 2008 and treated within the VHA system with CHOP or CHOP-like regimens (+/- rituximab) were identified in the VA Central Cancer Registry. Data on age, sex, race, stage, lactate dehydrogenase (LDH), B-symptoms, body mass index, HIV status, co-morbidities, medications, and socioeconomic status were obtained. Average relative dose intensity (ARDI) was calculated for the use of cyclophosphamide and doxorubicin in patients who received CHOP chemotherapy. Univariate analysis was performed to explore demographic and clinical characteristics dichotomized by ARDI < or ≥ 80%. Additionally, a multivariate logistic regression analysis was used to identify baseline factors associated with receiving treatment with an ARDI ≥ 80%.

Results: 1575 DLBCL patients who received doxorubicin and survived more than 5 months after treatment initiation were identified. On univariate analysis, patients who received ARDI <80% were more likely to be older (66.1 vs 61.2, p=<0.001), have advanced stage disease (58.9% vs 52.7%, p=0.015), have systemic B-symptoms (51.7% vs 45.5%, p=0.002), have more co-morbidities (mean co-morbidity score 2.4 vs 1.7, p=<0.0001), have HIV (7.5% vs 3.3%, p=0.0002), less likely to receive rituximab (73.5% vs 79.1%, p=0.008), and were more likely to be from the lowest estimated household income quartile (25.5% vs 21.8%, p=0.03). While not statistically significant on univariate analysis, patients receiving lower ARDI were slightly more likely to be Black (13.8% vs 10.6%, p=0.053). On multivariate logistic regression analysis, factors associated with reduced odds of receiving treatment with an ARDI ≥ 80% included: Black race, (OR 0.62; 95% CI 0.44 – 0.87), age (OR 0.96; 95% CI 0.95 – 0.97), HIV positive status (OR 0.24; 95% CI 0.14 – 0.40), and presence of B-symptoms (OR 0.74; 95% CI 0.59 – 0.93).

Conclusion: After controlling for the other identified variables, Black patients were significantly less likely to receive an ARDI of ≥ 80%. The reasons for this finding are unknown from this analysis. Future efforts to reduce racial outcome disparities in NHL could include efforts to understand the underlying causes of chemotherapy dose reductions and delays in racial minority populations, which were present in the VHA, an equal access healthcare system.