Outcome of Diffuse Large B Cell Lymphoma in the VA System: The Rituximab Era.

Background: Addition of rituximab to chemotherapy in patients with diffuse large B cell Lymphoma (DLBCL) has been shown to improve survival in several recent clinical studies. A study from British Columbia confirmed those results in a population-based cohort. No similar population based studies were conducted in the USA. Our study aims to address outcome of DLBCL in the era of rituximab in the VA health system.

Methods: This was a retrospective analysis. The VA Central Cancer Registry (VACCR) database was used to identify patients with DLBCL diagnosed between 1995 and 2005. There are approximately 120 VA medical centers diagnosing and/or treating patients with cancer. The VACCR aggregates the data collected by the medical centers’ cancer registries. Data were extrapolated and analyzed using bio-statistical software SPSS. Variables included age, sex, stage of disease, histology subtype, date of diagnosis, date of last contact, date of relapse, vital status, whether patients received chemotherapy and or radiation. Use of rituximab was not specifically recorded in the registry. Due to that we divided the patients into two groups, patients diagnosed with DLBCL before 2001 (pre rituximab era group) and patients diagnosed after 2001 (rituximab era group). The initial results of rituximab in DLBCL were presented in 2000 and published in January 2002. Independent t test was used for comparing continuous variables and chi square test for categorical variables. Wilcoxon test was used to compare survival among the two groups.

Results: There were 2792 patients with DLBCL at the VACCR between 1995 and 2005, 1772 patients in pre rituximab era and 1020 patients in the rituximab era. The mean age at diagnosis was to 64 in pre rituximab group and 66 in rituximab group (P-value 0.015). Race distribution was similar between the two groups. More patients were diagnosed at advanced stage (stage III and IV) 61 % in rituximab group compared to 57% in pre rituximab group (P-value <0.005), IPI score data were not available. More patients in pre rituximab era did not receive multi-agent chemotherapy 28% versus 22% (P-value < 0.005). More patients received radiation 21 % in pre rituximab group compared to 16% in rituximab era group (P-value < 0.005). The 5-year overall survival was 26% in pre rituximab era and 36% after rituximab (P-value 0.0025). Using Cox regression multivariable analysis age, use of mutli-agent chemotherapy, radiation and whether patients were diagnosed and treated before or after 2001 were statistically significant independent variables affecting survival.

Conclusions: Overall survival of DLBCL in VA patients had improved in the rituximab era. The magnitude of improvement observed in this study is similar to what was described in previous studies. Other factors contributing to improvement in outcomes such as supportive care could not be differentiated in this study. This is a population-based study suggesting improvement in survival in DLBCL in the rituximab era.