Addition of tumor bulk to the International Prognostic Index (IPI) does not improve prognostication in diffuse large B-cell Lymphoma (DLBCL)

Abstract

7585 Background: Bulky disease in DLBCL has been linked to adverse outcomes. Tumor bulk was not included in the IPI due to lack of uniform data availability. Radiation to sites of bulky disease may result in improved outcomes. We evaluated the impact of tumor bulk as a prognostic factor combined with the IPI in predicting overall survival in DLBCL. Methods: A retrospective review of adult patients with newly diagnosed DLBCL from October 1982 through February 2000 was done, and data pertaining to tumor size, age, Ann Arbor stage, performance status (PS), lactate dehydrogenase level (LDH), extranodal involvement, radiation therapy and overall survival was collected. Surviving patients were followed through December 2005. Bulky disease was defined as largest tumor mass of ≥10 cm. Statistical analysis was performed using Cox proportional hazards regression. Results: Complete data was available on 669 patients. All patients received anthracycline or mitoxantrone based chemotherapy. Bulky disease was found in 27% of patients, while radiation was employed in 22% of patients. There was no significant association between use of radiation and tumor bulk. IPI was calculated as low risk—37%, low-intermediate—28%, high-intermediate—20% and high—14%. Median follow-up of survivors was 100 months (range <1 - 263). In univariate analysis, bulky disease alone was a significant predictor of inferior survival (RR 1.27, p = 0.044), however when combined with the IPI it was not a significant predictor of poorer overall survival as compared with non-bulky disease (RR 1.10, p = 0.36). Radiation therapy was associated with a significant increase in overall survival (RR 0.70, p = 0.005). Conclusions: Bulky disease is an important independent prognostic factor for overall survival in patients with DLBCL, however when combined with IPI it does not result in improved prediction. It is unclear whether this is due to insufficient power or due to possible inter-relation between tumor size, LDH and PS, the latter of which are included in the IPI. Radiation therapy to some patients with bulky disease may also have mitigated the adverse effect. Larger prospective studies may shed light on the utility of tumor bulk combined with IPI and possible alterations in management. No significant financial relationships to disclose.