Validation of the NCCN‐IPI for diffuse large B‐cell lymphoma (DLBCL): the addition of β2‐microglobulin yields a more accurate GELTAMO‐IPI

Abstract

The study included 1848 diffuse large B‐cell lymphoma (DLBCL)patients treated with chemotherapy/rituximab. The aims were to validate the National Comprehensive Cancer Network International Prognostic Index (NCCN‐IPI) and explore the effect of adding high Beta‐2 microglobulin (β2M), primary extranodal presentation and intense treatment to the NCCN‐IPI variables in order to develop an improved index. Comparing survival curves, NCCN‐IPI discriminated better than IPI, separating four risk groups with 5‐year overall survival rates of 93%, 83%, 67% and 49%, but failing to identify a true high‐risk population. For the second aim the series was split into training and validation cohorts: in the former the multivariate model identified age, lactate dehydrogenase, Eastern Cooperative Oncology Group performance status, Stage III‐IV, and β2M as independently significant, whereas the NCCN‐IPI‐selected extranodal sites, primary extranodal presentation and intense treatments were not. These results were confirmed in the validation cohort. The Grupo Español de Linfomas/Trasplante de Médula ósea (GELTAMO)‐IPI developed here, with 7 points, significantly separated four risk groups (0, 1-3, 4 or ≥5 points) with 11%, 58%, 17% and 14% of patients, and 5‐year overall survival rates of 93%, 79%, 66% and 39%, respectively. In the comparison GELTAMO IPI discriminated better than the NCCN‐IPI. In conclusion, GELTAMO‐IPI is more accurate than the NCCN‐IPI and has statistical and practical advantages in that the better discrimination identifies an authentic high‐risk group and is not influenced by primary extranodal presentation or treatments of different intensity.