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

Summary 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.