International prognostic Index (IPI) is the most widely used clinical prediction model for diffuse large B-cell lymphoma (DLBCL) patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP), but may be suboptimal in older patients. We aimed to develop and externally validate a clinical prediction model for older, R-CHOP treated DLBCL patients by examining geriatric assessment and lymphoma-related parameters in real-world cohorts.
A population-based training set of 365 R-CHOP treated DLBCL patients ≥70 years was identified through the Cancer Registry of Norway. The external test set consisted of a population-based cohort of 193 patients. Data on candidate predictors was retrieved from the Cancer Registry and through review of clinical records. Cox regression models for 2-year overall survival (OS) were used for model selection.
Activities of daily living (ADL), Charlson Comorbidity index (CCI), age, sex, albumin, stage, ECOG and LDH were identified as independent predictors and combined into a Geriatric prognostic index (GPI). The GPI demonstrated good discrimination (optimism-corrected C-index 0.752), and identified a low-, intermediate- and high-risk group with significantly different survival (2-year OS 94%, 65%, 25%). At external validation, the continuous and grouped GPI demonstrated good discrimination (C-index 0.727, 0.710) and the GPI groups had significantly different survival (2- year OS 95%, 65%, 44%). Both the continuous and grouped GPI showed better discrimination than IPI, R-IPI and NCCN-IPI (C-index 0.621, 0.583, 0.670)
We have developed and externally validated the GPI for older DLBCL patients treated with RCHOP that outperformed IPI, R-IPI and NCCN-IPI. A web-based calculator is available at https://wide.shinyapps.io/GPIcalculator/.
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