Survival From Time Of Transformation In Patients With Transformed Lymphoma At Time Of Diagnosis.

e20054 Background: Histologic transformation (HT) to aggressive lymphoma can occur in indolent lymphoma and is considered to convey poor prognosis. Most data come from follicular lymphoma (FL). We conducted a retrospective analysis to compare outcomes of transformed marginal zone lymphoma and lymphoplasmacytic lymphoma (tMZL/LPL) with those of transformed FL (tFL). Methods: We collected data from patients diagnosed with HT between 2000 and 2018. Transformed CLL was excluded. Survival estimates were done with the Kaplan Meier method; comparisons were done with log-rank test. The effect of covariates on OS was evaluated with Cox proportional hazards method. Results: We identified 87 pts (58 tFL, 29 tMZL/LPL). There were no differences in baseline characteristics, except for COO subtype by Hans criteria and circulating IgM. There were no differences in OS or EFS based on the underlying lymphoma subtype (OS: tFL = 60.1m vs. tMZL/LPL = 64.8m, p = 0.53; EFS: tFL = 25.2m vs. tMZL/LPL = 27.6m). Univariate and multivariate analyses identified age at HT (HR for age > 60 = 3.5, 95% CI: 1.7-7.6), poor performance status (HR for ECOG ≥3 = 23, 95% CI: 7.3-70) and having a previous diagnosis of indolent lymphoma (HR for previous diagnosis = 3.7, 95% CI: 1.87-7.4) as adverse risk factors for OS after HT. Pts with previous diagnosis of indolent lymphoma with subsequent HT had inferior OS than pts presenting first with HT (median OS 25m vs. not reached, p < 0.0001); EFS (median EFS for treated pts = 11m vs. 49m). Conclusions: Underlying lymphoma does not affect OS after HT and long term survival can be achieved in pts who receive treatment. tMZL/LPL is more frequently of non-GCB origin has monoclonal IgM. Pts who present with HT as their first lymphoma-related event have better OS. These findings will lead to further exploration of the genetic changes that occur at the time of transformation of indolent lymphomas. [Table: see text]