Transformation and survival in patients with Waldenström macroglobulinemia: a population-based study

Background Waldenström’s macroglobulinemia (WM) is a rare hematologic neoplasm characterized by an indolent clinical course. However, a significant proportion of patients undergo histological transformation to aggressive diffuse large B-cell lymphoma (DLBCL). Long-term population-based data on the transformation and survival are scarce. Based on the Surveillance, Epidemiology, and End Results (SEER) database, we performed this study to estimate the risk of transformation and outcomes of patients with WM. Methods 8191 patients with WM were retrieved from the SEER database. Competing risk methods were employed to evaluate the cumulative incidences and putative risk factors for transformation. Survival outcomes were analyzed using Kaplan-Meier and Cox proportional hazards regression. Results The cumulative incidence rates for transformation at 5 and 10 years were 1.0% (95% CI, 0.8%–1.3%) and 1.9% (95% CI, 1.5%–2.2%), respectively. A substantial increase in total mortality was related to the time-dependent transformation (HR, 4.21 [95% CI, 3.36–5.26]; P < 0.001). Patients who presented with transformation > 24 months after WM diagnosis had a longer overall survival (OS) than those who experienced transformation within 24 months (5-year rate, 81.9% [95% CI, 74.7%–89.9%] v 42.7% [95% CI, 26.4%–69.2%]; P < 0.001). The OS was shorter for patients with DLBCL transformed from WM than for those with matched de novo DLBCL (5-year rate, 28.0% [95% CI, 20.5%–38.1%] v 49.5% [95% CI, 41.2%–59.4%]; P = 0.001). Conclusions Histological transformation to DLBCL was associated with significantly increased mortality in patients with WM, and the survival outcomes substantially worse than matched de novo DLBCL cases.