A multicentre prospective phase <scp>II</scp> study of rituximab combined with bortezomib, lenalidomide and dexamethasone, followed by lenalidomide maintenance (R‐ <scp>VRD</scp> ) in patients with Waldenström's macroglobulinaemia ( <scp>KMM1803</scp

Waldenström's macroglobulinaemia (WM) has heterogeneous clinical features and limited standard therapeutic options. Although rituximab-based combinations and Bruton's tyrosine kinase inhibitors have improved outcomes, challenges like incomplete responses and toxicity remain. This prospective, multicentre, phase II study evaluated the efficacy and safety of rituximab, bortezomib, lenalidomide and dexamethasone (R-VRD) induction therapy, followed by lenalidomide maintenance in patients with symptomatic WM. Two-year progression-free survival (PFS) was the primary end-point, and the secondary end-points included overall response rate (ORR), overall survival (OS) and safety. Thirty-eight patients (median age: 66 years) were enrolled. The ORR was 81.6%, and 18.4% of the patients achieved a complete response (CR). The estimated 2-year PFS and OS rates were 57.9% and 94.7%, respectively, after a median follow-up of 38.5 months. Notably, responses deepened during lenalidomide maintenance, and 16 experienced further response improvement during the maintenance phase. The most common adverse events were Grade 3-4 haematological toxicities, particularly neutropenia, but they were manageable. Peripheral neuropathy and rash were generally mild. Patients achieving a CR showed no disease progression within 2 years, emphasizing the deep responses' prognostic value. R-VRD induction, followed by lenalidomide maintenance, demonstrated high efficacy and an acceptable safety profile against symptomatic WM.