Non-IgM Secreting Lymphoplasmacytic Lymphoma - Experience of a Reference Center for Waldenstrom Macroglobulinemia

Abstract Background: Lymphoplasmacytic lymphoma (LPL) secreting immunoglobulins other than IgM is rare. Therefore, there are very few case series on non-IgM LPL and little is known about the clinical features and outcomes of patients with this disease. Aim: To describe disease characteristics and clinical outcomes of patients with non-IgM LPL. Methods: We identified cases of non-IgM LPL in the records of the Waldenström Macroglobulinemia (WM) clinic at our institute, between the years of 2000-2018. All patients were part of the clinic's registry. We extracted data from their electronic records and included only cases with centrally-confirmed diagnosis. Response assessment was based on 6th IWWM criteria. Time to events was estimated using the Kaplan-Meier method. Results: We found 31 patients with non-IgM LPL. Median age at diagnosis was 63 years (range, 37-83 years), 45% were over the age of 65, and 65% were women. The paraprotein secreted by these tumors was IgG in 20 cases (65%); IgA in 5 (16%), light-chain (LC) in 2 (6%) and was non-secretory (NS) in 4 (13%). Median level of IgG and IgA at diagnosis was 3,967 mg/dl (range, 804-8,006 mh/dl) and 1,980 mg/dl (range, 1,020-6,210 mg/dl), respectively. We included 5 cases with concurrent IgM paraproteinemia, when it was clearly secreted to a lesser extent than dominant immunoglobulin and had similar LC restriction. Five patients had MGUS preceding diagnosis of LPL. Presenting symptoms were anemia-related (n=13), asymptomatic (n=7), neuropathy, autoimmune phenomena, elevated creatinine, bleeding diathesis and recurrent infections (n=3, each). Only 1 patient had B-symptoms. One patient with IgA LPL and serum IgA level of 4,000 mg/dl presented with retinal vein occlusion due to hyperviscosity. Non-bulky (<5 cm) lymphadenopathy was found in 11 patients (35%), and mild splenomegaly in 5 (16%). Anemia was prevalent (53%) with hemoglobin <10 g/dl in 23%. No patient had neutropenia (ANC <1 K/uL) or thrombocytopenia (platelets <100 K/uL) at presentation. Five patients (16%) presented with mild lymphocytosis (median, 7.1 K/uL; range, 3.3-20.6 K/uL). Βeta-2-microglobulin level was >3 mg/L in 48% of available patients (n=12/24). All bone marrow biopsies showed that malignant cells were positive for CD20 and CD19 by flow cytometry; 14% were CD5 positive (subset/dim); 29% CD23 partially-positive; and all were CD10 negative. Five of 19 cases (26%) had cytogenetic abnormalities, but apart from del6q (n=1), none were of commonly known aberrations in hematological malignancies. Only 1 patient with kidney disease underwent renal biopsy that revealed light-chain deposition disease. Amyloidosis was detected in 2 patients, one with neuropathy and the other patient was asymptomatic. The MYD88 L265P mutation was detected in 10 of 14 patients (71%) tested, and CXCR4 mutations in 2 of 8 patients (25%) tested. Both patients with a CXCR4 mutation needed treatment immediately at diagnosis and subsequently had 4 or more lines of therapy. With a median follow up of 4.6 years (95% CI 2.5-7.6 years), 68% of the patients had been treated (n=21), 90% of whom within the first year from diagnosis. As such, the median time to first treatment was 2.3 months. However, time to next therapy was significantly longer, with a median of 4.7 years. Patients had a median of 3 lines of therapy (range, 1-8), including purine analogues in 33% of patients, alkylating agents in 48%, bendamustine in 38%, anti-CD20 monoclonal antibodies in 90%, proteasome inhibitor in 24%, and immunomodulating drugs in 14%. Two patients received ibrutinib: one achieved VGPR with over 3 years remission duration, after prior 7 lines of therapy; and the other, who had only a brief response, was found to carry the CXCR4 mutation. There were 4 (13%) deaths: 1 patient developed Bing-Neel syndrome at first relapse that ultimately lead to his demise; 1 died from treatment complications; and 2 of unknown cause. The 5-year and 10- year OS are 90% (95% CI 64-98%) and 81% (95% CI 49-94%), respectively (Figure 1). Conclusion: To our knowledge, this is the largest reported series of non-IgM LPL and the first to demonstrate excellent long-term outcomes in these patients. Figure 1. Figure 1. Disclosures Hunter: Pharmacyclics: Consultancy. Treon:Janssen: Consultancy, Other: Travel, Accommodations, Expenses; BMS: Research Funding; Johnson & Johnson: Consultancy; Pharmacyclics: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding. Castillo:Beigene: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Genentech: Consultancy; Millennium: Research Funding.