Low levels of von Willebrand markers associate with high serum IgM levels and improve with response to therapy, in patients with Waldenström macroglobulinaemia (2018)

Waldenström macroglobulinaemia (WM) is a rare lymphoma characterized by the accumulation of malignant IgM-secreting lymphoplasmacytic cells in the bone marrow and other organs (Swerdlow et al, 2016). Recurrent MYD88 and CXCR4 mutations define the genomic landscape of WM (Hunter et al, 2017). Acquired von Willebrand disease (VWD) has been described in patients with WM (Mazurier et al, 1980), and a retrospective study suggested that high von Willebrand factor (VWF) levels might be prognostic in patients with WM (Hivert et al, 2012). However, the clinical characteristics and outcomes to therapy of WM patients with low levels of VWF antigen (VWF:Ag), VWF activity (Ristocetin cofactor; VWF:RCo) and factor VIII (FVIII) have not been extensively studied. We carried a retrospective study in newly diagnosed WM patients seen at our institution who were tested for VWF:Ag, VWF:RCo and FVIII levels (VW markers). Low VW markers levels were defined as below 50%. Logistic regression models were fitted to evaluate the association of clinical factors and low VW markers. We also evaluated the association of response to therapy on VW markers using linear regression models. Categorical response to therapy was defined using current guidelines (Owen et al, 2013). MYD88 mutation was evaluated using polymerase chain reaction techniques and CXCR4 mutations using Sanger sequencing (Hunter et al, 2014; Xu et al, 2014). MYD88 and CXCR4 genotyping has been routinely performed at our centre since 2013, but it is not available in all patients. A total of 320 WM patients were tested due to reported signs of bleeding or easy bruising, of whom 49 (15%) showed low levels of VW markers. The median serum IgM level in patients with low VW markers was 56·6 g/l (range 18–103 g/l) and 22·7 g/l (range 0·25–110 g/l) in patients with normal VW markers (P < 0·001). Patients with low VW markers were more likely to have serum IgM levels 30–59·99 and ≥60 g/l (Table 1). In the univariate logistic regression analysis, serum IgM level 30–59·99 and ≥60 g/l were associated with increased odds of low VW markers. In the multivariate logistic regression analyses, only serum IgM levels 30–59·99 and ≥60 g/l were independently associated with increased odds of low VW markers (Table 1). In the subset of patients who had genomic testing (n = 125), patients with low VW markers were more likely to carry CXCR4 mutations (77% vs. 37%, P < 0·001) than patients with normal VW markers. Of these, 44 patients (77%) had nonsense (NS) and 13 (22%) had frameshift (FS) mutations. Univariate analysis associated CXCR4 mutations with higher odds of low VW markers (odds ratio [OR] 5·59, 95% confidence interval [CI] 2·06–15·2, P = 0·001). The odds of VWD were higher in CXCR4 NS-mutated patients (OR 7·85, 95% CI 2·81–22·0; P < 0·001) than on CXCR4 FS-mutated patients (OR 0·86, 95% CI 0·09–7·81; P = 0·89). After adjusting for serum IgM level, CXCR4 mutations were independently associated with higher odds of low VW markers (OR 4·07, 95% CI 1·31–12·7, P = 0·016), and CXCR4 NS patients had higher odds of VWD (OR 4·67, 95% CI 1·46–14·9; P = 0·01) than CXCR4 FS patients (OR 1·24, 95% CI 0·10–14·8; P = 0·86). Of 18 patients with low VW markers who received therapy for WM, six patients (33%) received proteasome inhibitors/rituximab, 5 (28%) alkylators/rituximab, 5 (28%) ibrutinib and 2 (11%) rituximab alone. At best response, the median serum IgM level decreased, from 62·41 g/l (range 33·47–103 g/l) to 22·74 g/l (range 4·06–61 g/l), the median VWF:Ag level had increased, from 21% (range 5–49%) to 64% (range 15–200%), the median VWF:RCo level had increased, from 23% (range 9–41%) to 58% (range 19–196%), and the median FVIII level had increased, from 21% (9–43%) to 57% (30–183%) (P < 0·001 for all comparisons). Linear regression models associating change in serum IgM and change in VW markers are shown in Fig 1. The association between change in serum IgM and change in VW markers remained significant after adjusting for baseline VWF:Ag, VWF:RCo and FVIII levels, and after removing outlier observations (data not shown). Three patients (17%) achieved very good partial response (VGPR), 6 (33%) partial response (PR), 8 (44%) minor response (MR) and 1 (11%) stable disease. After therapy, 14 patients (78%) had normalized VW markers. In patients achieving VGPR, PR and MR, changes in serum IgM were −90%, −66% and −34%, while VWF:Ag changes were +700%, +225% and +95%, VWF:RCo changes were +427%, +173% and +102%, and FVIII changes were +650%, +261% and +95%, respectively (P < 0·001 for trend in each category). Our study shows that 15% of WM patients tested had low VW markers. Given that not all patients were tested, the incidence reported here is probably an overestimate. Our study suggests that low VW markers were associated with higher serum IgM levels. However, not all patients with high IgM levels had low VW markers, suggesting that the development of low VW markers is not purely dependent on IgM levels. Therefore, other factors must contribute to the development of low VW markers in WM patients, such as selective VWF adsorption on malignant cells, increased VWF proteolysis, production of anti-VWF antibodies and VWF and FVIII activation associated with increase in serum viscosity due to increased serum IgM level, or there could be interactions between VWF and FVIII with the IgM molecule itself (Michiels et al, 2001). In a subset analysis, we identified increased odds of low VW markers in patients with CXCR4 mutations. We had previously showed that CXCR4 mutations were associated with hyperviscosity (Gustine et al, 2017). In the present study, CXCR4 mutations were associated with 4-fold increased odds of low VW markers after adjusting for serum IgM levels. This finding deserves attention as it could have therapeutic implications. Ibrutinib is the only medication approved for the treatment of WM. In WM patients with CXCR4 mutations, however, responses are slower and more superficial (Treon et al, 2015). Ibrutinib affects platelet aggregation and could increase the risk of bleeding in WM patients with low VW markers. We recommend screening for VW markers in WM patients with complaints of easy bruising or mucocutaneous bleeding. Finally, our study shows that response to therapy improves VW markers in WM patients. The degree of improvement correlates with the depth of the response. Parts of this research were presented at the 59th Annual Meeting of the American Society of Hematology in Atlanta, GA. Dr. Castillo acknowledges the support of the WMR Fund. JJC designed the study, analysed the study data and wrote the manuscript. JJC, TD, PS and SPT provided treatment and follow-up for patients on the study. JNG and KM collected the study data. ZRH, GY and LX performed genotyping for MYD88 and CXCR4 mutations. All authors read, critically reviewed and approved the final manuscript. JJC has received research funds and honoraria from Abbvie, Gilead, Janssen, Millennium and Pharmacyclics. SPT has received research funds and honoraria from Janssen and Pharmacyclics. All other authors have no conflicts of interest to disclose.