Predictive factors for response to rituximab in Waldenstrom's macroglobulinemia.

Rituximab is an active agent for the treatment of Waldenstrom's macroglobulinemia. However, many patients do not respond to this agent and several others develop secondary resistance. In order to identify clinical and laboratory parameters that could predict a higher likelihood for response, we evaluated 54 patients who were treated with single-agent rituximab. Twenty-four patients (44%)exhibited > or = 50% reduction of serum monoclonal protein. Previously untreated and pretreated patients had the same probability for response. Low response rates were noted in patients with serum monoclonal protein level > or = 40 g/L (17%) and serum albumin level < 35 g/L (14%). Furthermore, a multivariate analysis indicated that high serum monoclonal protein and low albumin were the dominant variables associated with shorter time to progression. The presence of 2, 1, or none of these variables was associated with median times to progression of 4 months, 11 months, and approximately 48 months, respectively. We conclude that patients with low levels of monoclonal protein and normal albumin are the best candidates for treatment with rituximab.

Treatment of Waldenstrom's macroglobulinemia with rituximab: prognostic factors for response and progression.

Recent data have suggested that rituximab is an active agent for the treatment of Waldenstrom's macroglobulinemia (WM). However, the patients that are more likely to benefit have not been clearly defined. In order to address this question we evaluated 52 patients who were treated with single-agent rituximab in the context of prospective studies. Several clinical and laboratory variables were assessed for their correlation with response and time to progression. Twenty-three (44%) patients achieved a partial response after treatment with rituximab. Previously untreated and pretreated patients had the same probability for response. Higher response rates were noted in patients with serum monoclonal protein < 40 g/l, with serum albumin > or = 35 g/l and with kappa light chain. The median time to progression for all patients was 13.8 months. A multivariate analysis indicated that elevated serum monoclonal protein levels and low serum albumin were the dominant variables associated with shorter progression. Presence of two, one or none of these adverse prognostic factors was associated with time to progression of 3.6 months, 11 months and more than 40 months, respectively. We conclude that rituximab is an effective treatment modality for patients with WM. Patients with both low levels of monoclonal protein and normal albumin are the best candidates for treatment with standard dose rituximab.