The International Staging System for Multiple Myeloma is Applicable in Symptomatic Waldenstrom's Macroglobulinemia

Several studies have indicated that age, hemoglobin and serum albumin are among the most important prognostic factors for survival of patients with Waldenstrom's macroglobulinemia (WM). Furthermore, recent data indicate that serum b2-microglobulin may be also significant. The recently proposed International Staging System (ISS) for multiple myeloma is based on serum albumin and b2-microglobulin. We designed a study to assess this model in patients with WM. Our analysis included 83 previously untreated patients with WM who required systemic treatment and in whom pretreatment values for both serum albumin and b2-microglobulin were available. Based on these variables the patients were stratified into three ISS stages. Stage I: albumin > or = 3.5 g/dl and b2-microglobulin < 3.5 mg/dl, stage II: albumin < 3.5 g/dl and b2-microglobulin < 3.5 mg/gl or b2-microglobulin 3.5-5.5 mg/dl and stage III: b2-microglobulin > 5.5 mg/dl. Low albumin (< 3.5 g/dl) and high b2-microglobulin (> or = 3.5 mg/dl) were recorded in 45% and 52% of patients respectively. The distribution of patients in the three ISS stages was: stage I: 30%, stage II: 43% and stage III: 27%. The median overall survival from the date of treatment initiation was 115 months. The median survival according to ISS was not reached for stage I, 116 months for stage II and 54 months for stage III (P = 0.02). Our analysis indicated that the recently proposed ISS for multiple myeloma could stratify the patients with WM into three distinct subgroups with significantly different survival times. If this model is validated in independent series, it could provide a new staging system for WM based on readily available and reproducible variables.