Prognostic significance of the serum phosphorus level and its relationship with other prognostic factors in multiple myeloma

We studied the serum phosphorus (P) level of 110 patients with multiple myeloma (MM) (age range 42–83 years, median 62 years) and evaluated the relationship between that and other prognostic factors. Serum P level significantly correlated with the prognostic factors that are relevant to renal dysfunction: serum creatinine (P<0.00000001), serum β2-microglobulin (P=0.00000088), serum uric acid (P=0.0000014), and corrected serum calcium (cCa P=0.000067). Although it also correlated with the percentage of plasma cells in bone marrow nucleated cells (BMPC%) and the hemoglobin (Hb) and leukocyte counts, the significance was less than for the other four prognostic factors. Serum creatinine, BMPC%, leukocyte count, serum uric acid, bone lesions, β2-microglobulin, and serum cCa were all significantly higher and Hb significantly was lower in the MM patients with hyperphosphatemia (serum P>3.8 mg/dl). The survival time was significantly shorter in these patients (P=0.000087). Multivariate analysis (Cox’s proportional hazards regression model) showed that the serum P level is a significant negative prognostic factor in MM patients.