Tumor load in patients with multiple myeloma: β₂‐microglobulin levels versus low‐dose whole‐body CT

Objective Beta‐2‐microglobulin is a serum marker of tumor burden in multiple myeloma (MM). Our aim was to correlate serum β₂‐microglobulin levels in patients with MM to tumor burden determined by low‐dose whole‐body CT (LDWBCT). Materials and Methods A total of 52 patients with newly diagnosed, untreated MM who underwent LDWBCT were included. LDWBCT scans were assessed by two musculoskeletal radiologists in consensus for focal lesions. The Durie and Salmon PLUS staging system was used for staging patients in stages I‐III. β₂‐microglobulin was also subdivided into stages I‐III on the basis of the multiple myeloma International Staging System (ISS). Results Using the Durie and Salmon PLUS staging system criteria for image evaluation, we were able to identify stage I MM in 17 patients, stage II MM in nine patients, and stage III MM in 26 patients. Eight of nine patients with stage II MM and 16 of 26 patients with stage III MM had normal β₂‐microglobulin levels. Thus, 24 of 35 patients (68.6%) had 5 or more focal lesions and false‐negative β₂‐microglobulin levels. Conclusion Serum β₂‐microglobulin levels alone may not indicate the full extent of tumor burden in a significant subset of myeloma patients.