Radiat Oncol J.  2020 Jun;38(2):129-137. 10.3857/roj.2019.00570.

The predictive value of serum myeloma protein in solitary plasmacytoma

  • 1Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea
  • 2Department of Radiation Oncology, Konkuk University Medical Center, Seoul, Korea
  • 3Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
  • 4Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, Korea
  • 5Cancer Research Institute, Seoul National University, Seoul, Korea
  • 6Department of Radiation Oncology, Seoul National University Bundang Hospital, Seongnam, Korea


To identify the clinical usefulness of serum M protein and to establish a rationale for regular follow-up with serum protein electrophoresis in solitary plasmacytoma.
Materials and Methods
Sixty-nine patients with solitary plasmacytoma and solitary plasmacytoma with minimal marrow involvement according to the International Myeloma Working Group criteria were retrospectively reviewed.
At a median follow-up of 6.2 years, 5-year local control (LC), 5-year multiple myeloma-free survival (MMFS), 5-year failure-free survival (FFS), and 5-year overall survival (OS) were 82.6%, 44.1%, 41.8%, and 85.1%, respectively. Among the patients whose initial serum M protein was present or not evaluated, 37.3% of patients showed disappearance of serum M protein after various treatment. MMFS of these patients were comparable to non-secretory plasmacytoma with undetectable levels of M protein, and significantly better than patients with persistent M protein. Increase of serum M protein ≥0.1 g/dL was most predictive of treatment failure with area under the curve of 0.731.
Patients who eventually showed persistence of serum M protein after treatment showed worse MMFS and FFS compared to those whose serum M protein disappeared or who had initially non-secretory disease. The increase of serum M protein level ≥0.1 g/dL from current nadir was predictive of treatment failure. Therefore, regular follow-up with serum M protein is highly recommended especially unless the patient had initially non-secretory disease.


Solitary plasmacytoma; Myeloma proteins; Risk factors; Radiation therapy
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