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Role of urine immunofixation in the complete response assessment of MM patients other than light- chain-only disease

Juan-José Lahuerta, Ana Jiménez Ubieto, Bruno Paiva, Joaquin Martinez-Lopez, José Gonzalez-Medina, Lucia Lopez-Anglada, María-Teresa Cedena, Noemi Puig, Albert Oriol, María-Jesús Blanchard, Rafael Rios, Jesús Martín, Rafael Martinez, Anna Sureda, Miguel Teodoro Hernández, Javier de la Rubia, Isabel Krsnik, Valentin Cabañas, Luis Palomera, Joan Bargay, María-Victoria Mateos, Laura Rosiñol, Jesus F. San Miguel and Joan Blade

Key Points

  • In MM patients who became sIFE-negative, 100% (serum M-protein only at diagnosis) / 98.6% (serum/urine M-protein) were also uIFE-negative.

  • Patients meeting all criteria for CR but without uIFE assessment have outcomes comparable to those in CR and superior to those with VGPR.

Abstract

Response criteria for multiple myeloma (MM) require monoclonal protein (M-protein)-negative status on both serum (sIFE) and urine (uIFE) immunofixation-electrophoresis for classification of complete response (CR). However, uIFE is not always performed for sIFE‑negative patients. We analyzed M-protein evaluations from 384 MM patients (excluding those with light-chain-only disease) treated in the GEM2012MENOS65 (NCT01916252) trial in order to determine the uIFE-positive rate in patients who became sIFE-negative post-treatment; and evaluate rates of minimal residual disease (MRD)-negative status and progression-free survival among patients achieving CR, CR but without uIFE available (uncertain CR; uCR), or very good partial response (VGPR). Among 107 patients with M‑protein exclusively in serum at diagnosis who became sIFE-negative post-treatment and who had uIFE available, the uIFE-positive rate was 0%. Among 161 patients with M‑protein in both serum and urine at diagnosis who became sIFE-negative post‑treatment, 3 (1.8%) were uIFE-positive. Among patients achieving CR versus uCR there were no significant differences in post-consolidation MRD-negative (<10-6; 76% vs. 75%, P = .9) and 2-year progression-free survival (85% vs. 88%, P = .4) rates; rates were significantly lower among patients achieving VGPR. Our results suggest that uIFE is not necessary for defining CR in MM patients other than those with light-chain-only disease.

  • Submitted March 19, 2019.
  • Revision received March 22, 2019.
  • Accepted March 21, 2019.