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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, Joaquín Martínez-López, José González-Medina, Lucía López-Anglada, María-Teresa Cedena, Noemi Puig, Albert Oriol, María-Jesús Blanchard, Rafael Ríos, Jesús Martin, Rafael Martínez, Anna Sureda, Miguel Teodoro Hernández, Javier de la Rubia, Isabel Krsnik, Valentín Cabañas, Luis Palomera, Joan Bargay, María-Victoria Mateos, Laura Rosiñol, Jesús 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 immunofixation electrophoresis (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 to determine the uIFE-positive rate in patients who became sIFE-negative posttreatment and evaluate rates of minimal residual disease (MRD)–negative status and progression-free survival (PFS) 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 posttreatment 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 posttreatment, 3 (1.8%) were uIFE positive. Among patients achieving CR vs uCR, there were no significant differences in postconsolidation MRD-negative (<10−6; 76% vs 75%; P = .9) and 2-year PFS (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 January 25, 2019.
  • Accepted March 21, 2019.
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