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T‐cell receptor excision circles: a novel prognostic parameter for the outcome of transplantation in multiple myeloma patients

Summary. This study investigated whether T‐cell receptor excision circles (TRECs) are a prognostic marker for the outcome of myeloma patients undergoing a tandem autologous peripheral blood stem cell transplantation (PBSCT). Twenty‐five patients were enrolled. Samples were obtained at study enrolment, after conventional therapy, between first and second transplantation and 3, 6, 12 and 24 months after the second PBSCT. TRECs were quantified using real‐time polymerase chain reaction. A high variation in TREC levels was found at diagnosis (median TREC level 136/105 peripheral blood mononuclear cells (PBMCs); range 1–1729), suggesting individual differences in thymic output of naive T cells. Patients with more than 136 TRECs/105 P BMCs at diagnosis had a statistically significant better overall survival (P = 0·05) and event‐free survival (P = 0·045), whereas low TREC levels correlated with a higher incidence of infectious complications. Median TREC values were lowest after the first PBSCT (52/105 PBMCs) and reached the baseline 12 months after the second transplantation. Patients with high TREC levels after the second PBSCT had a significantly higher probability of being in complete or partial remission 30 months after the second PBSCT. TREC levels were not correlated with β2‐microglobulin and C‐reactive protein levels at diagnosis. These data suggest that TRECs could be a relevant prognostic factor for patients who receive high‐dose chemotherapy and autologous PBSCT.