P43 CIRCULATING CLONAL PLASMA CELLS AT START OF SALVAGE REGIMEN PROVIDE POWERFUL PROGNOSTICATION BIOMARKER IN MULTIPLE MYELOMA PATIENTS AT FIRST RELAPSE - A. Romano; N. L. Parrinello; G. Scandura; S. Marino; A. Triolo; V. Del Fabro; F. Di Raimondo; C. Conticello (HemaSphere, 2023)