TNFRSF17 and plasma cell myeloma: The concentration of BCMA in serum, a peripherally accessible and composite marker of change in myeloma tumor burden, was significantly greater in patients with myeloma who had progressive disease as best overall response compared with those achieving a response of PR or better to ide-cel, and changes in levels of circulating soluble BCMA (sBCMA) in serum were correlated with changes in an individual patient’s clinical status15.