The importance of bone marrow examination in determining complete response to therapy in patients with multiple myeloma

Abstract

The current definition of complete response in multiple myeloma includes a requirement for a bone marrow (BM) examination showing less than 5% plasma cells in addition to negative serum and urine immunofixation. There have been suggestions to eliminate the need for BM examinations when defining complete response. We evaluated 92 patients with multiple myeloma who achieved negative immunofixation in the serum and urine after therapy and found that 14% had BM plasma cells more than or equal to 5%. Adding a requirement for normalization of the serum-free light chain ratio to negative immunofixation studies did not negate the need for BM studies; 10% with a normal serum-free light chain ratio had BM plasma cells more than or equal to 5%. We also found that, on achieving immunofixation-negative status, patients with less than 5% plasma cells in the BM had improved overall survival compared with those with 5% or more BM plasma cells (6.2 years vs 2.3 years, respectively; P = .01).

Figure 1

Kaplan-Meier curve showing survival (in years) from diagnosis of patients with true CR (negative serum and urine IFE and < 5% BM plasma cells) compared with patients with negative serum and urine IFE but 5% or more BM plasma cells.

Figure 2

Kaplan-Meier curve showing survival (in years) after achieving negative serum and urine IFE of patients with less than 5% BM plasma cells (true CR patients) compared with patients with 5% or more BM plasma cells.