Table 3.
Comparison of baseline features among patients with plasma cell dyscrasias who would be considered MGUS if no baseline bone marrow or advanced imaging.
| Variable | MM without CRAB/FLC (n = 29) | MGUS-like SMM (n = 314) | MGUS with BM (n = 1024) | p value |
|---|---|---|---|---|
| Age, median (IQR) | 61 (54–69) | 66 (57–72) | 66 (57–74) | 0.12 |
| Male, % | 45 | 61 | 61 | 0.21 |
| Isotype: IgG/IgA/LC/other, % | 59/21/21/0 | 71/19/5/6 | 66/10/7/17 | <0.0001 |
| Serum M-spike, g/dL, median (IQR) | 0.8 (0–1.8) | 1.6 (0.9–2.2) | 0.4 (0–0.9) | <0.0001 |
| M-spike category, n (%) | <0.0001 | |||
| ≤1 g/dL | 16 (57) | 92 (29) | 767 (79) | |
| 1 < g/dL ≤ 2 | 8 (29) | 122 (39) | 170 (18) | |
| >2 g/dL | 4 (14) | 100 (32) | 30 (3) | |
| Missing | 1 | 0 | 57 | |
| Light chain type | 0.82 | |||
| Kappa | 17 (59) | 187 (60) | 587 (59) | |
| Lambda | 11 (38) | 121 (39) | 402 (40) | |
| Nil | 1 (3) | 4 (1) | 14 (1) | |
| Involved sFLC level, median (IQR), g/dL | 13.5 (3.5–47.8) | 7.9 (2.9–22.7) | 2.9 (1.8–6.0) | <0.0001 |
| sFLC ratio, median (IQR) | 17.9 (3.7–71.0) | 6.9 (2.4–28.7) | 1.7 (1.1–3.6) | <0.0001 |
| SFLC ratio > 20, n (%) | 12 (52) | 78 (32) | 41 (7) | <0.0001 |
| Missing | 4 | 67 | 444 | |
| BMPCs, median % (IQR) | 20 (13–60) | 16 (11–25) | 3 (2–5) | – |
| Albumin, g/dL, median (IQR) | 3.6 (3.2–3.8) | 3.5 (3.2–3.7) | 3.4 (3.0–3.7) | 0.0002 |
| Beta-2 microglobulin, μg/mL, median (IQR) | 2.2 (1.8–3.2) | 2.6 (2.0–3.5) | 2.6 (1.9–4.0) | 0.2 |
| Hemoglobin, g/dL, median (IQR) | 13.7 (12.8–14.5) | 12.5 (11.2–13.6) | 12.4 (10.6–13.8) | 0.0004 |
| Creatinine, mg/dL, median (IQR) | 0.8 (0.7–1.0) | 1 (0.9–1.2) | 1.1 (0.9–1.3) | <0.0001 |
| Calcium, mg/dL, median (IQR) | 9.4 (9.1–9.6) | 9.4 (9.1–9.8) | 9.5 (9.1–9.8) | 0.6 |
| Mayo risk stratification for SMM, n | 23 | 248 | 552 | |
| Low, % | 39 | 43 | 90 | |
| Intermediate, % | 17 | 31 | 9 | |
| High, % | 44 | 26 | 1 | |
| Mayo risk stratification for SMM (sans BM), n | 23 | 248 | 552 | <0.0001 |
| M-spike ≤ 2 and FLC ≤ 20, % | 43 | 51 | 90 | |
| M-spike ≤ 2 or FLC ≤ 20, % | 43 | 36 | 9 | |
| M-spike > 2 and FLC > 20, % | 14 | 13 | 1 | |
| Mayo risk stratification for MGUS, n | 24 | 248 | 563 | <0.0001 |
| Low, % | 0 | 9 | 38 | |
| Low-intermediate % | 46 | 30 | 37 | |
| Intermediate % | 50 | 55 | 23 | |
| High % | 4 | 6 | 2 |
MGUS monoclonal gammopathy of undetermined significance, sFLC serum-free light chain, BMPCs bone marrow plasma cells, SMM smoldering multiple myeloma, IQR interquartile range, BM bone marrow, w/o without.