FLT3-ligand (FLT3-L) levels exceeding 92 pg/mL in bone marrow and 121 pg/mL in peripheral blood are associated with relapsed and refractory disease in patients with multiple myeloma, Normann Steiner, MD, and his colleagues report in a study published in PLoS ONE.
In the study of 14 patients with monoclonal gamm opathy of undetermined significance (MGUS), 42 patients with newly diagnosed myeloma, and 27 patients with relapsed/refractory myeloma, there was a 61% probability that patients with FLT3-L levels above 92 pg/mL in bone marrow had relapsed or refractory multiple myeloma and a 79% probability that those with FLT3-L levels of 92 pg/mL or less had not relapsed and were not refractory. Based on FLT3-L levels in peripheral blood, values of 121 pg/mL or more were associated with a 71% probability of relapsed or refractory disease. The likelihood of not having relapses or refractory disease was 87% for patients with values less than 121 pg/mL.
“FLT3-L could be useful as a marker to identify (relapsed or refractory multiple myeloma) patients and should be evaluated as a potential target for future therapy strategies,” Dr. Steiner of Innsbruck (Austria) Medical University, and his fellow researchers wrote in PLoS ONE.
The researchers obtained bone marrow aspirates from all patients. Peripheral blood was examined from 4 MGUS patients, 31 patients with newly diagnosed myeloma, and 16 patients with relapsed or refractory myeloma. Peripheral blood was also obtained from 16 control subjects.
The levels of four potential risk factors were measured – soluble TIE2, FLT3-L, endostatin, and osteoactivin. The most significant association with risk was seen with FLT3-L levels.
Expression of soluble TIE2 in bone marrow differed significantly among the three patient cohorts and may be driven by the same factors that influence FLT3-L levels. However, soluble TIE2 levels were not as effective at differentiating patients at risk for disease progression, the researchers wrote.
Soluble TIE2 expression in bone marrow was highest in MGUS patients (median 4003.97 pg/mL) in comparison to relapsed or refractory disease (median 2223.26 pg/mL; P = .03) and to newly diagnosed patients with myeloma (median 861.98 pg/mL; P less than .001). A statistically significant difference among bone marrow levels of soluble TIE2 was observed for newly diagnosed patients and those with relapsed or refractory disease (P = .03).
However, soluble TIE2 in peripheral blood plasma did not differ significantly in the three cohorts nor did it differ between patients and controls.
In contrast to TIE2 and FLT3-L, levels of endostatin were lowest (median 146.50 ng/mL) in bone marrow plasma samples of patients with relapsed or refractory disease. Levels were higher in MGUS patients (median 190.37 mg/dL) than in newly diagnosed myeloma patients (median 170.15 mg/mL; P = .5).
Similar to soluble TIE2, plasma levels of endostatin in peripheral blood did not differ significantly in the three patient cohorts. Measurements of endostatin in bone marrow and peripheral blood correlated significantly (P less than .001), and peripheral blood levels differed significantly (P less than .001) for patients and control persons.
Osteoactivin expression was highest in the MGUS cohort, with median bone marrow plasma levels of 36 ng/mL as compared with median levels of 24.92 ng/mL in newly diagnosed myeloma patients and 22.30 ng/mL in patients with relapsed or refractory myeloma. Osteoactivin levels in peripheral blood did not differ significantly in the three cohorts, but differed between patients and control subjects. Osteoactivin measures in bone marrow and peripheral blood correlated significantly.
Citation: Steiner N, et al. High levels of FLT3-ligand in bone marrow and peripheral blood of patients with advanced multiple myeloma. PLoS ONE 2017 Jul 20;12:e0181487. doi. org/10.1371/journal.pone.0181487.
On Twitter @maryjodales