FLT-PET in Haematological Disorders: A Novel Technique To Analyze the Proliferative Activity of the Bone Marrow Compartment.

Few diagnostic procedures are available to determine the degree of bone marrow cellularity and the numbers of cycling cells in patients with hematopoietic disorders. Therefore non-invasive imaging of the bone marrow compartment may be helpful. Recently the PET tracer [18F]-3′-fluoro-3′-deoxy-L-thymidine (FLT) has been developed. FLT uptake is related to the DNA synthesis rate and increases with higher proliferation rates and may therefore visualise the high cycling activity of haematopoietic cells in the bone marrow compartment. In the present study the feasibility of visualisation and quantification of the bone marrow compartment activity with FLT-PET was used to distinguish different haematological disorders.

Clinical and laboratory data of 18 patients with low-risk myelodysplasia (MDS), chronic myeloproliferative disorders, myelofibrosis, aplastic anemia or multiple myeloma were correlated with the results of FLT-PET imaging using visual analysis and SUV. Findings were compared with those in normal controls (n=14).

With SUV analysis of the femura, thoracic and lumbar vertebral body in conjunction with visual analysis a distinction could be made between MDS (n=9), chronic myeloproliferative disorders (n=3) and myelofibrosis (n=3) compared to normal controls (p<0.001). A significant increase in FLT uptake in the defined areas was observed in all the studied patients with MDS and myeloproliferative disorders. In addition a significant expansion of the bone marrow compartment was shown (p<0.001). No correlation was found between Ki-67 staining of bone marrow biopsies and FLT uptake. In contrast, patients with myelofibrosis demonstrated a decline in bone marrow FLT uptake compared to normal controls but a significant increase in liver and spleen uptake. Osteolytic lesions of multiple myeloma patients and patients with aplastic anemia showed a strong reduction in bone marrow FLT uptake.

The results indicate that FLT-PET can be used to visualize the proliferative activity of the bone marrow compartment and may be helpful to distinguish separate haematological disorders.