Re-Mineralization of Large Pelvic Lytic Lesions By CT Imaging in Patients with Multiple Myeloma: The Arkansas Experience

INTRODUCTION

Profound osteolytic lesions are a hallmark of multiple myeloma (MM) bone disease. Bone destruction is associated with severely unbalanced bone remodeling, secondary to the secretion of osteoclast activating factors and significant osteoblast suppression. Lytic lesions of the pelvis are relatively common in MM patients and contribute to increase morbidity due to the high risk of fracture that frequently demands surgical intervention. Since we observed significant improvements in the pelvic CT of patients following total therapy 4 (TT4) we retrospectively analyzed the appearance on pelvic osteolytic lesions by CT during TT4 treatment for myeloma.

METHODS

The UAMS Myeloma data base was interrogated to identify patients enrolled on the TT4 trial. TT4 is a protocol designed for low risk MM patients as defined by a baseline plasma cell GEP score < than 0.66. The treatment protocol includes two induction chemotherapy cycles followed by tandem autologous bone marrow transplantation, two consolidation cycles and 3 years of maintenance. During treatment, patients were exposed to alkylating agents, IMIDS and proteasome inhibitor agents as well as bisphosphonates. Baseline pelvic osteolytic lesions with > 1 cm in minimal diameter identified by PET/CT or CT of the pelvis were compared to the most recent radiological study available for the same subject. All identified cases were reviewed by radiology faculty to confirm the baseline and follow-up reported findings. Radiological findings were correlated with disease status, molecular subgroup, PET scanning and MRI.

RESULTS

Sixty-three (63) patients, with a median age of 62 years, were identified for this analysis. Baseline patient characteristics are shown in Table 1. With a median follow up of 41 months, CT studies indicate that 44% (28/63) of patients with large baseline pelvic lytic lesions achieved re-accumulation of radio-dense mineralized tissue at the lytic site. Sixty-eight percent of such patients reached at least VGPR. The average size of the lytic lesions that re-mineralized was 4.0 cm (minimum 1.3 cm - maximum 10 cm). Baseline GEP-defined molecular subgroups and cytogenetic distribution was not different from the entire patient population of TT4.

CONCLUSION

This study clearly shows that mineral redeposition in large pelvic lytic lesions of MM patients on TT4 is achievable in a significant proportion of individuals. We observed that the amount of re-mineralization was prominent in pelvic lytic lesions with cortical bone destruction. Since flat bones, such as the pelvis, are formed via intramembranous ossification further investigation of the mechanism responsible for this effect is warranted at skeletal sites with different regenerative capacity. These data also suggest that, contrary to much dogma, MM bone lesions can regain matrix mineralization capacity.