Zoledronic Acid Increases Bone Mineral Density in Patients with Thalassemia Intermedia-Induced Osteoporosis Regardless of the Incessant Bone Marrow Expansion.

Osteoporosis represents an important cause of morbidity in adult patients with thalassemia. Its pathogenesis is multifactorial, and includes mainly bone marrow expansion, endocrine dysfunction and iron overload. Patients with thalassaemia intermedia (TI) seem to have a more expanded bone marrow with pressure on cortical bone, which causes pain and bone loss in several cases. The measurement of soluble transferrin receptor (sTfR) and erythropoietin (Epo) in the serum is considered as accurate marker of erythropoietic activity in thalassemia. Bisphosphonates are potent inhibitors of osteoclast activity and have been used for the management of thalassemia-induced osteoporosis. The aim of this study was to evaluate the effect of zoledronic acid, the most potent aminobisphosphonate, on bone mineral density (BMD) of patients with TI and explore possible correlations with bone marrow expansion and erythropoietic activity. Thirty-five patients with TI and osteopenia or osteoporosis (13M/22F, median age 45 years) were evaluated. Twenty-three were randomized to receive zoledronic acid, 4 mg, IV, every 3 months (n=12) or every 6 months (n=11) for one year, while 12 patients received placebo every 3 months. There was no difference in terms of the presence of gonadal dysfunction between the three studied groups. BMD of the lumbar spine (L), femoral neck and forearm was determined in all patients, using DEXA, before and 12 months after treatment. Bone marrow expansion was assessed by the measurement of sTfR and Epo serum levels, using an ELISA methodology (R&D Systems, Minneapolis, MN, USA), before and 12 months post zoledronic acid or placebo administration. In all patients markers of bone remodelling, such as C-telopeptide of collagen type-I (CTX) and bone specific alkaline phosphatase (bALP) were also measured by ELISA (Nordic Bioscience Diagnostics, Herlev, Denmark, and Quidel, San Diego, CA, USA, respectively). Patients were asked to quantify their degree of bone pain on Huskisson’s visual analogue scale and the McGill-Melzack scoring system before and 12 months post-therapy. All patients had increased values of sTfR, Epo, CTX, and bALP compared with 40 controls of similar age and gender (p<0.001). Patients who received zoledronic acid showed a significant increase in their L-BMD (p=0.01), which was accompanied by a dramatic reduction in CTX and bALP values ((p<0.001). There was no difference in terms of L-BMD changes between zoledronic acid groups. Placebo group showed an aggravation of L-BMD (p=0.041) and markers of bone remodelling at 12 months. No other changes were observed in the BMD of other sites. Zoledronic acid reduced bone pain, which remained stable in placebo group during the study period. There was only weak correlation between baseline sTfR levels and L-BMD, while there was no correlation between Epo or hemolytic parameters (indirect bilirubin, reticulocytes counts, and LDH) with BMD of all studied sites. Serum sTfR and Epo values showed a significant elevation after 12 months of therapy in all studied groups (p<0.01, p<0.02, and p<0.01, respectively); this elevation was irrespective of the L-BMD changes. This study suggests that the increase of BMD produced by zoledronic acid in TI is irrespective of the continuous increase of bone marrow expansion, which is considered a major cause of bone loss in this hemoglobinopathy.