The use of local injection of 153Samarium-EDTMP in conjunction with kyphoplasty for palliation bone metastasis

Abstract

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Objectives: 1.We attempted intravertebral injection of 153Samarium-EDTMP (153Sm) with kyphoplasty for palliative treatment of vertebral metastases to strengthen the vertebra along with extinguishing metastatic vertebral lesion with least myelosupression. Thus adding cancericidal effect to the benefit of kyphoplasty. 2.Measure local and systemic radiotracer distribution after intravertebral injection of 153Sm-EDTMP. 3.Observe treatment response and measure changing in bone mineral density.

Methods: IRB approval for an off label use of 153Sm was obtained. Six patients with documented vertebral bone metastasis were studied (Thoracic in 1 and lumbar spine in 5). Primary cancer was lung (2), prostate (1), maxillary sinus (1), myeloma (1) and colon (1). All patients had Bone and MRI scans prior to procedure. Bone density scan was contemplated in all. Kyphoplasty procedure was carried out in the operating room using the known protocol of polymethylmethacrylate bone cement administration with 1-2 mCi of 153Sm was added. After procedure, a first whole body Samarium scan was obtained before micturition (<2 hours after procedure), followed by whole body Samarium scans in all but one, 24, 48, and 72 hours. Long-term follow up bone scans and MRI scans were obtained every 2-3 months.

Results: The first scan (<2 hours) demonstrated radiotracer concentration in the injected lesion in all. The percentage of tracer activity in the vertebra as related to whole body was 73%, and 76% (one case failed to measure, 3 cases failed planned injection). There was evidence of systemic absorption with absorption rates of 24% and 27%. The absorbed radiotracer also targeted other skeletal metastatic lesions (ribs, other vertebrae and pelvic bone). 1 of 6 cases had follow up bone scans in 2 months and 4 months showed decreasing intensity of radiotracer uptake in the lesion of injected site (T10) as well as in a lesion away from injected site (right posterior ninth rib). The measured maximal counts per pixel in T10 was 774 (before), 205 (2 months after), and 168 (4months after). The measured maximal counts per pixel in right posterior ninth rib was 582 (before), 197(2 months after), and 193 (4 months after). There was consistent dramatic improvement of pain score in all patients. Significant myelosupression did not occur in any.

Conclusions: Local 153Sm injection in conjunction with kyphoplasty technique may add important treatment choice in patients with painful vertebral metastases with a potential for less myelosupression. Concentration of 153Sm at site of injection seemed to outstripped reported uptake after systemic injection.