Somatostatin receptor (SSTR) scintigraphy in patients with osteosarcoma

Effect of somatostatin analogue octreotide in medulloblastoma in xenograft and cell culture study

BACKGROUND

The effect and possible timing of nonradiolabeled somatostatin analogue octreotide are still not determined in the treatment of medulloblastoma, while the presence of somatostatin receptor type-2 (SSTR2) is proved in the majority of medulloblastoma by several authors.

PROCEDURES

Daoy, SSTR2A positive medulloblastoma cell culture was tested with octreotide in monotherapy and combined with cisplatin, etoposide, and vincristine. Daoy medulloblastoma mice xenograft was treated with octreotide alone.

RESULTS

In monolayer cell culture high-dose octreotide (44 microM) resulted in mitotic inhibition with parallel increment of apoptosis. Combination with cytostatic drugs did not result in additive or synergistic effect, but vincristine was partially antagonized. In medulloblastoma xenograft, octreotide monotherapy (100 microg/kg/day for 10 days) resulted in partial tumor growth inhibition.

CONCLUSIONS

High concentration of nonradiolabeled octreotide may have role in the treatment of medulloblastoma by long-term administration. Concomitant administration of octreotide with widely used cytostatic drugs against medulloblastoma will not have beneficial impact.

Detection of somatostatin receptors in human osteosarcoma

Background

The location of osteosarcoma in the metaphysis as well as the age of the patients during the most rapid tumour growth suggest that factors related to skeletal growth are involved in the pathogenesis of this tumour. In this aspect this study aims to detect somatostatin receptors in human osteosarcomas and correlate this finding with the clinical outcome of the tumour.

Patients and methods

Immunohistochemical staining for the presence of somatostatin receptors as well as overall survival and disease free survival rates were retrospectively studied in twenty-nine osteosarcoma patients.

Results

Four osteosarcomas with several aggressive biologic behaviour expressed somatostatin receptors. In these four young patients the event free rate was 0% and the overall survival rate was 50% at 4, 3 years. In contrast the event free survival rate of the twenty-five patients with negative somatostatin receptor status was 72% with an overall survival rate of 76% at 4,3 years.

Conclusion

The present study demonstrates the existence of somatostatin receptors in human osteosarcoma. Tumours expressing somatostatin receptors seemed to be aggressive with a very low disease free and overall survival rate compared to osteosarcoma with negative receptor status.

Functional imaging techniques for evaluation of sarcomas

Sarcomas are often characterised by significant histopathologic heterogeneity, both between and within tumours. This heterogeneity reflects physiologic, biochemical and genetic processes that are amenable to characterisation by functional imaging. Although anatomically based imaging modalities such as plain radiography, X-ray computed tomography (CT) and magnetic resonance imaging (MRI) remain the primary diagnostic modalities for staging sarcomas, nuclear medicine approaches including gamma camera scintigraphy and positron emission tomography (PET) are being used increasingly to provide complementary information in specific clinical situations. These include biopsy guidance within anatomically complex masses, staging, therapeutic response assessment and evaluation of residual mass lesions after treatment. This review aims to address the range of nuclear medicine techniques available for evaluation of bone and soft tissue sarcomas. A subsequent review discusses the clinical application of these techniques with a particular focus on PET.

Receptor-Mediated Tumor Targeting with Radiopeptides. Part 1. General Concepts and Methods: Applications to Somatostatin Receptor-Expressing Tumors

Radiolabeled peptides have become important tools in nuclear oncology, both as diagnostics and more recently also as therapeutics. They represent a distinct sector of the molecular targeting approach, which in many areas of therapy will implement the old "magic bullet" concept by specifically directing the therapeutic agent to the site of action. In this three-part review, we present a comprehensive overview of the literature on receptor-mediated tumor targeting with the different radiopeptides currently studied. Part I summarizes the general concepts and methods of targeting, the selection of radioisotopes, chelators, and the criteria of peptide ligand development. Then, the >400 studies on the application to somatostatin/somatostatin-release inhibiting factor receptor-mediated tumor localization and treatment will be reviewed, demonstrating that peptide radiopharmaceuticals have gained an important position in clinical medicine.