Somatostatin receptor based theranostics for Non-NET tumors

Introduction: Somatostatin receptorm (SSR) based theranostics is now widely applied in neuroendocrine tumors. Both diagnostic arm 68Ga-dotatate and therapeutical arm 177Lu-Dotatate have received FDA approval.

Somatostatin receptor is commonly expressed in other types of tumor than neuroendocirine tumors such as menigioma, medullary thyroid cancer, nasopharyngeal cancinoma (NPC), angiosarcoma etc. It is scientifically reasonable to assume usefulness of somatostatin receptor based theranostics in those conditions. The potential benefits of this application could be enormous.

This presentation aims to educate professionals about this less well estabolished field by expliciting the scientific foundation, summarizing the current available literature and by displaying the outcome of our own experimental study cohort.

Methods: There have been scattered publications in investigational use of this theranostic aproach. Our center has years', limited but meaningful experience in applying this theranostic pair to meningoma, angiosarcoma and nasopharyngeal carcinoma. The clinical outcome is encouraging and inspirational.

Published literature will be summarized and our own unpublished case cohort are displayed to elucidate the usefulness, drawbacks, and further direction of somatostatin receptor based theranostics in non-NET tumors.

Results: 68Ga-dotatate scan for meningioma is highly sensitive and specific. In our center, it has become a routine modality to differentiate difficult brain space occupying lesions, e.g. metastasis vs meningioma. There are also cases of successful treatment with 177Lu-dotatate for recurrent, multifocal, symptomatic meningiomas. Illustrative images are displayed.

Significant percentage of NPC is SSR positive that implies the potential of SSR based theranostics. We have imaged successfully a cohort of 20 patients of refractory or recurrent NPC with 68Ga-dotatate PET scan with tissue histology correlation done in most patients. The results serve as guidance for potential 177Lu PRRT.

Splenic angiosarcoma is an invasive cancer with no limited systemic treatment available. For patients with metastatic disease and positive on 68Ga-dotatate PET scan, 177Lu-Dotatate is given for standard 4 cycles. Some patients achieved partial response or stable disease after treatment. Post 177Lu-Dotatate SPECT images show clearly radiopharmaceutical uptake in the lesions which matches diagnostic PET findings.

Conclusions: SSR is expressed in some types of non-NET tumors. This estabolish the scientific foundation of potential use of SSR based theranostics.

Currently this approach is still experimental, however our own preliminary results are ensouraging.

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