TY - JOUR T1 - <strong>Injection of botulinum toxin for preventing salivary gland toxicity after PSMA-Radio-Ligand-Therapy - an empiric proof of a promising concept</strong> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 525 LP - 525 VL - 59 IS - supplement 1 AU - Thomas Langbein AU - Richard Baum AU - AVIRAL SINGH AU - Christiane Schuchardt AU - Fabian Volk AU - Harshad Kulkarni Y1 - 2018/05/01 UR - http://jnm.snmjournals.org/content/59/supplement_1/525.abstract N2 - 525Objectives: The potential dose-limiting toxicity - especially when using alpha-emitters like Ac-225- or Bi-213, remains an unresolved issue in PSMA radioligand therapy (PRLT) of metastatic castration-resistant prostate cancer (mCRPC) due to the normal biodistribution of PSMA-radioligands in the salivary as well as in the lacrimal glands. Experience from over decades in external beam radiotherapy (EBRT) of the head and neck region demonstrates that severe xerostomia could become a life-quality-limiting factor. Since recent studies suggest a more PSMA-independent uptake in the salivary and lacrimal glands (1), suppressing the gland metabolism appears to be a promising method to achieve a lower uptake. Because of its safety and feasibility, injection of botulinum toxin into the salivary glands is commonly used to treat severe sialorrhoea (even in children) and has already been investigated as a potential radioprotective agent in EBRT (2). Methods A 63-year-old patient with mCRPC received multifocal ultrasound-guided injections of botulinum toxin A, totally 80 units, into his right parotid gland after a detailed informed consent. A dynamic salivary gland scintigraphy (SGS) using Tc-99m pertechnetate was performed before and after 70 h. At 45 days p.i., SGS as well as Ga-68-PSMA-PET/CT were performed. Standardized uptake values (SUV) of the right and left parotid glands were compared to the baseline PET/CT study. The patient underwent regular clinical follow up. Results Ga-68-PSMA-PET/CT performed 45 days after the botulinum toxin injection showed a heterogeneous, but highly significant reduction of the radioligand uptake by up to 60 % (SUVmean) in the injected right-sided parotid gland as compared to the left one. There was a drop of the SUVmean in the right parotid gland by up to 64 %, whereas no significant change in uptake of the left parotid gland was noted, when compared to the baseline PET/CT. The SGS also revealed a distinct decline in the peak uptake of Tc-99m pertechnetate in the injected parotid gland. The patient didn’t report any adverse effects of the injections throughout the follow-up period of now up to 4 months. Conclusion Intraparenchymal botulinum toxin injection impressively decreases the uptake of PSMA radioligands in the salivary glands. Therefore this approach could be a significant breakthrough for salivary gland protection under PSMA radioligand therapy. ER -