Injection of Botulinum Toxin for Preventing Salivary Gland Toxicity after PSMA Radioligand Therapy: an Empirical Proof of a Promising Concept

The dose-limiting salivary gland toxicity of ²²⁵Ac-labelled PSMA for treatment of metastatic, castration-resistant prostate cancer remains unresolved. Suppressing the metabolism of the gland by intraparenchymal injections of botulinum toxin appears to be a promising method to reduce off-target uptake. A ⁶⁸Ga-PSMA PET/CT scan performed 45 days after injection of 80 units of botulinum toxin A into the right parotid gland in a 63-year-old patient showed a decrease in the SUVmean in the right parotid gland of up to 64% as compared with baseline. This approach could be a significant breakthrough for radioprotection of the salivary glands during PSMA radioligand therapy.