Abstract
RationalePSMA-directed therapy for metastatic prostate cancer is gaining adoption as a treatment option. However, accumulation of 177Lu/225Ac-PSMA in the salivary glands remains a problem, with risk of dose-limiting xerostomia and potentially severe effect on the quality of life. Gustatory stimulation is an approach that has commonly been used in radioactive iodine therapy to reduce accumulation in the salivary glands. However, based on theoretical differences in biodistribution, it was hypothesized that this could potentially lead to adverse increased toxicity for PSMA-ligand therapy. The primary objective of this work was to determine if gustatory stimulation by eating an assortment of sweet/fatty/acidic foods during the biodistribution phase of [18F]DCFPyl could result in a clinically relevant (> 30%) change in the uptake of the tracer in the salivary glands.Methods10 patients who already received a whole-body [18F]DCFPyl PET/CT scan for evaluation of prostate cancer, underwent a repeat (intervention) PET/CT scan within a month of the first (control) scan. During the intervention scan, patients chose from an assortment of sweet/fatty/acidic foods, which they then chewed and swallowed for a period of time starting 1 min before tracer administration to 10 min thereafter. Data from both scans were analyzed by placing VOIs on the major salivary glands and segmenting them using relative thresholds.ResultsA slight increase in PSMA uptake in the parotid glands was observed on the intervention scan when compared to the baseline scan (+ 7.1% SULmean and + 9.2% SULmax, p < 0.05). No significant difference in PSMA uptake in the submandibular glands was seen.ConclusionsEating only slightly increases uptake of [18F]DCFPyl in the parotid glands. We nonetheless recommend refraining from gustatory stimulation during the administration and early biodistribution phase of radionuclide therapy with PSMA-ligands to reduce the risk of avoidable additional toxicity.
Highlights
Radioligand therapy (RLT) with prostate specific membrane antigen (PSMA) ligands has been gaining adoption as a treatment option for patients with metastatic prostate cancer
We recom‐ mend refraining from gustatory stimulation during the administration and early biodistribution phase of radionuclide therapy with PSMA-ligands to reduce the risk of avoidable additional toxicity
We examined the effect of gustatory stimulation by eating during the initial administration and biodistribution phase, on the uptake of [18F] DCFPyl in the salivary glands using intra-patient controlintervention Positron emission tomography (PET) scans
Summary
Radioligand therapy (RLT) with prostate specific membrane antigen (PSMA) ligands has been gaining adoption as a treatment option for patients with metastatic prostate cancer. A strategy that is frequently employed in radioactive iodine (131I) therapy for differentiated thyroid cancer to reduce salivary gland toxicity, is gustatory stimulation [9]. This stimulation leads to an increase in blood flow to the glands [12], and given their extensively perfused vasculature, this could result in an undesirable increase in the delivery of 131I to the glands. This is sometimes referred to as the ‘rebound effect’, and its impact is disputed [13]
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