Salivary gland toxicity after PSMA-targeting radioligand therapy (PRLT) in patients with advanced prostate cancer : a single-center systematic investigation

  • Introduction: PSMA radio ligand therapy (PRLT) is a promising treatment for mCRPC patients. However, an intense uptake to the salivary glands (SG) can be observed with moderate xerostomia. For Ac-225- PSMA xerostomia became even dose-limiting. Objective of this study was a systematic investigation of SG dysfunction after PRLT using patient-based and clinical data as well as salivary gland scintigraphy (SGS) and PSMA-PET/CT parameters.
  • Methods: 3 patient groups undergoing Lu-177 PSMA or a combination of Ac-225 and Lu-177 PSMA (Tandem-PRLT) were studied. Group I consisted of 91 patients receiving 2 cycles of Lu-177 PSMA. Clinical examination, a standardized questionnaire (sXI), SGS and SUVmax and the metabolic volume of the SGs on PSMA-PET/CT were assessed at baseline and follow-up. Group II with 40 patients, that underwent 2-9 cycles of PRLT (up to 61.8 GBq) was investigated by the same protocol. In group III, 18 patients after 1 cycle of Tandem-PRLT were investigated similarly.
  • Results: In group I, 24 % of the patients had xerostomia grade 1, in group II xerostomia grade 1-2 occurred in 40 %. sXI scores rose significantly with a correlation between the follow-up sXI score and mouth dryness. SGS showed no significant changes. While no changes of the SUVmax of the SGs were found, a significant decline of the metabolic volume both in short and long-term follow-up was found. Age, previous treatments, tumor burden or cumulative activity showed no influence on SG toxicity. In group III 12/18 patients reported xerostomia grade 1-2, sXI rose from 9.5–14.0, a reduction of the EF on the SGS and a decrease of the MV on PSMA PET/CT was found.
  • Conclusion: Only mild SG toxicity after Lu-177 PSMA was observed with minor clinical relevance (compared to EBRT or radioiodine therapy). However, after one cycle of Tandem-PRLT a significant SG dysfunction was observed. This protocol can objectify SG toxicity of PRLT in future studies. Preventive strategies remain an urgent clinical need.


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