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Rationale PSMA-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. Methods 10 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. Results A 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 Conclusions Eating 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.

Purpose To test if the relative change in FDG-PET SUVmax over the course of treatment was associated with disease progression and overall survival. Additionally, the prognostic values of other first-order PET-metric changes were investigated. Methods The study included 38 patients with stage II–III NSCLC, who underwent concurrent chemoradiotherapy. Patients received two pre-treatment FDG-PET scans and four during-treatment scans at weekly intervals. SUVmax was normalized to the start of treatment and analyzed using linear regression. Linear regression coefficients of other first order PET-metrics were grouped according to dissimilarity. Associations to patient outcome were analyzed using Cox hazard ratio. Results Twenty-eight patients satisfied the criteria for analysis. All PET-metrics demonstrated a strong linear correlation with time during treatment [median R-range: −0.87: −0.97]. No strong associations (p > 0.10) were found for the relative slope of SUVmax to patient outcomes. Other first-order metrics did correlate with outcome but the single imaging time-point maximizing the association of PET response with outcome varied per PET metric and outcome parameter. Conclusion All investigated FDG PET metrics linearly decreased during treatment. Relative change in SUVmax was not associated to patient outcome while several other first order PET-metrics were related to patient outcome. A single optimal imaging time-point could not be identified.

Radiation therapy is an effective treatment modality for a variety of cancers. Despite several advances in delivery techniques, its main drawback remains the deposition of dose in normal tissues which can result in toxicity. Common practices of evaluating toxicity, using questionnaires and grading systems, provide little underlying information beyond subjective scores, and this can limit further optimization of treatment strategies. Nuclear medicine imaging techniques can be utilised to directly measure regional baseline function and function loss from internal/external radiation therapy within normal tissues in an in vivo setting with high spatial resolution. This can be correlated with dose delivered by radiotherapy techniques to establish objective dose-effect relationships, and can also be used in the treatment planning step to spare normal tissues more efficiently. Toxicity in radionuclide therapy typically occurs due to undesired off-target uptake in normal tissues. Molecular imaging using diagnostic analogues of therapeutic radionuclides can be used to test various interventional protective strategies that can potentially reduce this normal tissue uptake without compromising tumour uptake. We provide an overview of the existing literature on these applications of nuclear medicine imaging in diverse normal tissue types utilising various tracers, and discuss its future potential.

Rationale Salivary glands are highly perfused and express the prostate-specific membrane antigen (PSMA) receptor as well as the sodium—iodide symporter. As a consequence, treatment with 177Lu/225Ac-PSMA for prostate cancer or 131I for thyroid cancer leads to a high radiation dose in the salivary glands, and patients can be confronted with persistent xerostomia and reduced quality of life. Salivation can be inhibited using an antimuscarinic pharmaceutical, such as glycopyrronium bromide (GPB), which may also reduce perfusion. The primary objective of this work was to determine if inhibition with GPB could provide a considerable (> 30%) reduction in the accumulation of administered 123I or 68Ga-PSMA-11 in salivary glands. Methods Ten patients who already received a whole-body 68Ga-PSMA-11 PET/CT scan for (re)staging of prostate cancer underwent a repeat PET/CT scan with tracer administration at 90 min after intravenous injection of 0.2 mg GPB. Four patients in follow-up after thyroid cancer, who had been treated with one round of ablative 131I therapy with curative intent and had no signs of recurrence, received 123I planar scintigraphy at 4 h after tracer administration without GPB and a repeated scan at least one week later, with tracer administration at 30 min after intramuscular injection of 0.4 mg GPB. Tracer uptake in the salivary glands was quantified on PET and scintigraphy, respectively, and values with and without GPB were compared. Results No significant difference in PSMA uptake in the salivary glands was seen without or with GPB (Mean SULmean parotid glands control 5.57, intervention 5.72, p = 0.50. Mean SULmean submandibular glands control 6.25, intervention 5.89, p = 0.12). Three out of 4 patients showed increased 123I uptake in the salivary glands after GPB (Mean counts per pixel control 8.60, intervention 11.46). Conclusion Muscarinic inhibition of salivation with GPB did not significantly reduce the uptake of PSMA-ligands or radioiodine in salivary glands, and can be dismissed as a potential strategy to reduce toxicity from radionuclide therapies.

OBJECTIVE The purpose of this study was to prospectively investigate the value of a standardized 18F-fluorodeoxyglucose (18F-FDG)-PET/computed tomography (CT) protocol for imaging of primary bladder cancer, using standardized bladder flushing and filling. METHODS We included 19 patients with cT1-4 bladder cancer. A Foley catheter was inserted before 18F-FDG injection. PET/CT imaging was performed according to four bladder protocols: (1) bladder empty; (2) bladder empty after flushing; (3) bladder filled with 50 ml saline; and (4) bladder filled with 100 ml saline. Tumour visibility was assessed and compared with histopathology or CT and cystoscopy. RESULTS The procedure was successfully completed in 16 out of 19 patients. The reference standard revealed a bladder tumour in 16 out of 19 patients. Sensitivity of protocols 1 and 2 was 0.38 [95% confidence interval (CI), 0.16-0.64] compared with 0.63 (95% CI, 0.36-0.84) for protocols 3 and 4. CONCLUSION Flushing and subsequent retrograde filling of the bladder results in the highest rate of tumour visualization and quantification. Flushing alone is inferior.