Evaluation of Parotid Salivary Gland Echo Texture by Ultrasound Examinations and Correlation With Whole-Body Scintigraphy After Radioiodine Therapy in Patients With Differentiated Thyroid Carcinoma

Ultrasound and Sialendoscopy Findings in Radioactive Iodine-Induced Sialadenitis: Comparative Analysis and Possible Impact on Management

BACKGROUND

To assess the correlation/association between ultrasound and sialendoscopy findings in radioactive iodine therapy-induced sialadenitis (RAIS).

METHODS

Patients presenting with RAIS were investigated with ultrasound and sialendoscopy. Four pathologic ultrasound parameters and seven pathologic sialendoscopy parameters were retrospectively assessed. Correlations/associations between ultrasound and sialendoscopy findings and associations between the changes between the first and last ultrasound and sialendoscopy findings were assessed separately for the parotid (PG) and submandibular glands (SMG).

RESULTS

Sixty-seven patients were included. In the first examination, 107 glands were investigated (PGs 88.8%, SMGs 11.21%), and in the last examination, 64 glands were investigated (90.6% PGs, 9.4% SMGs). Highly significant positive associations were observed between the severity or category of ultrasound and sialendoscopy findings for first and last examinations for PGs (both p = 0.0001) and SMGs (p = 0.002; p = 0.037). Duct dilation had a significant negative association with the sialendoscopy findings for PGs in the first and last examinations (both p = 0.0001), but not for SMGs. Comparison of changes in the ultrasound and sialendoscopy findings between the first and last examinations showed a significant positive association for PGs (p = 0.0001) but not for SMGs.

CONCLUSIONS

Ultrasound and sialendoscopy findings for the parenchyma and duct system in RAIS showed significant associations/correlations and can be useful for effective management in RAIS.

Ultrasound Changes in Salivary Glands after Radioactive Iodine Treatment in Benign Diseases and Differentiated Cancer of Thyroid Glands in Consideration of Dose and Time Dependency

PURPOSE

To assess ultrasound (US) features observed in salivary glands after radioactive iodine treatment (RAIT) in relation to the dose and time interval after RAIT.

MATERIALS AND METHODS

A retrospective analysis of US findings regarding the salivary glands of patients presenting after RAIT due to thyroid cancer (Group 1, n=99) or benign thyroid diseases (Group 2, n=25). The control group consisted of randomly selected patients (no RAIT, Group 3, n=100). Groups were compared regarding RAIT dose, symptoms, and US findings (duct dilation, hypoechoic/heterogeneous parenchyma, parenchymal loss). The association of the presence of US parameters after RAIT with various dose levels (2000-15000MBq) and time intervals (24, 60, 120 months) and the differences between the groups was evaluated.

RESULTS

Significant differences between US parameters were noted when comparing Group 1 with Group 2 or 3. Nothing of relevant significance was noted when Groups 2 and 3 were compared. US features indicating a slight or moderate sialadenitis showed the most significant associations with doses <4000MBq and time intervals <24 months after RAIT. US changes indicating a serious sialadenitis or even gland atrophy showed the most significant association at doses between >7000-9000MBq and when US was performed >60 months after RAIT.

CONCLUSION

Our results point to a dose and time dependency of pathologic US findings in RAIT-induced effects on the major salivary glands. Based on the US findings, a better estimation of the current impact of RAIT on the salivary glands and the further prognosis appears possible.

Is there a role for diagnostic scans in the management of intermediate-risk thyroid cancer?

Radioiodine (RAI) is selectively recommended for intermediate-risk differentiated thyroid carcinomas (DTC). The information gleaned from pretherapy stimulated thyroglobulin levels (sTg) and diagnostic 131I whole-body scans (DxWBS) to guide therapy remains controversial. The present study aimed at evaluating the impact of preablation sTg and DxWBS in the management of intermediate-risk DTC. A retrospective analysis of 301 intermediate-risk DTC patients submitted to total thyroidectomy and RAI therapy was performed. Pretherapy sTg and DxWBS and post-therapy WBS (RxWBS) findings were analyzed and compared to outcomes. Fifty-two patients (17.3%) had metastases diagnosed by DxWBS and/or RxWBS. The DxWBS identified 10.6% of patients with functioning metastases, including unexpected distant metastases. If combined with SPECT-CT, DxWBS detected RAI-avid metastases more frequently, particularly lymph node metastases (13.1% vs 4.2% planar WBS, P = 0.015). The DxWBS findings modified patient management in 8.3%. A pretherapy sTg <1 ng/mL was associated with a low false-negative rate for the presence of metastases (5.2%), and its performance in excluding metastasis was improved by a negative DxWBS (2.7% of patients with both negative exams had metastases in RxWBS). A sTg <1 ng/mL predicted statistically significant lower rates of recurrent/persistent disease and biochemical/structural incomplete responses. In conclusion, preablation sTg and DxWBS contribute to the detection of unknown or persistent metastatic disease in intermediate-risk DTC patients. A sTg <1 ng/mL in combination with a negative DxWBS is highly suggestive of the absence of remaining malignant disease, and one may consider deferring RAI ablation if both exams are negative. A stunning effect is rarely observed and it does not impair proper treatment of metastases.

Assessment of salivary gland function after 177Lu-PSMA radioligand therapy: Current concepts in imaging and management

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The United States food and drug administration has recently granted approval to the targeted ¹⁷⁷Lu-PSMA-617 therapy in prostate cancer patients.

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Salivary glands show high PSMA-ligand uptake and are prone to radiation damage secondary to accumulation of ¹⁷⁷Lu-PSMA-617.

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Salivary gland scintigraphy is a noninvasive highly reproducible technique, useful for objective and quantitative assessment of salivary flow and function of parotid and submandibular glands and can help detect early changes post ¹⁷⁷Lu-PSMA-617 therapy.

Prostate specific membrane antigen (PSMA) is a transmembrane protein that is highly expressed on prostate epithelial cells and is strongly upregulated in prostate cancer. Radioligand therapy using beta-emitting Lutetium-177 (¹⁷⁷Lu)-labeled-PSMA-617, a radiolabeled small molecule, has gained attention as a novel targeted therapy for metastatic prostate cancer, given its high affinity and long tumor retention, and rapid blood pool clearance. In March 2022, the United States Food and Drug administration has granted approval to the targeted ¹⁷⁷Lu-PSMA-617 therapy for treatment of patients with PSMA-positive metastatic castration resistant prostate cancer, who have been previously treated with an androgen-receptor pathway inhibitor and taxane-based chemotherapy. Studies have demonstrated the adverse effects of this treatment, mainly encountered due to radiation exposure to non-target tissues. Salivary glands show high PSMA-ligand uptake and receive increased radiation dose secondary to accumulation of ¹⁷⁷Lu-PSMA-617. This predisposes the glands to radiation-mediated toxicity. The exact mechanism, scope and severity of radiation-mediated salivary gland toxicity are not well understood, however, the strategies for its prevention and treatment are under evaluation. This review will focus on the current knowledge about salivary gland impairment post ¹⁷⁷Lu labeled PSMA-based radioligand therapies, diagnostic methodologies, and imaging with emphasis on salivary gland scintigraphy. The preventive strategies and known treatment options would also be briefly highlighted.