Influence Of Radioiodine Therapy To The Major Salivary Gland For Differentiated Thyroid Cancer

BackgroundThe incidence of thyroid cancer is increasing,and this disease is projected to become the fourth most common type of cancer worldwide.Differentiated thyroid cancer(DTC)is the most common subtype of thyroid cancer.Radioactive iodine therapy(RAIT)is an established treatment for DTC,with infrequent serious adverse effects;among the reported serious adverse effects,sialadenitis symptoms have been relatively commonly described,which can affect quality of life for long term.Salivary gland scintigraphy(SGS)is the first choice and reliable method for salivary gland follow-up after RAIT because of its high sensitivity to functional alterations.But which is not suitable for repeated examinations due to radiation.In contrast,ultrasound with non-invasive and poor sensitivity,but it can dynamically observe the pathological process.Although ultrasound is the first choice for evaluating major salivary gland diseases,few foreign researchers have studied the ultrasound changes of salivary glands in patients with DTC after RAIT,which are limited to cross-sectional observation due to the irregular frequency and interval of follow-up.And there is no comparative study between ultrasound and salivary gland scintigraphy or other means.ObjectiveThis study aimed to determine the prevalence of radioiodine-induced salivary gland damage by evaluating progressive changes in salivary glands on ultrasound images and the outcomes of these progressive changes to identify risk factors and provide a basis for clinical intervention;to evaluate the relation between ultrasound changes of salivary glands and long-term dry mouth;and to explore whether ultrasound can be used as a long-term dynamic follow-up method and complementary to SGS here by contrast between SGS and the main salivary gland ultrasound.MethodsIn total,498(140 males,358 females,age:39.33±13.39 y)DTC patients who underwent total or near-total thyroidectomy and postoperative RAIT were retrospectively reviewed;446 patients completed five or more follow-up visits with ultrasound(approximately 36 months afer last RAIT).The influencing factors of ultrasound positivity were analyzed by generalized estimating equations;the correlation of main salivary gland ultrasound features and long-term dry mouth were analyzed by conventional statistical methods.The functional indexes of SGS one year after RAIT were compared with the ultrasound features of the same period.The functional indexes were compared among 3 SGSs(before RAIT,3/6months after RAIT and one year after RAIT,respectively).ResultsPart1 The 446 patients had 161 positive results.ultrasound showed a coarse echotexure,decreased echogenicity,a lobulated margin and a decreased gland size.The difference in the extent of the change was statistically significant(all P<0.01).Of the 161 positive cases with 644 glands,34.5%of the parotid glands were involved,and 4.5%of the submandibular glands were involved;among these,0.4%of the parotid glands and 75.0%of the submandibular glands eventually achieved negative ultrasound results.Part2 The frequency of ultrasound salivary gland changes increased with increasing follow-up duration(P<0.001),and then possibly stabilized at about 33%.The frequency of salivary gland changes was higher in females than in males(P<0.001),and in the cumulative dose>310 mCi group than in other groups(P<0.001).Part3 Age and first dose was related to the difference in dry mouth(P<0.001).The positive rate for the last salivary gland ultrasound was related to the difference in dry mouth(P=0.024).Part4 The ejection fraction of parotid before RAIT and uptake index of parotid for one year after RAIT on salivary gland scintigraphy,was correlated with the positive rate of ultrasound changes.The total function scores of each gland and the sub-functional scores of most glands were correlated with ultrasound feature scores,which were statistically significant(all P<0.05).ConclusionSialadenitis is common in DTC patients after RAIT.The number of follow-up ultrasound examinations was positively correlated with the frequency of post-RAIT change,and possibly stabilized at approximately 3 years.Most changes were not resolve,suggesting that its recent changes may predict long-term damage.A cumulative dose was an important factor in salivary gland damage.The correlation between the ultrasound feature score and the SGS function score verified the validity of the ultrasound assessment.Therefore,the dose of 131I should be strictly controlled in clinical practice to the reduction of side effects when ensuring the efficacy.