Scintigraphy with 99mTc-pertechnetate in the diagnosis of radiation lesions of the salivary glands after treatment of papillary carcinoma of the thyroid gland

Abstract

Relevance. The issue of diagnosing and treating of radiation lesions in the salivary glands remains relevant due to the widespread use of radioiodine therapy for highly differentiated thyroid cancer. Sialoscintigraphy with 99mTc-pertechnetate is the most informative method for assessing salivary gland function. There have been few articles on the use of sialoscintigraphy, and it is yet debatable how the clinical, morphological, and functional characteristics of salivary glands exposed to radioiodine therapy relate to one another. The aim of the research was to study the extent and nature of functional disorders of the major salivary glands that occurred in patients after radioiodine therapy for thyroid carcinoma by using sialoscintigraphy with the radiopharmaceutical 99mTc-pertechnetate, as well as the factors affecting the severity of the related disorders. Materials and Methods. Dynamic sialoscintigraphy with 99mTc-pertechnetate [99mTcO4 – ] was used to study the salivary gland function in 30 patients with papillary thyroid carcinoma who developed chronic radiation sialadenitis after total thyroidectomy and radioactive iodine therapy. The findings of the investigations were compared to clinical data. Results and Discussion. Based on sialoscintigraphiic data, substantial abnormalities of the secretory, excretory, and concentration functions of the major salivary glands were found in patients with clinical signs of chronic radiation sialadenitis. The impairments had considerable individual and topographic variability. In most cases, the salivary glands were affected unevenly: against the background of a decrease in or total loss of function of one or more of them, compensatory changes occurred in other glands. Decompensation signs, as evidenced by diminished secretion and concentration capacity, were greater with the decreased excretion ratio (50.0±4.6% of patients) than with the reduced secretory activity ratio (30.0±4.2%) or the concentration ratio (20.8±3.7% of patients). The excretory function of the salivary glands was most negatively impacted; the median value of the excretion ratio was 0.690 (0–0.855 as opposed to the normal range of 0.99–1.02). The median value of the secretion ratio decreased to 1.015 (0.630–1.2 versus the normal range of 1.21–1.26). The nature and severity of the change in sialoscintigraphy indices were not affected by the underlying illness stage or the 131I dose used. Conclusions. Radiation sialoadenitis developing in thyroid cancer patients who undergo thyroidectomy and radioiodine therapy causes persistent functional impairments with significant clinical manifestations. Dynamic sialoscintigraphy with 99mTc-pertechnetate allows objectifying the nature of these functional abnormalities, selecting the optimal therapeutic program, and evaluating the effective of treatment.