Estimate Thyroid Remnant and Metastasis by A Diagnostic Dose of 131I Scintigraphy Or 99 M T C Scintigraphy after A Therapeutic Dose of 131I.

Abstract

Background: Thyroid cancer is the only endocrine malignant tumor that is easily accessible to clinical examination, it also is the only endocrine gland where the malignant tumors affect all groups of age, both sexes, and spread by all possible routes local, lymphatic, and blood spread. Objectives:. To determine the accuracy of both imaging modalities in identifying persistent disease or distant metastases, to evaluate the impact of timing of  post a therapeutic dose of 131I on diagnostic yield.  Methods: We studied 83 cases and collected data from medical records, Tumor Therapy and Cancer Research Center at Shendi University (Sudan). This study was conducted between January 2016 and August 2021. Results: in this study, we noticed that most of the participants were females and constituted 275 (79.9%) of the study participants and the majority of participants were ages above 40 years (75.9%). Forty patients (48.2%) had positive family history. Thirty-three patients (39.8%) had similar conditions, thirty-two patients (38.6%) had chronic disease, and eighteen patients (21.7%) had Cancer. The clinical presentations were dominated by: neck swelling in 45 patients (54.2%). Forty-five patients (54.2%) had follicular carcinoma 35 patients (42.2%) had papillary carcinoma and 1 patient (1.2%) had mixed carcinoma. The most common site of Mets is bone (73.5%), lymph nodes (13.2%), lung Mets (8.3%), and another part (16.8%). In diagnostic WBS, it was found that most of the remnant was follicular (58.4%), followed by papillary 41.6% and no remnant in Hürthle or mixed carcinoma. The remnant is decreased with increasing the dose which disappears in patients who took more than 150 mci. Most remnants are present in patients in the age groups above 40 years (73.9%) and the remnant is found in females 77.9%. All of metastasis (100%) is follicular cell carcinoma. The metastasis is found only in patients above 40 years old, (51.8%) between (40-60) years, and (48.4%) more than 60 years. The most of metastasis was found in females 51.5%. All cases of metastasis seen in patients received less than 80 mci. Conclusion: Neck swelling is the most presenting symptom. The most common remnant was the follicular type found in females in age above 40 years remnant decreased with increased dose that disappeared in doses more than 150mci. All metastasis is follicular, and the commonest site of metastasis is bones (73.5%), with approximately the same occurrence in both genders and absent in patients who received higher doses. Conclusion: Both 131I scintigraphy and 99 mTc scintigraphy are effective in assessing thyroid remnants and metastases post- therapeutic 131I dose, but their entity may depend on patient-specific factors and clinical scenarios. While 131I scintigraphy remains the gold standard for metastatic detection, 99mTc scintigraphy offers a safer and faster alternative for evaluating thyroid remnants. We recommended the use of risk-base criteria to decide the appropriate diagnostic modality to individual patients. Consider 99mTc scinitigraphy for low-risk cases and 131I scintigraphy for high-risk patients.