Radioactive Iodine Therapy in Patients with Differentiated Thyroid Cancer: Study of External Dose Rate Attenuation Law and Individualized Patient Management

Integrating US-guided FNAB, BRAFV600E mutation, and clinicopathologic characteristics to predict cervical central lymph-node metastasis in preoperative patients with cN0 papillary thyroid carcinoma

BACKGROUND

The prevalence of cervical central lymph-node metastasis (CLNM) is high in patients with papillary thyroid carcinoma (PTC). There is considerable controversy surrounding the benefits of prophylactic central lymph-node dissection (pCLND) in patients with clinically negative central compartment lymph nodes (cN0). Therefore, it is crucial to accurately predict the likelihood of cervical CLNM before surgery to make informed surgical decisions.

METHODS

Date from 214 PTC patients (cN0) who underwent partial or total thyroidectomy and pCLND at the Guizhou Provincial People's Hospital were collected and retrospectively analyzed. They were divided into two groups in accordance with cervical CLNM or not. Their information, including clinical characteristics, ultrasound (US) features, pathological results of fine-needle aspirations biopsy (FNAB), and other characteristics of the groups, was analyzed and compared using univariate and multivariate logistic regression analyses.

RESULTS

A total of 214 patients were eligible in this study. Among them, 43.5% (93/214) of PTC patients had cervical CLNM, and 56.5% (121/214) did not. The two groups were compared using a univariate analyses, and there were no significant differences between the two groups in aspect ratio, boundary, morphology, component, and BRAFV600E (P > 0.05), and there were significant differences between gender, age, maximum tumor size, tumor location, capsule contact, microcalcifications, color Doppler flow imaging (CDFI), and Hashimoto's thyroiditis (HT) (P < 0.05). A multivariate logistic regression analysis was performed to further clarify the correlation of these indices. However, only age (OR = 2.455, P = 0.009), maximum tumor size (OR = 2.586, P = 0.010), capsule contact (OR = 3.208, P = 0.001), and CDFI (OR = 2.225, P = 0.022) were independent predictors of cervical CLNM. Combining these four factors, the area under the receiver-operating characteristic (ROC) curve for the joint diagnosis is 0.8160 (95% 0.7596-0.8725). Univariate analysis indicated that capsule contact (P = 0.001) was a possible predictive factor of BRAFV600E mutation.

CONCLUSIONS

In conclusion, four independent predictors of cervical CLNM, including age < 45 years, tumor size > 1.0 cm, capsule contact, and rich blood flow, were screened out. Therefore, a comprehensive assessment of these risk factors should be conducted when designing individualized treatment regimens for PTC patients.

Clinical role of 18F-FDG PET/CT for detection of radioactive iodine refractory differentiated thyroid cancer

In clinical settings, an estimated 10% differentiated thyroid cancer (DTC) cases become radioactive iodide refractory (RAIR), which lack a molecular marker and have fewer treatment selections. A higher uptake of 18F-fluorodeoxyglucose (18F-FDG) might indicate poor prognosis for DTC. This study aimed to evaluate the clinical value of 18F-FDG psitron emission tomography/computed tomography (PET/CT) for the early diagnosis of RAIR-DTC and high-risk DTC. A total of 68 DTC patients were enrolled and underwent 18F-FDG PET/CT for the detection of recurrence and/or metastasis. 18F-FDG uptake was evaluated in patients with different postoperative recurrence risks or TNM stages and compared between RAIR and non-RAIR-DTC based on its maximum standardized uptake value and tumor/liver (T/L) ratio. The final diagnosis was judged by histopathology and follow-up data. Of 68 DTC cases, 42 were RAIR and 24 non-RAIR, with 2 not determined. A total of 263 of 293 lesions detected on 18F-FDG PET/CT were confirmed to be locoregional or metastatic after follow-up. The T/L ratio was significantly higher for RAIR than for non-RAIR (median 5.18 vs 1.44; P < .01) and also significantly higher in postoperative patients at high-risk of recurrence than at low to medium risk (median 4.90 vs 2.16; P < .01). 18F-FDG PET/CT exhibited a sensitivity of 83.3% and specificity of 87.5% for identifying RAIR, with a cutoff T/L value of 2.98. 18F-FDG PET/CT has the potential to diagnose RAIR-DTC early and identify the high-risk DTC. The T/L ratio is a useful parameter for the detection of RAIR-DTC patients.

Analysis of Radiometry on Patients Undergoing Radioactive Iodine Therapy

The treatment for differentiated thyroid cancer consists of thyroidectomy followed by radioactive iodine therapy (RIT), in which the patient remains in isolation until the dose rate of the radioactive iodine reduces to a certain limit. The present research intends to estimate the length of stay of patients who undergo RIT, with radiometry analysis performed throughout the patient's admission. Methods: Information such as age, sex, weight, height, prescribed activity, volume of liquids ingested, and the use of recombinant human thyrotropin was gathered from 204 patients with differentiated thyroid cancer who underwent RIT. During the admission, the dose rate was periodically measured. The data served as variables for a multiple regression, in which the coefficients (the term coefficient in this paper is related to the multiplicative factor of each considered variable used in Eqs. 1-4) and significance of each were verified as a function of the dose rate. Results: The results showed that length of stay, administered activity, volume of liquids ingested, use of recombinant human thyrotropin, and patient weight impacted significantly on the dose rate. The average effective half-life of the ¹³¹I, considering all patients, was 12.61 ± 3.28 h, and the average time for their radiologic release was 15.23 ± 5.50 h. On the basis of the results, it was possible to develop a tool to estimate a patient's length of stay and effective half-life. Conclusion: The results can contribute to optimization of the radiologic protection of patients who undergo RIT, as well as allow better logistics regarding their admission, which can lead to more appropriate accommodation for the patient and a better use of resources.