Low-risk Differentiated Thyroid Cancer Research Articles

Rethinking on the epidemic situation and standardized diagnosis and treatment of low risk differentiated thyroid cancer

Thyroid cancer is a malignant tumor originating from thyroid epithelial or parafollicular epithelial cells. It is also the most common malignant tumor in the head and neck. At present, the incidence of thyroid cancer ranks ninth among all common malignant tumors, and has become one of the top ten common malignant tumors. In recent years, with the release of various guidelines, the diagnosis and treatment of thyroid cancer around the world is gradually standardized. Meanwhile, China has also begun to implement quality control of diagnosis and treatment, standardize diagnosis and treatment behavior, and promote the standardization of diagnosis and treatment of thyroid tumors nationwide, in order to ultimately improve patient's survival rate and quality of life. Based on the current changes in the diagnosis and treatment of thyroid cancer at home and abroad, the article discusses the epidemic situation, diagnosis and treatment status, new concept and progress of standardized diagnosis and treatment of thyroid cancer.

Outcomes of Low-Risk Differentiated Thyroid Cancer (DTC) without Radioactive Iodine (RAI) Ablation Therapy Post-Thyroidectomy: An Experience from a Tertiary Centre in Karachi.

To assess the outcomes of low-risk differentiated thyroid cancer (DTC) with tumour size 1 to 4 cm post-thyroidectomy in patients who never received radioactive iodine (RAI) ablation and to compare the outcomes with those who received RAI therapy. Observational study. Place and Duration of the Study: Department of Nuclear Medicine, Karachi Institute of Radiotherapy and Nuclear Medicine (KIRAN) Hospital, Karachi, Pakistan, from January 2016 to December 2020. A total of 130 consecutive patients of low-risk DTC of both genders aged between 18-75 years were identified who underwent thyroidectomy. Patients were classified as either being treated or not treated with RAI, based on RAI data post-thyroidectomy. Patients were followed up for two to five years depending on their date of diagnosis from 2016 to 2020, using thyroglobulin (Tg), anti-thyroglobulin (anti-Tg), and thyrotropin (TSH) levels and ultrasound neck. Association betweenpatients who received RAI and who did not receive RAI was determined and a p-value<0.05 was considered as statistical significance. Patients had mean age of 34.5 ± 10.4 years with majority of females (75.4%). Majority of the patients (94.6%) had total thyroidectomy with no neck dissection (83.1%). RAI therapy was conducted among 70.8% participants, of which, 56.9% participants received a dose of 100 mci. Most of the patients had positive outcomes as there was no recurrence among 96.2% participants. There was a significant difference in RAI therapy with total thyroidectomy as compared to subtotal, RAI dose, tumour stage, neck dissection, and lymph node involvement (p ≤0.001). After complete tumour resection, a highly selected group of patients with low-risk local disease have shown low rate of recurrence when managed without RAI. Interestingly, the disease recurrence was also only seen in patients who received RAI therapy in comparison to those who did not receive RAI therapy. Outcomes, Differentiated thyroid cancer, Radioactive iodine, Ablation therapy, Post-surgery.

Reoperation Rates after Initial Thyroid Lobectomy for Patients with Thyroid Cancer: A National Cohort Study.

Introduction The 2015 ATA guidelines recommended thyroid lobectomy (TL) as an alternative to total thyroidectomy (TT) for the surgical treatment of low-risk differentiated thyroid cancer. Increasing use of TL has since been reported despite concerns for an increased risk of disease recurrence and need for reoperation. This study sought to compare reoperation rates among patients who underwent initial TL or TT for malignancy, characterize trends at centers based on operative volume, and examine factors associated with reoperation. Methods We queried the Vizient Clinical Data Base for TL and TT performed pre-guideline change (pre-GC=2013-2015) and post-guideline change (post-GC=2016-2021). Reoperations included reoperative thyroid surgery (RTS) and neck dissection (ND); timing was defined as early (180 days), thought to indicate inadequacy of initial operative choice, or late (>180 days), suggesting disease recurrence. Results Of 65,627 patients, 31.8% underwent initial TL and 68.2% underwent initial TT; TL increased from 21.4% of total cases pre-GC to 37.0% post-GC (p<0.001). Among TL patients, early RTS declined from 33.9%-14.2% and ND declined from 0.8%-0.4% (p<0.001). Among TT patients, early RTS remained 0.2%, while ND increased from 0.4%-0.7% (p<0.001). TL-associated late RTS declined from 2.0%-1.7%, while ND increased from 0.6%-0.8% (p=0.17). In TT patients, both late RTS and ND increased, from 0.2%-0.3% (p=0.04) and 1.7%-2.1% (p<0.01), respectively. There was no difference in the late reoperation rate for TL compared to TT post-GC (+0.2%, p=0.18). TL volume grew annually by 12.5% [8.9%-16.2%] at high-volume centers and 8.3% [5.6%-11.1%] at low-volume centers. TL-associated reoperations at high-volume centers declined annually by 12.6% [5.6%-19.0%] and 10.8% [2.7%-18.1%] at low-volume centers. Uninsured status and more recent initial operation were associated with an increased risk of late reoperation (HR=1.84 [1.06-3.20] and HR=1.30 [1.24-1.36], respectively). The type of index operation performed, however, was not predictive of late reoperation. Conclusions The rate of early reoperations declined for thyroid lobectomy after the 2015 ATA guideline release but late reoperations remained unchanged despite a significant shift in practice patterns towards performing initial lobectomy. Patients appear to be receiving less aggressive, guideline-concordant care without a significant increase in the late reoperation rate for thyroid lobectomy compared to total thyroidectomy.

Differential Utilization of Thyroid Lobectomy After the 2015 American Thyroid Association Guideline Update

Background: The 2015 ATA Guidelines added thyroid lobectomy (TL) as appropriate treatment for low-risk differentiated thyroid cancer (DTC). We aimed to investigate the population-level factors that influence utilization of TL. Methods: The Surveillance, Epidemiology and End Results (SEER) database was queried for all DTC patients fitting low risk criteria as defined by the ATA. Trends in TT and TL were identified using a Cochrane-Armitage test. Multivariable logistic regression identified patient and socioeconomic characteristics associated with TL, and difference-in-difference analysis was used to control for secular trends over time. Results: A total of 43,526 patients with low-risk DTC were identified in the SEER database; 39,411 pre-2015 and 4,115 post-2015. After 2015, TT continued to outnumber TL (76.2% vs. 23.8%), although the rate of TL increased significantly (11.6% to 23.8%, p &lt; 0.001). However, difference-in-difference analysis found that age &gt; 55 (OR 1.11, 95% CI 1.01-1.19, p&lt;0.001) and rurality (OR 1.16, 95% CI 1.05-1.28, p&lt;0.001) were independently associated with TT. TL was associated with T1 disease (OR 1.11, 95% CI 1.04-1.19, p=0.001). Conclusions: Although the 2015 ATA guideline update led to an increase in TL for low-risk DTC, most patients still underwent TT. Age and neighborhood significantly impact the odds of receiving guideline-appropriate TL for low-risk DTC, especially for T2 disease.

Editorial sobre “Nuevas perspectivas en el manejo del cáncer de tiroides de bajo riesgo. Experiencia con la lobectomía tiroidea en una cohorte de 114 pacientes”

As the authors of the paper state, the management of low-risk differentiated thyroid cancer (DTC) remains controversial because of the indolent nature of the disease and the challenge of balancing morbidity of treatments with the risk of disease progression. The extent of thyroid resection is still a matter of debate: total thyroidectomy (TT) versus hemithyroidectomy (HT) (lobectomy plus isthmusectomy) using either a conventional neck incision or, in selected patients, a remoteaccess procedure, in this case the Transoral Endoscopic Thyroidectomy Vestibular Approach (TOETVA)1 . In the article published in this issue, Sacco et al. report the results of an observational study analyzing retrospective data obtained from the electronic medical records of a cohort of 114 patients with low-risk DTC managed with HT though different surgical approaches (neck incision and remote transoral approach) between January 2015 and April 2023. The number of TH proced

Nuevas perspectivas en el tratamiento del cáncer de tiroides de bajo riesgo. Experiencia con la lobectomía tiroidea en una cohorte de 114 pacientes

Background: The treatment of low-risk differentiated thyroid cancer (DTC) is still a matter of debate. Over the past few decades, there has been a shift towards a more personalized approach, tailored to the individual risks of each patient and tumor. The current practice guidelines recommend lobectomy in selected patients, with low risk of recurrence. Objective: To describe the results of thyroid lobectomy in a cohort of patients with DTC with low risk of recurrence. Material and methods: We conducted a descriptive and observational study. The medical records of patients with DTC who underwent thyroid lobectomy between January 2015 and April 2023 were retrospectively reviewed. Results: A total of 114 patients were operated on; mean age was 44 ± 12 years and 90 (79%) were women. The median tumor size was 9.4 mm (IQR 25-75% 7-13 mm), and 103 nodules (90%) were solid on ultrasound. Only 2 patients with vascular invasion involving &gt; 4 vessels required completion thyroidectomy. There were no major complications and only one patient developed temporary recurrent laryngeal palsy. There were no locoregional or distant recurrences during mean follow-up of 33.4 months. Conclusion: Thyroid lobectomy for low-risk DTC had low morbidity and no recurrences in the series presented. The rigorous selection of patients and the interaction of a multidisciplinary team are considered essential for the successful implementation of this therapeutic approach.

Clinical inertia in thyrotropin suppressive therapy for low-risk differentiated thyroid cancer: A real-world experience at an endocrine center in Bangkok.

The management of low-risk differentiated thyroid cancer (DTC) has evolved over time toward treatment de-escalation. However, overtreatment with supraphysiological dose of levothyroxine (LT4) continues to be observed despite current clinical guideline. This study aimed to assess the actual thyrotropin suppressive therapy for low-risk DTC patients at an endocrine center in Bangkok. This retrospective study included patients with low-risk DTC who were regularly follow-up for at least 18 months at Theptarin Hospital between 2016 and 2022. The serum thyroid stimulating hormone (TSH) levels were stratified as TSH < 0.1 mIU/L; TSH 0.1 to 0.5 mIU/L; TSH 0.5 to 2.0 mIU/L; and TSH > 2.0 mIU/L. The initial risk stratification (IRS) and dynamic risk stratification were determined at 12 months of follow-up after completing the initial treatment and at the last visit. The clinical factors associated with overtreatment with LT4 were analyzed. A total of 102 patients (83.3% female, age at diagnosis 41.8 ± 13.6 years, mean tumor size 1.6 ± 1.0 cm) were evaluated with a mean follow-up of 5.9 years. The IRS classified 92.2% of patients after the initial treatment and 93.1% of patients at the last follow-up visit into the excellent response category. The mean LT4 daily dosage at the last follow-up was 121.3 ± 44.8 µg/day. Serum TSH levels were in an appropriate target range according to IRS in only 8.8% (9/102) of the patients and then improved to 19.6% (20/102) at the last follow-up visit. Further analysis showed that treating physicians with ≥10 years of practice was associated with severe TSH suppression therapy (TSH < 0.1 mIU/L). Despite the current clinical guideline recommendations and scientific evidences, less than one-fifth of low-risk DTC patients achieved the appropriate serum TSH target. While the proportion of an optimum LT4 suppressive had improved during the study period, further efforts are needed to overcome this clinical inertia.

The effect of COVID-19 pandemic restrictions on the management of differentiated thyroid cancer in Turkey: a single tertiary centre experience.

Many countries have implemented unprecedented health measures since the World Health Organisation declared the novel coronavirus disease 2019 (COVID-19) a global pandemic. These measures have resulted in delays in the diagnosis of differentiated thyroid cancer (DTC). However, there is limited data on the impact of restrictions imposed during the pandemic on DTC management. Thus, the aim of this study is to analyse the clinicopathological and follow-up data of DTC patients diagnosed before and during the COVID-19 outbreak. This retrospective study included 191 DTC patients that were diagnosed between December 2018 and June 2021. The patients were divided into two groups: patients diagnosed before (December 2018 to February 2020) and during (March 2020 to June 2021) the COVID-19 pandemic. The clinicopathological and follow-up data between the two groups were compared. Similar preoperative cytology results were obtained from the two groups. No difference with regard to tumour size, lymphovascular invasion and extrathyroidal invasion was observed between the two groups. While the American Thyroid Association risk stratification was similar between the two groups, radioactive iodine (RAI) therapy was applied less during the COVID-19 period. Although RAI therapy was administered at a lower rate during the COVID-19 period, the recurrence rates among patients after two years of follow-up were similar to those during the pre-COVID-19 period. Although the COVID-19 pandemic restrictions during the pandemic period caused difficulties in the management of DTC patients, this did not negatively affect their prognosis. These findings can confirm the applicability of active surveillance in DTC patients and may help change the real-life treatment practices in selected low-risk DTC patients.

All-Cause and Cause-Specific Mortality Among Low-Risk Differentiated Thyroid Cancer Survivors in the United States.

Background: Despite the excellent disease-specific survival associated with low-risk differentiated thyroid cancer (DTC), its diagnosis and management have been linked to patient concerns about cancer recurrence, treatment-related health risks, and mortality. Lack of information regarding long-term health outcomes can perpetuate these concerns. Therefore, we assessed all-cause and cause-specific mortality in a large cohort of individuals diagnosed with low-risk DTC. Methods: From the U.S. Surveillance, Epidemiology, and End Results-12 cancer registry database (1992-2019), we identified 51,854 individuals (81.8% female) diagnosed with first primary DTC at low risk of recurrence (≤4 cm, localized). We estimated cause-specific cumulative mortality by time since diagnosis, accounting for competing risks. Standardized mortality ratios (SMRs) and CIs were used to compare observed mortality rates in DTC patients with expected rates in the matched U.S. general population, overall and by time since DTC diagnosis. We used Cox proportional hazards models to examine associations between radioactive iodine (RAI) treatment and cause-specific mortality. Results: During follow-up (median = 8.8, range 0-28 years), 3467 (6.7%) deaths were recorded. Thyroid cancer accounted for only 4.3% of deaths (n = 148). The most common causes of death were malignancies (other than thyroid cancer) (n = 1031, 29.7%) and cardiovascular disease (CVD; n = 912, 26.3%). The 20-year cumulative mortality rate from thyroid cancer, malignancies (other than thyroid or nonmelanoma skin cancer), and CVD was 0.6%, 4.6%, and 3.9%, respectively. Lower than expected mortality was observed for all causes excluding thyroid cancer (SMR = 0.69 [CI 0.67-0.71]) and most specific causes, including all malignancies combined (other than thyroid cancer; SMR = 0.80 [CI 0.75-0.85]) and CVD (SMR = 0.64 [CI 0.60-0.69]). However, mortality rates were elevated for specific cancers, including pancreas (SMR = 1.58 [CI 1.18-2.06]), kidney and renal pelvis (SMR = 1.85 [CI 1.10-2.93]), and brain and other nervous system (SMR = 1.62 [CI 0.99-2.51]), and myeloma (SMR = 2.35 [CI 1.46-3.60]) and leukemia (SMR = 1.62 [CI 1.07-2.36]); these associations were stronger ≥10 years after diagnosis. RAI was not associated with risk of cause-specific death, but numbers of events were small and the range of administered activities was likely narrow. Conclusions: Overall, our findings provide reassurance regarding low overall and cause-specific mortality rates in individuals with low-risk DTC. Additional research is necessary to confirm and understand the increased mortality from certain subsequent cancers.

Abstract #1568836: Outcomes of Patients With Low-Risk Differentiated Thyroid Cancer (DTC) Without Radioactive Iodine (RAI) Ablation Therapy Postsurgery: An Experience From a Tertiary Center in Karachi

Abstract #1568836: Outcomes of Patients With Low-Risk Differentiated Thyroid Cancer (DTC) Without Radioactive Iodine (RAI) Ablation Therapy Postsurgery: An Experience From a Tertiary Center in Karachi

Practice patterns in management of differentiated thyroid cancer since the 2014 British Thyroid Association (BTA) guidelines

BackgroundThe updated 2014 BTA guidelines emphasised a more conservative, risk adapted model for the management of low-risk differentiated thyroid cancer (DTC). In comparison to historical approach of total thyroidectomy combined with radioactive iodine, treatment de-escalation is increasingly supported. AimsTo evaluate the impact of the updated BTA guidelines on the management of DTC cases at regional UK centre. MethodsAll DTC patients were retrospectively identified from regional thyroid MDT database between Jan2009–Dec2020. Oncological treatment and clinico-pathological characteristics were analysed. Results623 DTC cases were identified; 312 (247 female: 65 male) between 2009 and 2014 and 311 (225 female: 86 male) between 2015 and 2020. Median age is 48 years (range 16–85). By comparing pre- and post-2015 cohorts, there was a significant drop in total thyroidectomy (87.1% vs 76.8%, p = 0.001) and the use of radioactive iodine (RAI) (73.1% vs 62.1%, p = 0.003) in our post-2015 cohort. When histological adverse features were analysed, extra-thyroidal extension (4.2% vs 17.0%, p=< 0.001), lymphovascular invasion (31.4% vs 50.5%, p=<0.001) and multi-centricity (26.9% vs 43.4%, p = 0.001) were significantly increased in the post 2015 cohort. Nonetheless, total thyroidectomy (TT) remains the treatment choice for low risk T1/2 N0 M0 disease in 65.3% (124/190) in post-2015 cohort for several reasons. Reasons include adverse histological features (50.8%), benign indications (32.5%), contralateral nodules (11.7%), patient preference (2.5%), and diagnostic uncertainty (2.5%). ConclusionOur study confirms a move towards a more conservative approach to patients with low-risk DTC in the UK, which is in keeping with the BTA 2014 guideline and international trends, but total thyroidectomy remains prevalent for low risk T1/2 N0 M0 disease for other reasons.

SAT526 Limited Utility of Routine Neck Ultrasound Follow-up in Advanced Stage Differentiated Thyroid Cancer

Abstract Disclosure: V. Munro: None. S. Mustafa: None. F.S. Siddiqi: None. M. Rajaraman: None. S.A. Imran: None. Background: Most guidelines recommend periodic cervical ultrasound (US) for ongoing surveillance of differentiated thyroid cancer (DTC). While recent studies do not support routine US surveillance in low-risk DTC, to date, no study has assessed the clinical utility of cervical US in advanced DTC. Methods: We conducted a retrospective study of our hospital DTC registry using the following criteria: a) AJCC stage III and IV, b) minimum follow-up of &amp;gt;4 years since total thyroidectomy +/-I-131 ablation, and c) at least one US per 3 years of follow-up. Patients with hemithyroidectomy only or positive anti-thyroglobulin antibody at the initial visit were excluded. Two years after initial treatment, patients were categorized by Dynamic Risk Stratification (DRS) as excellent, indeterminate, biochemically incomplete, or structurally incomplete response. Data obtained at each visit included: treatment response, thyroglobulin (TG) level, and US findings. Results: A total of 114 patients (85 AJCC stage III and 29 stage IV patients) met the inclusion criteria. Mean age (yrs) at diagnosis was 59, and 67% were female. Mean duration of follow-up was 8.5 years. Based on DRS, 73 patients had excellent response, 28 indeterminate, 8 biochemically incomplete, and 5 structurally incomplete. Recurrence or progression was detected in 20 patients (17.5%): 5 excellent response, 6 indeterminate, 5 biochemically incomplete, and 4 structurally incomplete. Recurrence sites included cervical region (14), distant metastases (5) and both (1). The TG rose from a mean of 4.76 ng/mL at baseline to 40.37 ng/mL at time of recurrence/progression. In those with structurally incomplete disease, US demonstrated progression in all 4 patients. However in other DRS categories, only 5/10 had definite US abnormalities. Of those without recurrence, 4 patients (4.3%) had false positive TG (mean baseline TG 0.08 rose to 11.8 ng/ml) without clinical/radiologic recurrence whereas the rate of false positive US abnormalities was 32% (37/114). The sensitivity and specificity of US vs. TG in diagnosing recurrence was 45% and 60% vs 100% and 95.7%, respectively. Conclusion: Our study suggests that routine cervical US surveillance after initial DRS does not improve the detection of recurrence in patients with excellent, indeterminate, or biochemically incomplete disease, and has a high false positive rate. Therefore, we suggest TG should be considered the mainstay of surveillance and any further imaging guided by DRS status and change in TG. Presentation Date: Saturday, June 17, 2023

2212MO Major secondary outcomes in the multicentre noninferiority randomised trial IoN: Is ablative radioiodine necessary for low-risk differentiated thyroid cancer patients?

2212MO Major secondary outcomes in the multicentre noninferiority randomised trial IoN: Is ablative radioiodine necessary for low-risk differentiated thyroid cancer patients?

Contemporary trends in extent of surgery for differentiated thyroid cancer with extrathyroidal extension

ObjectiveAlthough lobectomy is acceptable for patients with small, low-risk differentiated thyroid cancer (DTC), gross extrathyroidal extension (ETE) remains an indication for total thyroidectomy (TT). Here we investigate evolving trends in extent of surgery for ​+ ​ETE DTC. MethodsPatients with +ETE DTC who underwent resection from 2010 to 2020 were identified using the National Cancer Database. The primary outcome was performance of TT versus lobectomy. ResultsAmong 5851 patients, most were female (79.7%), white (80.0%), and had minimal ETE (91.8%). Ninety-two percent of patients received TT. Year of treatment was influential (p ​< ​0.001), with increasing lobectomy rates in later years. On multivariable analyses, a decreased likelihood of TT was seen in years 2015 through 2020. ConclusionsMost patients with +ETE DTC underwent guideline-concordant TT, but lobectomy rates doubled over the study period. These findings may reflect increased preference for lobectomy in low-risk DTC, but could undertreat patients with high-risk features.

Lobectomy outcomes in patients with low-risk differentiated thyroid cancer: oncologic and safety outcomes at a swiss tertiary referral center

Lobectomy outcomes in patients with low-risk differentiated thyroid cancer: oncologic and safety outcomes at a swiss tertiary referral center

A Qualitative Look at Influential Factors in Decision Making among Patients with Low-Risk Differentiated Thyroid Cancer

A Qualitative Look at Influential Factors in Decision Making among Patients with Low-Risk Differentiated Thyroid Cancer

The effects of reoperations due to inadequate treatment in differentiated thyroid cancers on morbidity, mortality and costs

Although the incidence of differentiated thyroid cancer (DTC) is high, mortality is quite low. In low and intermediate risk DTCs, reoperations due to inadequate treatment can increase morbidity, mortality, and costs in patients. In our study, current articles published on this subject were reviewed and evaluated. According to our results, morbidity, mortality and costs increase due to inadequate treatment in DTCs. Therefore, even in low and intermediate risk DTC cases, adequate surgeries such as total or near total thyroidectomy should be performed by high volume endocrine surgeons and moderate TSH suppression should be applied in all cases.

Outcomes of ATA Low-Risk Pediatric Thyroid Cancer Patients Not Treated With Radioactive Iodine Therapy.

The American Thyroid Association (ATA) Pediatric Guidelines recommend patients not receive radioactive iodine therapy (RAIT) for differentiated thyroid cancer (DTC) confined to the thyroid. Since publication, there is ongoing concern whether withholding RAIT will result in a lower rate of remission. This study explores whether ATA low-risk patients treated with and without RAIT achieved similar remission rates. Medical records of patients <19 years old diagnosed with DTC and treated with total thyroidectomy between 2010 and 2020 were reviewed. Multivariate logistic regression was performed to evaluate factors influencing RAIT administration and remission rate. Ninety-five patients with ATA low-risk DTC were analyzed: 53% (50/95) and 47% (45/95) were treated with and without RAIT, respectively. RAIT was used to treat 82% of patients before 2015 compared with 33% of patients after 2015 (P < .01). No significant difference in 1-year remission rate was found between patients treated with and without RAIT, 70% (35/50) vs 69% (31/45), respectively. With longer surveillance, remission rates increased to 82% and 76% for patients treated with and without RAIT, respectively. Median follow-up was 5.8 years (IQR 4.3-7.9, range 0.9-10.9) and 3.6 years (IQR 2.7-6.6; range 0.9-9.3) for both cohorts. No risk factors for persistent or indeterminate disease status were found, including RAIT administration, N1a disease, and surgery after 2015. Withholding RAIT for pediatric patients with ATA low-risk DTC avoids exposure to radiation and does not have a negative impact on remission rates. Dynamic risk stratification at 1-year after initial treatment is a suitable time point to assess the impact of withholding RAIT for these patients.

Comparison of Radioactive Iodine Activities in Terms of Short- and Long-term Results in Ablation Therapy in Patients with Low-risk Differentiated Thyroid Cancer.

The aim of this study was to compare the treatment responses after ablation with 30-50 mCi radioactive iodine (RAI) and 100 mCi RAI in patients with differentiated thyroid cancer (DTC) who were in the low-risk group according to 2015 American Thyroid Associations Classification (ATA 2015) criteria. Between February 2016 and August 2018, 100 patients who received RAI treatment in our clinic after total thyroidectomy and who were in the low-risk group DTC were included in this retrospective study. These patients were divided into 2 groups: low-activity (30-50 mCi) (group 1) and high-activity (100 mCi) (group 2). While 54 patients were treated with low activity, 46 patients received high activity RAI. The 2 groups were compared according to the 1st- and 3rd-year treatment response status. According to the first-year follow-up, 15 patients were accepted as indeterminate response and 85 patients as excellent response. Three (5.5%) of the patients who were accepted as indeterminate response were in group 1 and 12 (26%) were in group 2. According to the third year follow-up, 1 patient in group 1 and 3 patients in group 2 were accepted as indeterminate response. No biochemical incomplete response or recurrent disease was detected. In the chi-square analysis performed to investigate the relationship between the first-year treatment response and RAI activities, a significant relationship was found (p=0.004). In the Mann-Whitney U test performed to investigate the parameters that may be effective in the treatment response, only the preablative serum thyroglobulin value was shown to have a significant difference between the two groups (p=0.01). In the long-term follow-up of the patients, based on the third year treatment response data, chi-square analysis was performed to evaluate the two groups in terms of treatment responses, and no statistically significant relationship was found (p=0.73). Ablation with 30-50 mCi can be safely applied in DTC patients who are in the ATA 2015 low-risk group and are planned for RAI ablation treatment.

EE384 Cost-Effectiveness of Hemithyroidectomy Versus Total Thyroidectomy for Patients with Low Risk Differentiated Thyroid Cancer

The 2015 American Thyroid Association (ATA) guidelines recommended hemithyroidectomy as initial treatment for smaller (1-4 cm) primary thyroid carcinomas, particularly for papillary and follicular thyroid cancer. This research aims to examine whether hemithyroidectomy for patients with low risk differentiated thyroid cancer is cost-effective relative to total thyroidectomy from a modified societal perspective.