Danielle L James1,2, Éanna J Ryan1,3,4, Matthew G Davey1,3, Alanna Jane Quinn1,2, David P Heath1, Stephen James Garry2,4, Michael R Boland1,4, Orla Young2, Aoife J Lowery1,3, Michael J Kerin1,3. 1. Department of Surgery, Galway University Hospitals, Galway, Ireland. 2. Department of Otorhinolaryngology, Head & Neck Surgery, Galway University Hospitals, Galway, Ireland. 3. The Lambe Institute for Translational Research, National University of Ireland, Galway, Galway, Ireland. 4. Department of Surgery, The Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin, Ireland.
Abstract
Importance: Postoperative radioactive iodine (RAI) remnant ablation for differentiated thyroid cancer (DTC) facilitates the early detection of recurrence and represents an adjuvant therapy that targets persistent microscopic disease. The optimal activity of RAI in low- and intermediate-risk DTC remains controversial. Objective: To evaluate the long-term cure rate of different RAI activities in low- and intermediate-risk DTC. Secondary outcomes included successful remnant ablation, adverse effects, and hospital length of stay. Data Source: A systematic search of the databases PubMed, Cochrane Collaboration, Embase, Scopus, and Web of Science was performed to identify randomized clinical trials (RCTs) and observational studies that compared long-term outcomes (>12 months) for American Thyroid Association-classified low- and intermediate-risk DTC based on receipt of either low-activity or high-activity RAI postoperatively. Study Selection: All RCTs or observational studies evaluating patients with low- and intermediate-risk DTC who were treated initially with total/near-total thyroidectomy, followed by remnant RAI ablation with either low or high activities. Eligible studies had to present odds ratio, relative risk (RR), or hazard ratio estimates (with 95% CIs), standard errors, or the number of events necessary to calculate these for the outcome of interest rate. Data Extraction: Two investigators reviewed the literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Dichotomous variables were pooled as risk ratios and continuous data as weighted-mean differences. Quality assessment of the included studies was performed using the Newcastle-Ottawa and Jadad scales. Main Outcomes and Measures: Disease recurrence was the primary outcome. Secondary outcomes included successful ablation, adverse effects, and length of stay. Results: Ten studies that included 3821 patients met inclusion criteria, including 6 RCTs and 4 observational studies. There was no difference in long-term cure recurrence rates (RR, 0.88; 95% CI, 0.62-1.27, P = .50) or successful remnant ablation (RR, 0.95; 95% CI, 0.87-1.03; P = .20) between low-activity and high-activity RAI. Conclusions and Relevance: In this systematic review and meta-analysis, low-activity RAI was comparable with high-activity RAI regarding successful ablation and recurrence rates. This suggests that low-activity RAI is preferable to high-activity in low- and intermediate-risk DTC because of its similar efficacy but reduced morbidity. Trial Registration: PROSPERO Identifier: CRD42020166780.
Importance: Postoperative radioactive iodine (RAI) remnant ablation for differentiated thyroid cancer (DTC) facilitates the early detection of recurrence and represents an adjuvant therapy that targets persistent microscopic disease. The optimal activity of RAI in low- and intermediate-risk DTC remains controversial. Objective: To evaluate the long-term cure rate of different RAI activities in low- and intermediate-risk DTC. Secondary outcomes included successful remnant ablation, adverse effects, and hospital length of stay. Data Source: A systematic search of the databases PubMed, Cochrane Collaboration, Embase, Scopus, and Web of Science was performed to identify randomized clinical trials (RCTs) and observational studies that compared long-term outcomes (>12 months) for American Thyroid Association-classified low- and intermediate-risk DTC based on receipt of either low-activity or high-activity RAI postoperatively. Study Selection: All RCTs or observational studies evaluating patients with low- and intermediate-risk DTC who were treated initially with total/near-total thyroidectomy, followed by remnant RAI ablation with either low or high activities. Eligible studies had to present odds ratio, relative risk (RR), or hazard ratio estimates (with 95% CIs), standard errors, or the number of events necessary to calculate these for the outcome of interest rate. Data Extraction: Two investigators reviewed the literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Dichotomous variables were pooled as risk ratios and continuous data as weighted-mean differences. Quality assessment of the included studies was performed using the Newcastle-Ottawa and Jadad scales. Main Outcomes and Measures: Disease recurrence was the primary outcome. Secondary outcomes included successful ablation, adverse effects, and length of stay. Results: Ten studies that included 3821 patients met inclusion criteria, including 6 RCTs and 4 observational studies. There was no difference in long-term cure recurrence rates (RR, 0.88; 95% CI, 0.62-1.27, P = .50) or successful remnant ablation (RR, 0.95; 95% CI, 0.87-1.03; P = .20) between low-activity and high-activity RAI. Conclusions and Relevance: In this systematic review and meta-analysis, low-activity RAI was comparable with high-activity RAI regarding successful ablation and recurrence rates. This suggests that low-activity RAI is preferable to high-activity in low- and intermediate-risk DTC because of its similar efficacy but reduced morbidity. Trial Registration: PROSPERO Identifier: CRD42020166780.