Materials and Methods
The present report updates our experience since the earlier study. We performed a retrospective analysis of medical charts of RAI-avid patients with metastatic thyroid cancer in follow-up at MedStar Washington Hospital Center and MedStar Georgetown University Hospital from 1996 to 2017. The study group was subdivided into those prepared for RAI therapy by THW alone or with rhTSH alone. The former group was off thyroid hormone for at least 4 weeks, while the latter was given rhTSH 0.9 mg intramuscularly for 2 consecutive days, followed by a therapeutic activity of 131I within 24 to 30 hours. The mode of preparation was chosen based on the attending physician's preference. A posttherapy scan was performed after 7 to 10 days. TSH levels at the time of therapy were documented for both groups. All patients were instructed to follow a low-iodine diet for at least 2 weeks before RAI therapy, and urine iodine levels were checked for compliance prior to therapy. A subset of patients that had a prior RAI therapy prepared with THW and subsequently with rhTSH is described separately. The study was approved by the MedStar Health Research Institutional Review Board.
Response to therapy was assessed according to the revised RECIST 1.1 criteria. Complete response (CR) is defined by the disappearance of all target lesions, while partial response (PR) corresponds to at least a 30% reduction in the sum of their diameters. Progressive disease (PD) represents at least a 20% increase in the sum of diameters of target lesions, taking the smallest sum documented as a reference. Stable disease (SD) represents neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD. PFS was assessed from the date of last RAI therapy to the date of a computed tomography or magnetic resonance imaging scan confirming progression of target lesions. OS was considered the interval between the last follow-up and the first radioiodine therapy. The primary end point of this study was difference in PFS between the groups. The secondary end point was OS.
All data extracted from electronic medical records were summarized using descriptive statistics such as mean with SDs or medians and range for continuous variables, and frequencies and percentages for categorical variables. Continuous variables were compared by 2-sample t test and Wilcoxon rank sum test as appropriate, while categorical variables were compared by chi-square and Fisher exact tests as appropriate. Kaplan-Meier curves were provided for OS and PFS, and log rank test was used to compare the curves. Multivariate Cox proportional hazards models were conducted controlling for the independent variables that were significant in the bivariate analysis to examine the risk of progression and risk of death. Statistical significance was defined as P less than or equal to .05. Analyses were performed with SAS 9.4 (SAS Institute Inc).
J Endo Soc. 2022;6(5) © 2022 Endocrine Society