Time Interval Between First and Second Radioiodine Treatment in Differentiated Thyroid Carcinoma: The Contribution of Patient and Disease Factors to Interval Variability
Keywords:
Differentiated thyroid carcinoma, Radioiodine therapy, Time to retreatment, Timeliness of care, Retrospective studyAbstract
This study was survey research by retrospective study aimed to described the distribution of the interval between the first and second courses of radioiodine treatment and examined how much of its variance is explained by patient and disease factors. A secondary analysis of a retrospective cohort of 111 patients with differentiated thyroid carcinoma treated at Udon Thani Cancer Hospital between 2022 and 2025 was performed, using descriptive statistics, Wilson confidence intervals, and multiple linear regression on the log-transformed interval with HC3 robust standard errors.
The median interval was 8.61 months (interquartile range 7.13-11.04). Treatment occurred within the 6- to 12-month window in 74.8% of patients (95% CI, 66.0-81.9) and beyond 12 months in 20.7% (95% CI, 14.2-29.2). No independent variable reached statistical significance; the adjusted R-squared was 0.015 and remained unchanged across three sensitivity analyses. Patient and disease factors explained only 1.5% of the variance, and isolation-room capacity was not limiting. The key takeaway is that reducing the interval for patients beyond the guideline window requires review of service processes rather than finer risk stratification.
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