Photo Credit: Dr. Microbe

The following is a summary of “Correlation between remnant thyroid gland I-131 uptake and serum thyroglobulin levels: can we rely on I-131 whole body scans?,” published in the January 2024 issue of Oncology by Hwang et al.

In the realm of I-131 treatment (RAI) decision-making for papillary thyroid cancer, serum thyroglobulin (Tg) levels have traditionally played a pivotal role, as their elevation is conventionally linked to heightened I-131 uptake. The contemporary clinical landscape increasingly recognizes the relevance of Tg elevation, and negative iodine scintigraphy (TENIS), particularly as alternative therapeutic approaches gain prominence. This retrospective study spanning from March 2012 to July 2019 delves into the intricate correlation between Tg levels and I-131 uptake in the remnant thyroid gland, shedding light on the dependability of serum Tg levels as a predictive marker for I-131 uptake. Involving 281 patients subjected to 150 mCi RAI, the investigation employed Early (2nd day) and Delayed (7th day) post-RAI whole-body scan (WBS) neck counts, aligning them with clinical and pathologic parameters. 

Notably, patients showcasing normal neck ultrasound, undetectable serum Tg (< 0.2 ng/mL), and thyroglobulin antibody (TgAb) (< 10 IU/mL) levels within 2 years post I-131 ablation were deemed as achieving ablation success. The study identified thyroid gland weight, tumor size, and the presence of thyroiditis as independent determinants of preoperative serum Tg levels. The correlation between serum off-Tg levels and Early and Delayed WBS neck counts was established, with thyroiditis pathology contributing to lower counts in both phases of WBS. Multivariable analysis revealed Delayed WBS neck count, serum off-Tg, and off-TgAb as significant factors in predicting ablation success. The findings underscore the correlation between I-131 uptake and remnant thyroid gland retention with serum off-Tg levels, thyroiditis, and ablation success. 

Moreover, the application of semi-quantitative I-131 analysis through Early and Delayed WBSs emerges as a valuable adjunct for evaluating ablation success, with potential implications for assessing treatment response in metastasis.

Source: cancerimagingjournal.biomedcentral.com/articles/10.1186/s40644-024-00664-0