Factors influencing radioiodine uptake after thyroid cancer surgery

Total thyroidectomy followed by radioactive iodine (RAI) ablation is indicated for most patients with differentiated thyroid cancer. There have been no quantitative studies testing factors that affect uptake on post-ablation whole body scan. We hypothesized greater RAI uptake in patients who underwent two-stage total thyroidectomy (diagnostic hemithyroidectomy followed by completion thyroidectomy) compared to patients who underwent one-stage total thyroidectomy.

Medical records and whole body scan images of thyroid cancer patients were reviewed. Thyroid uptake as a percentage of Iodine-131 dose was calculated for each scan. RAI uptake was compared to procedure type, central lymph node dissection (CLND), extrathyroidal invasion, presence of thyroiditis and pre-operative diagnosis.

One hundred six patients who underwent total thyroidectomy and RAI ablation for differentiated thyroid cancer were included. There was a trend to higher RAI uptake in patients who had undergone two-stage thyroidectomy compared to one-stage thyroidectomy (P = 0.06). CLND was associated significantly lower RAI uptake (P = 0.003). On multivariate analyses, CLND was the only variable that retained statistical significance (P = 0.023). CLND was performed more often in patients undergoing one-stage thyroidectomy (P = 0.001), as these patients' cancer diagnosis was known prior to surgery.

RAI uptake appeared higher in two-stage thyroidectomy than one-stage thyroidectomy. This difference may be attributed to CLND being performed more often in one-stage thyroidectomy. These results add to the discussion about the role of CLND in surgery for differentiated thyroid cancer.