The role of 201Tl scintigraphy in evaluating proliferative activity in thyroid neoplasms

To identify the relationship between the uptake of 201Tl and the proliferative activity in thyroid neoplasms, 201Tl scintigraphy was performed in 57 patients with thyroid neoplasms. 201Tl uptake ratio was calculated in both the early and the delayed images and then compared with factors representing cellular or practical proliferative activity of the lesions. The labeling index (LI) for proliferating cell nuclear antigen (PCNA) was determined quantitatively by flow cytometry. There was a significant correlation between the uptake ratio and LI for PCNA. The correlation coefficient for the delayed ratio (DR) vs. LI was better than that for the early ratio (ER) vs. LI. As parameters for practical proliferation, the surgical stage in primary thyroid carcinoma or 131I uptake in recurrent thyroid carcinoma was focused on. DR was strongly related to these parameters, regardless of the histopathological features or size of the lesions. Our results suggest that 201Tl uptake in delayed thyroid scan is useful in assessing proliferative activity in thyroid neoplasms.