Abstract
Objective
In this study, the response to treatment in patients with extra-thyroid extension
(ETE) of papillary thyroid cancer (PTC) was compared between different radioiodine
treatment doses.
Methods and Materials
In this retrospective cross-sectional study, patients with pathology-proven ETE who
were hospitalized for radioiodine therapy from December 2015 to May 2018 at a referral
university hospital were identified. Demographic data, radioiodine doses, and off-levothyroxine
thyroglobulin and antithyroglobulin levels, before and after treatment, were collected.
Alterations in thyroglobulin levels before and after treatment were compared between
patients receiving different doses of radioiodine.
Results
Sixty patients were analyzed (mean age: 44.1 ± 14.4 years; 61.7% females). On average,
the thyroglobulin levels were 59.1 ± 92.0 and 45.7 ± 81.5 ng/mL at baseline and after
treatment, respectively. The thyroglobulin levels decreased from 6.2 ± 6.3 to 1.7 ± 0.2 ng/mL
(p = 0.510), 55.8 ± 101.3 to 11.5 ± 17.2 ng/mL (p = 0.07), and 62.8 ± 91 to 60.9 ± 93.1 ng/mL (p = 0.83) in the 100- to 149-, 150- to 199-, and 200- to 250-mCi iodine therapy groups,
respectively. Treatment with doses of less than 200 mCi were significantly more effective
in reducing posttreatment thyroglobulin levels compared with higher doses (p = 0.05). In the subgroup analysis, nonmetastatic cases treated with less than 200
mCi iodine had significantly greater thyroglobulin reduction compared with metastatic
patients treated with ≥200 mCi iodine (p = 0.05). Macroscopic (vs. microscopic) invasion into adjacent tissues had no impact
on thyroglobulin decrease.
Conclusion
The administration of higher radioiodine doses for the treatment of PTC patients with
ETE does not yield additional therapeutic benefits in terms of posttreatment thyroglobulin
reduction.
Keywords extra-thyroid extension - PTC - radioiodine - therapeutic - thyroglobulin
