Outcomes of Thyrotropin Alfa Versus Levothyroxine Withdrawal-Aided Radioiodine Therapy for Distant Metastasis of Papillary Thyroid Cancer

Background: Thyrotropin alfa (rhTSH) is not currently approved by the Food and Drug Administration or European Medicines Agency for the preparation of radioactive iodine therapy (RAIT) in patients with distant metastatic papillary thyroid cancer (PTC). There are only a few studies comparing rhTSH with levothyroxine withdrawal (LTW) in this context. Our main aim was to compare the two methods of RAIT preparation in terms of avidity and structural/biochemical response in distant metastatic PTC. We also intended to evaluate whether the two methods of RAIT preparation represented independent prognostic factors for progression-free survival (PFS) and disease-specific survival (DSS) in this subset of patients. Methods: We performed a retrospective analysis of all patients with PTC treated with RAIT for distant metastatic disease between 2006 and 2018. We included 95 PTC patients-27 (28.4%) had LTW and 68 (71.6%) had rhTSH for RAIT. Results: The two groups presented similar clinicopathological characteristics, except for median age at PTC diagnosis, which was higher in the rhTSH group (p = 0.001), but the median age at first RAIT for distant metastatic disease was not different between the two methods of preparation, 63 years old (interquartile range [IQR] 23) in the LTW group versus 70 (IQR 26.75), p = 0.06. Avidity was similar between the two groups (p = 0.973). Median estimate PFS (p = 0.076) and DSS (p = 0.084) were also similar between LTW and rhTSH. Regarding RAIT-related side effects, only 1 (3.7%) patient and 5 (7.4%) patients in the LTW and rhTSH groups, respectively, reported sialadenitis (p = 0.670). Conclusions: There were no differences between the two methods of RAIT preparation regarding avidity and clinical response. rhTSH may be used as an alternative method of preparation for RAIT in patients with known distant lesions, as it presents similar clinical outcomes to LTW and a good safety profile.

Effect of recombinant human thyroid-stimulating hormone or levothyroxine withdrawal on salivary gland dysfunction after radioactive iodine administration for thyroid remnant ablation

BACKGROUND

The purpose of this study was to examine the incidence of sialadenitis and xerostomia within a year after radioactive iodine administration for thyroid remnant ablation after preparation with recombinant human thyroid-stimulating hormone (rhTSH) or levothyroxine (LT4 ) withdrawal.

METHODS

The study has included 121 patients, divided into 4 groups: group A (rhTSH = 100 mCi), group B (rhTSH = 70 mCi), group C (LT4 withdrawal = 100 mCi), and group D (LT4 withdrawal = 70 mCi). Study outcomes were Summated Xerostomia Inventory score and number of sialadenitis episodes after radioactive iodine administration.

RESULTS

Salivary gland dysfunction was reported in 31% and 12% of patients, at the end of months 1 and 12, respectively. There was significantly lower incidence in groups A and B in comparison with groups C and D (p = .002 and .021, respectively).

CONCLUSION

The use of rhTSH for preparation of radioactive iodine ablation as opposed to LT4 withdrawal reduces the incidence of salivary gland dysfunction. © 2015 Wiley Periodicals, Inc. Head Neck 38: E227-E230, 2016.