We read with great interest the by paper by Christiane Gomes-Lima and colleagues, titled “Metastatic Differentiated Thyroid Cancer Survival Is Unaffected by Mode of Preparation for 131I Administration” [1].
The study describes 55 patients with metastatic differentiated thyroid carcinoma (DTC) who were treated with radioactive iodine (RAI) and compares the outcomes of patients prepared solely with recombinant human thyrotropin (rhTSH) or with thyroid hormone withdrawal (THW). The authors conclude that the mode of preparation for RAI therapy does not decisively affect the outcome of RAI therapy of patients with metastatic DTC [1].
As preparation with rhTSH is associated with an improvement of quality of life during RAI treatment [2], it is of great importance to study which patients with DTC can be treated with rhTSH without negatively effecting the cancer-specific outcomes. For patients with low- and intermediate risk DTC multiple studies have been conducted, including randomized controlled trials with a non-inferiority design, and eventually a in systematic review with more than 1500 patients, a pooled-analysis demonstrated a similar outcome in patients prepared with rhTSH and THW [3].
Patients with metastatic DTC in general have a survival of years and the aim of the treatment is to balance between quality and length of life. Besides the treatment with RAI also other therapeutic strategies such as surgery, radiotherapy, and multikinase inhibitors are of value to reach this goal [4]. Nowadays, the (dis) advantages of these approaches have to be discussed with the patient to finally achieve a shared decision. The advantages of rhTSH are clearly described in this paper; however, the long-term outcome remains uncertain.
Studies like the current one by Gomes-Lima and colleagues are highly needed to optimize the palliative treatment in metastatic DTC. However, the methods and results of this study have certain limitations that need additional comment; in our opinion, the results of the study do not conclude equality between preparation with rhTSH or THW. Considering the relative long survival of patients with metastatic DTC, the current study will probably be underpowered and the follow-up too short to detect any difference in overall survival. With regard to progression-free survival, the current study found a hazard ratio of 0.48 (95% CI, 0.18-1.26) for THW vs preparation with rhTSH after correcting for age, macronodular lung metastases, number of therapies, and cumulative 131I dose. These results might suggest that in a larger cohort perhaps the progression-free survival of the THW group would have been significantly longer, but probably this difference is caused by residual confounding. Still, the lack of a statistically significant difference does not mean equality. Therefore, the conclusion by the authors that “the mode of preparation for RAI therapy does not decisively affect the outcome of RAI therapy of patients with metastatic DTC” (sic) is not supported by the results of the current study and therefore the title of this paper does not cover the content. We do agree that larger studies with a non-inferiority design are required to end the debate and it would be a great challenge to work internationally on this topic.
Abbreviations
- DTC
differentiated thyroid cancer
- RAI
radioactive iodine
- rhTSH
recombinant human thyrotropin (thyroid-stimulating hormone)
- THW
thyroid hormone withdrawal
Contributor Information
Wouter T Zandee, Email: w.t.zandee@umcg.nl, Department of Internal Medicine Division of Endocrinology, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands.
Thera P Links, Department of Internal Medicine Division of Endocrinology, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands.
Disclosure Statement
Both authors have nothing to disclose.
References
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