Abstract
Purpose To evaluate the role of 2-[18F]FDGPET/CT in the follow-up of radioiodine refractory thyroid cancer (RR-TC). Methods Forty-six 2-[18F]FDGPET/CT scans from 14 RR-TC patients were considered. Thyroid function tests: thyroglobulin (Tg), levothyroxine (LT4), and tyrosine-kinases inhibitors (TKIs) assumptions were recorded. Metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were calculated from each scan and correlated with clinical parameters and the overall survival (OS). Results Baseline TLG and MTV predicted OS (p = 0.027 and p = 0.035), and negative correlation with OS was also confirmed when the same parameters were measured in follow-up scans (p = 0.015 and p = 0.021). Tg also correlated with the OS; (p = 0.014; p = 0.019 and p = 0.009). However, TLG and MTV were not significantly correlated with Tg levels. MTV and TLG variation in time were reduced during TKI therapy (p = 0.045 and p = 0.013). Conclusions 2-[18F]FDGPET/CT confirmed its prognostic role at the first assessment and during the follow-up of RR-TC patients. 2-[18F]FDGPET/CT parameters seem at least partially independent from Tg. TKI therapy resulted in a measurable effect on the variation of 2-[18F]FDGPET/CT parameters over time.
Highlights
Advanced or metastatic radioiodine-refractory thyroid cancer (RR-TC) is a rare entity and its definition is still evolving [1]
Computed tomography (CT) scan represents the gold standard imaging technique both at the time of therapy initiation and during the follow-up [2,3,4,5], and tumour shrinkage assessed through RECIST 1.1 criteria is considered to measure the response to tyrosine-kinases inhibitors (TKIs) [11]
Out of 684 patients followed between 2009 and 2019, 46 2-[18F]FDGPET/CT scans were collected from 14 patients
Summary
Advanced or metastatic radioiodine-refractory thyroid cancer (RR-TC) is a rare entity and its definition is still evolving [1]. RR-TC is defined as a follicular-cell derived thyroid cancer no longer able to trap radioiodine or showing preserved radioiodine avidity only in some sites, or even displaying progression despite 131I treatments [1,2]. The efficacy of TKIs has to be balanced with their side effects, which could lead to dose reductions or even temporary or permanent drug discontinuation in a significant number of patients [9,10]. On this basis, effective follow-up strategies and imaging techniques are needed in order to assess progression, response rate, and duration, and to better define patients’ management. Computed tomography (CT) scan represents the gold standard imaging technique both at the time of therapy initiation and during the follow-up [2,3,4,5], and tumour shrinkage assessed through RECIST 1.1 criteria is considered to measure the response to TKIs [11]
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