Abstract
Simple SummaryThe most advanced positron emission tomography–magnetic resonance (PET/MR) combines the high soft tissue contrast of MRI with the high functional/metabolic sensitivity of PET and has the potential to achieve the highest level of diagnostic performance for refractory malignancies in differentiated thyroid cancer (DTC) patients. The utility of PET/MR in the postoperative follow-up of DTC patients has been relatively ambiguous. This retrospective study compared 18F-fluorodeoxyglucose neck PET/MR with PET/CT head-to-head, in order to evaluate the diagnostic efficacy of PET/MR in assessment malignancy in DTC patients after comprehensive treatment. We determined that PET/MR presented better detection rates, image conspicuity, and sensitivity than PET/CT in recurrent DTC lesions and cervical lymph node metastases. The addition of neck PET/MR scan after whole-body PET/CT may provide more favorable diagnostic information.We explored the clinical value of 18F-FDG PET/MR in a head-to-head comparison with PET/CT in loco-regional recurrent and metastatic cervical lymph nodes of differentiated thyroid carcinoma (DTC) patients after comprehensive treatment. 18F-FDG PET/CT and neck PET/MR scans that were performed in DTC patients with suspected recurrence or cervical lymph node metastasis after comprehensive treatment were retrospectively analyzed. Detection rates, diagnostic efficacy, image conspicuity, and measured parameters were compared between 18F-FDG PET/CT and PET/MR. The gold standard was histopathological diagnosis or clinical and imaging follow-up results for more than 6 months. Among the 37 patients enrolled, no suspicious signs of tumor were found in 10 patients, 24 patients had lymph node metastasis, and 3 patients had both recurrence and lymph node metastases. A total of 130 lesions were analyzed, including 3 malignant and 6 benign thyroid nodules, as well as 74 malignant and 47 benign cervical lymph nodes. Compared with PET/CT, PET/MR presented better detection rates (91.5% vs. 80.8%), image conspicuity (2.74 ± 0.60 vs. 1.9 ± 0.50, p < 0.001, especially in complex level II), and sensitivity (80.5% vs. 61.0%). SUVmax differed in benign and malignant lymph nodes in both imaging modalities (p < 0.05). For the same lesion, the SUVmax, SUVmean, and diameters measured by PET/MR and PET/CT were consistent and had significant correlation. In conclusion, compared with 18F-FDG PET/CT, PET/MR was more accurate in determining recurrent and metastatic lesions, both from a patient-based and from a lesion-based perspective. Adding local PET/MR after whole-body PET/CT may be recommended to provide more precise diagnostic information and scope of surgical resection without additional ionizing radiation. Further scaling-up prospective studies and economic benefit analysis are expected.
Highlights
Thyroid carcinoma is the most common endocrine malignant tumor worldwide, accounting for 2% of all cancers, after a two-fold increase over the last 25 years [1,2,3]
We retrospectively reviewed the images of differentiated thyroid carcinoma (DTC) patients who underwent 18 F-FDG PET
Positive serum Tg and negative 131 I-WBS, (2) rising anti-thyroglobulin antibodies (TgAb) after radioactive iodine ablation, (3) suspected widespread metastases throughout the body, Cancers 2021, 13, 3436 eligible for 18 F-FDG PET examination according to the available guidelines at that time; (4) patients accepted 18 F-FDG PET/CT and subsequent PET/MR examination; (5) patients were available for follow-up including postoperative pathology/fine-needle aspiration biopsy (FNAB) or regular ultrasonography and Tg/TgAb level monitor every 3–6 months
Summary
Thyroid carcinoma is the most common endocrine malignant tumor worldwide, accounting for 2% of all cancers, after a two-fold increase over the last 25 years [1,2,3]. More than 90% of thyroid carcinomas are differentiated thyroid carcinoma (DTC), which includes papillary carcinoma (PTC) (85%) and follicular carcinoma (FTC) (12%). The prognosis of DTC is generally favorable after comprehensive treatment including surgery, radioactive iodine, and thyroid-stimulating hormone (TSH) suppression [4]. Of patients may experience local recurrence and/or metastasis within several decades, which indicates a poor prognosis and a drop of the five-year survival rate from higher than. Postoperative recurrence appears most frequently (60–75%) in cervical lymph nodes (LNs) [7]. Strict postoperative follow-up and advances in early detection are essential for a timely intervention in case of relapse and metastatic disease
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