Utility of ¹¹C-choline imaging as a supplement to F-18 FDG PET imaging for detection of thyroid carcinoma

Médecine nucléaire et cancers de la thyroïde en 2024 : iode 131, TEP et nouvelles approches théranostiques

NUCLEAR MEDICINE AND THYROID CANCERS IN 2024: IODINE 131, PET AND NEW THERANOSTIC APPROACHES: Nuclear medicine has long been a mainstay in the management of thyroid cancers. In patients with differentiated thyroid cancer (DTC), the most common histotype, radioiodine (RAI, 131I) has been for years a cornerstone for the treatment of RAI-avid metastases. Post-therapeutic 131I scintigraphy helps guide these treatments and contributes to the definition of refractory cancers. In these refractory patients, who represent fewer than 5% of CTDs, 18FDG PET plays a central diagnostic and prognostic role. From a therapeutic perspective, RAI uptake can be re-induced in some of these patients with the BRAF mutation by using redifferentiation protocols. In anaplastic thyroid cancer (A TC) that is rare, aggressive and undifferentiated, 18FDG PET remains the metabolic imaging of choice. In medullary thyroid cancer (MTC), PET imaging is mainly based on the use of 18F-DOPA, even if 18FDG also provides prognostic data and 68Ga-DOTATOC could allow a theranostic approach. Other radiopharmaceuticals offering new theranostic avenues in thyroid cancers are also discussed, such as prostate-specific membrane antigen (PSMA) and fibroblast activation protein (FAP). After decades of a "one-size fits all" approach in thyroid cancer management, molecular imaging is paving the way towards personalized medicine.

18F-Fluorocholine Positron Emission Tomography/Computed Tomography is a Highly Sensitive but Poorly Specific Tool for Identifying Malignancy in Thyroid Nodules with Indeterminate Cytology: The Chocolate Study

Background: Refining the risk of malignancy in patients presenting with thyroid nodules with indeterminate cytology (IC) is a critical challenge. We investigated the performances of ¹⁸F-fluorocholine (FCH) positron emission tomography/computed tomography (PET/CT) to predict malignancy. Methods: Between May 2016 and March 2019, 107 patients presenting with a thyroid nodule ≥15 mm with IC and eligible for surgery were included in this prospective study. Head-and-neck PET/CT acquisitions were performed 20 and 60 minutes after injection of 1.5 MBq/kg of FCH. PET/CT acquisition was scored positive when maximal standardized uptake value in the IC nodule was higher than in the thyroid background. Pathology was the gold standard for diagnosis. Results: At pathology, 19 (18%) nodules were malignant, 87 were benign, and one was a noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). Sensitivity, specificity, accuracy, positive-predictive value (PPV), and negative-predictive value (NPV) of FCH PET/CT in detecting cancer or NIFTP were 90%, 50%, 55%, 29%, and 96% at 20 minutes and 85%, 49%, 67%, 28%, and 94% at 60 minutes, respectively. Higher specificity (58% vs. 33%, p = 0.01) was observed in nononcocytic (n = 72) than in oncocytic IC nodules (n = 35). The pre-PET/CT probability of cancer or NIFTP in Bethesda III-IV nodules was 11% and the post-PET/CT probability was 19% in PET-positives and 0% in PET-negatives. In retrospective analysis, 42% of surgeries would have been unnecessary after PET/CT and 81% before (p < 0.001), resulting in a hypothetical 48% reduction (95% confidence interval [32-64]). Conclusions: FCH PET/CT offers high NPV to reliably exclude cancer in PET-negative IC nodules, but suffers from low PPV, particularly in those with oncocytic cytology. ClinicalTrials.gov identifier: NCT02784223.

Identification of Radioactive Iodine Refractory Differentiated Thyroid Cancer

Most differentiated thyroid cancer (DTC) patients have an excellent prognosis. However, about one-third of DTC patients with recurrent or metastatic disease lose the hallmark of specific iodine uptake initially or gradually and acquire radioactive iodine-refractory DTC (RAIR-DTC) with poor prognosis. Due to the potentially severe complications from unnecessarily repeated RAI therapy and encouraging progress of multiple targeted drugs for advanced RAIR-DTC patients, it has become crucial to identify RAIR-DTC early. In this review, we focus on the progress and controversies regarding the defining of RAIR-DTC, further with subsistent approaches and promising molecular nuclear medicine imaging in identifying RAIR-DTC, which may shed light on the proper management methodsof such patients.

F18-choline/C11-choline PET/CT thyroid incidentalomas

INTRODUCTION

Thyroid incidentaloma is defined as a thyroid lesion incidentally and newly detected by imaging techniques performed for an unrelated purpose and especially for a non-thyroid disease. Aim of this review is to evaluate the prevalence and clinical significance of focal incidental radiolabelled choline uptake in the thyroid gland (CTI) revealed by PET or PET/CT.

METHODS

A comprehensive computer literature search of the PubMed/MEDLINE, Scopus, and Embase databases was conducted to find relevant published articles about the prevalence and clinical significance of CTIs detected by PET or PET/CT in patients studied for other oncologic purposes.

RESULTS

Fifteen articles (14 case reports, one retrospective study on a larger population sample) were included in the systematic review. Considering the case reports, 7/14 CTIs were benign and 7/14 malignant. In the retrospective study on a larger population sample, 14/15 CTIs which underwent further investigations were benign.

CONCLUSION

Despite very rare but probably underestimated, CTIs frequently signal in the presence of unexpected lesions in the thyroid that differ from the indicated reason for which the patient was initially scanned, and the risk of malignancy is not negligible.

Role of 18F-Choline Positron Emission Tomography/Computed Tomography to Detect Structural Relapse in High-Risk Differentiated Thyroid Cancer Patients

BACKGROUND

This study aimed to evaluate the role of ¹⁸F-choline (¹⁸F-FCH) positron emission tomography (PET)/computed tomography (CT) in high-risk differentiated thyroid cancer (DTC) patients with suspected relapse. It also compared ¹⁸F-FCH-PET/CT results with those of fludeoxyglucose (¹⁸F-FDG)-PET/CT and evaluated the additional diagnostic value and clinical impact of the combined use of these two tracers. Finally, it assessed the association between the clinical, biochemical, and histological parameters and ¹⁸F-FCH-PET/CT and ¹⁸F-FDG-PET/CT results.

METHODS

The study prospectively enrolled high-risk DTC patients treated with thyroidectomy and radioactive iodine therapy and presenting high/increasing thyroglobulin levels under thyrotropin suppression, negative/inconclusive neck ultrasound, and negative ¹³¹I whole-body scan. All patients underwent ¹⁸F-FDG-PET/CT and ¹⁸F-FCH-PET/CT within 30 days of each other. Experienced nuclear medicine physicians examined the images of both procedures, and an integrated analysis of the two PET/CT modalities was also conducted. For each modality, a patient-based analysis (PBA) and lesion-based-analysis (LBA) was performed. On PBA, sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were calculated. On LBA, only sensitivity was calculated. The standard of reference was based on clinical, imaging, and histological data.

RESULTS

Twenty-five high-risk DTC patients were included; DTC relapse/persistence was confirmed in 23 patients. On PBA, ¹⁸F-FDG-PET/CT, ¹⁸F-FCH-PET/CT, and the integrated evaluation of the two imaging modalities showed the following rates: sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were 69.6%, 100%, 22.2%, 100%, and 72% versus 56.5%, 100%, 16.7%, 100%, and 60% versus 82.6%, 100%, 33.3%, 100%, and 84%, respectively. When compared with ¹⁸F-FDG-PET/CT, the integrated analysis of these two imaging procedures changed the clinical management in 4/23 (17%) patients. On LBA, the sensitivity rates of ¹⁸F-FDG-PET/CT, ¹⁸F-FCH-PET/CT, and the combined evaluation of the two modalities were 58.7%, 38.1%, and 66.7%, respectively; when only lymph node involvement was considered, the rates were 56.3%, 53.1%, and 68.8%, respectively. Serum thyroglobulin doubling time (Tg-DT) <12 months was significantly associated with positive 18F-FCH-PET/CT. A trend toward a significant association was also found between positive 18F-FDG-PET/CT and both Tg-DT <12 months and DTC aggressive subtypes.

CONCLUSION

¹⁸F-FCH-PET/CT may add important information during the follow-up of high-risk DTC patients. ¹⁸F-FCH-PET/CT may be considered a useful complementary tool in patients affected by non-aggressive DTC subtypes, with Tg-DT <12 months, high risk of lymph node spreading, and negative or doubtful ¹⁸F-FDG-PET/CT.

PET/CT in thyroid nodule and differentiated thyroid cancer patients. The evidence-based state of the art

A more conservative approach to the clinical management of thyroid nodules and differentiated thyroid cancer has recently been proposed by the 2015 ATA guidelines. In this context, fine-needle aspiration biopsy has been reserved for nodules with particular ultrasound features or dimensions that exclude low-risk thyroid lesions. Accordingly, a less aggressive surgical approach (i.e. lobectomy) has been recommended as the first-choice treatment in nodules with indeterminate cytology or in small cytologically confirmed malignant nodules. At the same time, radioactive remnant ablation has been considered only for DTC patients with concrete risks of disease persistence/relapse after thyroidectomy. In addition, further radioactive iodine therapies (RAI) have been proposed only for patients presenting unresectable and iodine-avid structural relapse. In this complex scenario, which requires attention to each clinical aspect of the patient, the introduction of accurate diagnostic tools is highly warranted. PET/CT is a very sensitive and specific diagnostic procedure that can better characterize the risk of thyroid nodules, identify DTC relapse early and predict the response to RAI. Thus, it seems essential to customize a more conservative approach to thyroid nodules and DTC patients. The aim of this review is to report the principal clinical context in which PET/CT has been used and to evaluate the evidence-based support for each diagnostic indication.

18F-choline PET/CT incidental thyroid uptake in patients studied for prostate cancer

PURPOSE

Thyroid incidental uptake is defined as a thyroid uptake incidentally detected by imaging examinations performed for non-thyroid disease. The aim of this study was to establish the prevalence and the pathological nature of focal thyroid incidental uptake (FTIU) among patients studied with 18F-choline-PET/CT.

MATERIALS AND METHODS

We retrospectively evaluated 368 patients who performed 18F-choline-PET/CT between June 2016 and August 2018. The PET images were analyzed visually and semi-quantitatively by measuring the maximum standardized uptake value (SUVmax) and the mean SUV (SUVmean) of the thyroid gland and of the FTIU; every focal thyroid uptake deviating from physiological distribution and background was considered FTIU. Final diagnosis of FTIU was obtained by cytological or histological examination after surgery.

RESULTS

The average SUVmax and SUVmean of thyroid gland in population were 3 and 1.8. Among 368 patients, FTIU was identified in nine cases (2.4%) and eight underwent further investigations to determine the nature. Two FTIU were classified as malignant (thyroid carcinoma), whereas five were benign (three nodular hyperplasia, one follicular adenoma, one Hurtle cell adenoma) and one indeterminate at cytological examination. In malignant lesions, average SUVmax was 9.6 and 4.5, respectively, while average SUVmean was 5.3 and 2.9, respectively. Average SUVmax and SUVmean of benign lesions were 4.9 and 3.2 and of the indeterminate lesion 5 and 3, respectively.

CONCLUSIONS

18F-choline-PET/CT FTIU may be a relevant diagnostic reality, which requires further investigations and affects management, especially considering that, despite being mainly benign, also malignancy is possible.

Incidental Finding of Intrathyroid Metastases of Prostatic Cancer on 18F-Choline PET/CT

An 85-year-old man with a 2-year history of prostate cancer, treated with radiotherapy and hormonal therapy, presented increased prostatic-specific antigen levels. F-choline PET/CT showed focal prostatic uptake consistent with known local recurrence, increased uptake of 2 hypodense thyroid nodules and of 2 left cervical lymph nodes, suspected as thyroid cancer. Neck ultrasound confirmed the high risk of malignancy, and a guided biopsy (of a thyroid nodule and cervical lymph node) revealed cellular infiltrates thyroid transcription factor-1 (TTF-1) negative and prostatic-specific antigen positive, confirming intrathyroid and cervical lymph node metastases of prostate cancer. PET/CT changed the disease staging. Chemotherapy was initiated.

Follicular thyroid cancer avid on C-11 Methionine PET/CT

A case of follicular thyroid cancer with intense focal Methionine uptake on 11C-Methionine PET/CT is reported here. The use of 11C-Methionine PET in differentiated thyroid cancer is currently being investigated as a surrogate tracer compared to the more widely used 18F-FDG PET. This case illustrates the potential incremental value of this modality, not only in the localizing of parathyroid adenoma, but also indicating that 11C-Methionine PET might have a potential of increasing the pretest likelihood of thyroid malignancy in a cold nodule with highly increased Sestamibi uptake.

Incidental Detection of Occult Thyroid Carcinoma with 11C-Choline PET/CT for High Risk Prostate Cancer

We report a case of a 65-year-old male patient with high-risk prostate cancer, re-staged with ¹¹C-choline positron emission tomography/computed tomography (PET/CT) for prostate specific antigen recurrences 3 years after radical prostatectomy and adjuvant radiation therapy. In addition to 2 suspicious presacral lymph nodes which were resected and proven to be metastatic, PET/CT revealed a very high uptake in a calcified thyroid nodule. Evaluation with fine needle aspiration was suspicious for thyroid carcinoma and the patient underwent total thyroidectomy, confirming a non-metastatic encapsulated follicular variant of papillary thyroid carcinoma. To our knowledge, this is the first report of a thyroid cancer diagnosed with ¹¹C-choline PET/CT for prostate cancer staging.

Dual Pathologies of Parathyroid Adenoma and Papillary Thyroid Cancer on Fluorocholine and Fluorodeoxyglucose PET/CT

¹⁸F-Fluorocholine (FCH) PET/CT is evolving as a functional imaging modality for the preoperative imaging of abnormal parathyroid tissue(s) helping to localize eutopic and ectopic parathyroid tissue and limit the extent of surgery. FCH PET/CT may show incidental uptake in various thyroid lesions necessitating further evaluation, whereas the role of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT in the detection of incidental thyroid nodules is well documented. The case of a middle-aged woman with dual pathology of parathyroid adenoma and papillary thyroid cancer detected on FCH and FDG PET/CT is presented.

Incidental Detection of Oxyphilic Papillary Thyroid Carcinoma by 18F-Fluorocholine PET/CT

A 70-year-old man with prostate cancer and increased prostate-specific antigen level of 55 ng/mL underwent staging F-fluorocholine PET/CT, which demonstrated the primary prostate tumor and a focal area corresponding to a 2-cm hypodense nodule in the left thyroid lobe. Fine-needle aspiration and subsequent total thyroidectomy with central lymph node dissection showed an oxyphilic papillary thyroid carcinoma and a medullary microcarcinoma. Oxyphilic tumors represent a significant proportion of the few case reports of incidental focal thyroid fluorocholine thyroid uptake.

¹¹C-Choline PET/CT in Recurrent Prostate Cancer and Nonprostatic Neoplastic Processes

Choline positron emission tomography (PET)/computed tomography (CT), with both carbon 11 ((11)C) choline and fluorine 18 ((18)F) choline, is an increasingly used tool in the evaluation of patients with biochemically recurrent prostate cancer. It has allowed detection and localization of locally recurrent and metastatic lesions that were difficult or impossible to identify using more conventional modalities. Many of the patients followed for their prostate cancer are elderly and have a higher rate of nonprostate cancer lesions or malignancies. As our experience with choline PET/CT has grown, it has become apparent that many of these nonprostate cancer processes, both benign and malignant, can be detected. Invasive thymoma, renal cell carcinoma, papillary thyroid carcinoma, and parathyroid adenoma are a few of the processes that have been incidentally detected with (11)C-choline PET/CT at our institution and have significantly altered subsequent clinical management of the patient. Although most of the secondary lesions are detected due to their increased (11)C-choline avidity, several have been detected due to their decreased or lack of avidity in the background of a highly avid organ. For instance, large liver masses that are relatively non-choline-avid create large activity defects in the otherwise highly active liver. Familiarity with normal (11)C-choline physiologic activity, the most common prostate metastatic patterns, and imaging characteristics of secondary lesions is essential for the detection and correct diagnosis of such lesions so that proper follow-up and management can be recommended.

Lymph Node Metastasis from Tall-Cell Thyroid Cancer Negative on 18F-FDG PET/CT and Detected by 18F-Choline PET/CT

A 77-year-old woman underwent thyroidectomy and (131)I remnant ablation for tall-cell differentiated cancer (DTC) of the left lobe. Detectable Tg levels (4.1 μg/L) under TSH suppression, with undetectable serum Tg-antibody levels, prompted neck ultrasonography, which revealed a lymph node in the left laterocervical region and in the right retroclavicular region. (18)F-FDG PET/CT showed uptake by the left lymph node. (18)F-choline PET/CT showed increased uptake by both lymph nodes. Histopathology revealed DTC solid metastasis in the left lymph node and solid and cystic metastasis in the right one. (18)F-choline PET/CT can locate virulent DTC recurrence, thereby increasing (18)F-FDG PET/CT information.

Incidental uptake of (18)F-fluorocholine (FCH) in the head or in the neck of patients with prostate cancer

Background

Positron emission tomography-computed tomography (PET/CT) with ¹⁸F-fluorocholine (FCH) is routinely performed in patients with prostate cancer. In this clinical context, foci of FCH uptake in the head or in the neck were considered as incidentalomas, except for those suggestive of multiple bone metastases.

Results

In 8 patients the incidental focus corresponded to a benign tumour. The standard of truth was histology in two cases, correlative imaging with MRI in four cases, ^99mTc-SestaMIBI scintigraphy, ultrasonography and biochemistry in one case and biochemistry including PTH assay in one case. The final diagnosis of benign tumours consisted in 3 pituitary adenomas, 2 meningiomas, 2 hyperfunctioning parathyroid glands and 1 thyroid adenoma.

Malignancy was proven histologically in 2 other patients: 1 papillary carcinoma of the thyroid and 1 cerebellar metastasis.

Conclusions

To the best of our knowledge, FCH uptake by pituitary adenomas or hyperfunctioning parathyroid glands has never been described previously. We thus discuss whether there might be a future indication for FCH PET/CT when one such tumour is already known or suspected: to detect a residual or recurrent pituitary adenoma after surgery, to guide surgery or radiotherapy of a meningioma or to localise a hyperfunctioning parathyroid gland. In these potential indications, comparative studies with reference PET tracers or with ^99mTc-sestaMIBI in case of hyperparathyroidism could be undertaken.

Preliminary study on the evaluation of olfactory neuroblastoma using PET/CT

PURPOSE

Because of paucity of data available regarding the utility of PET/CT in the diagnosis and staging of patients with olfactory neuroblastoma (ONB), we retrospectively analyzed the efficacy of PET/CT in 9 patients with ONB.

MATERIALS AND METHODS

Whole-body F-18 FDG PET/CT was performed in 7 patients with newly diagnosed ONB, as well as in 1 patient with recurrence and in 1 patient with remnant tumor. Regional C-11 choline (C-11 CHO) PET/CT was performed in 2 patients with negative F-18 FDG scans. The lesion with intense radiotracer uptake was suggested as positive for tumor and the results of PET/CT were compared with conventional staging examinations.

RESULTS

F-18 FDG PET/CT was positive in 7/9 (77.7%) patients with ONB. In 2 patients with negative F-18 FDG, the lesions were C-11CHO avid. Both the primary tumors and its invasions were clearly delineated by F-18 FDG or C-11 CHO PET/CT. SUVmax of F-18 FDG in the primary tumor was 6.37 ± 4.22 and did not correlate with lesion size (F-18 FDG/size: r = 0.097, P = 0.820). Whole-body F-18 FDG PET/CT detected parapharyngeal and cervical lymph node metastases in 2 patients, lung metastases in 1 patient, liver metastases in 1 patients, and bone metastases in 2 patients. PET/CT altered the stages of 3 of 9 patients with upstaging in 2 patients and downstaging in 1 patient.

CONCLUSIONS

PET/CT may be useful for the diagnosis and staging of ONB.