Comparison of 68Ga PET/CT to Other Imaging Studies in Medullary Thyroid Cancer: Superiority in Detecting Bone Metastases

Head-to-Head Comparison of 68Ga-FAPI-04 and 68Ga-DOTA-TATE PET/CT in Recurrent Medullary Thyroid Cancer

PURPOSE

We aimed to compare the diagnostic performance of 68Ga-FAPI-04 (FAPI) in comparison to 68Ga-DOTATATE (SSTR) PET/CT for patients presenting with recurrent medullary thyroid carcinoma (MTC).

PATIENTS AND METHODS

Sixteen MTC patients with elevated calcitonin levels (>150 pg/mL) underwent FAPI and SSTR PET/CT. Two nuclear medicine physicians evaluated all images, categorizing lesions into locoregional metastases, mediastinal lymph nodes (LNs), liver, and bone metastases. SUVmax and tumor-to-background ratio were recorded. PET modalities were compared using the McNemar test. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FAPI and SSTR PET were calculated.

RESULTS

The cohort comprised 16 patients (50% female; mean age 50 ± 17 years). Median calcitonin and CEA levels were 6234 pg/mL and 17.3 ng/mL, respectively. In patient-based analysis, SSTR exhibited higher diagnostic sensitivity compared with FAPI (88% vs 81%), resulting a statistically significant difference (P = 0.004). Mean SUVmax and tumor-to-background ratio values were 10.3 and 5.35 for FAPI, and 9.7 and 11.9 for SSTR PET, respectively. In lesion-based analyses, FAPI demonstrated higher accuracy than SSTR for cervical LNs (91.9% vs 50%), mediastinal LNs (94.9% vs 54.4%), and liver metastases (57.4% vs 7.3%), respectively. Notably, 31% of patients (n = 5) with FAP-expressing liver lesions showed no uptake on SSTR imaging. MRI confirmed liver metastases in 3 of these patients; however, 2 FAP-expressing lesions were confirmed as hemangiomas. False-positive findings of DOTA primarily included reactive LNs and bone hemangiomas.

CONCLUSIONS

FAPI PET presents promising outcomes in detecting metastases in recurrent MTC patients. Although its diagnostic performance matches SSTR on a per-patient basis, FAPI PET exhibits superior sensitivity and accuracy in lesion-based analyses, notably for liver and bone metastases.

Fundamentals and recent advances in the evaluation and management of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare primary neuroendocrine thyroid carcinoma that is distinct from other thyroid or neuroendocrine cancers. Most cases of MTC are sporadic, although MTC exhibits a high degree of heritability as part of the multiple endocrine neoplasia syndromes. REarranged during Transfection (RET) mutations are the primary oncogenic drivers and advances in molecular profiling have revealed that MTC is enriched in druggable alterations. Surgery at an early stage is the only chance for cure, but many patients present with or develop metastases. C-cell-specific calcitonin trajectory and structural doubling times are critical biomarkers to inform prognosis, extent of surgery, likelihood of residual disease, and need for additional therapy. Recent advances in the role of active surveillance, regionally directed therapies for localized disease, and systemic therapy with multi-kinase and RET-specific inhibitors for progressive/metastatic disease have significantly improved outcomes for patients with MTC.

The Clinical Utility of Gallium-68-DOTATATE Positron Emission Tomography Scanning in Medullary Thyroid Cancer

OBJECTIVE

Somatostatin receptor (SST) functional imaging with positron emission tomography (PET)/computed tomography (CT) has broadened the diagnostic and staging capabilities for medullary thyroid cancer (MTC). Gallium-68 (68Ga)-DOTA-conjugated peptide (Tyr3)-octreotate (DOTATATE) is a radiotracer with a high affinity for type 2 SSTs expressed in several, but not all, MTCs. The utility of 68Ga-DOTATATE PET/CT and 18fluorine-labeled fluoro-2-deoxy-D-glucose (18F-FDG)-PET/CT imaging in predicting MTC prognosis is also unknown.

METHODS

In this single-center retrospective study, 103 of patients with MTC underwent assessment of SST2 and SST5 immunohistochemistry (IHC). A subgroup of 37 patients received 68Ga-DOTATATE PET/CT imaging, and 13 received contemporaneous 18F-FDG-PET/CT imaging. The maximum standardized uptake value (SUV), mean SUV, metabolic tumor volume, and total lesion activity (TLA) were assessed.

RESULTS

Forty-two patients (41%) demonstrated positive expression of SST2, and 45 (44%) had a positive SST5 IHC result. Seventeen patients (17%) expressed both SST2 and SST5. No survival advantage was identified with SST2 or SST5 IHC positivity. No correlation was noted between the maximum SUV, mean SUV, metabolic tumor volume, or TLA and SST2 and/or SST5 expression by IHC. Shorter survival was associated with a TLA of >20 (P = .04). A RET-negative status also appeared to have shorter survival, although this may be because the small numbers did not reach statistical significance (P = .12).

CONCLUSION

Assessment of TLA from 68Ga-DOTATATE PET/CT may predict survival. SST2 IHC was not correlated with 68Ga-DOTATATE avidity. Metastatic disease may be optimally assessed by concurrent 18F-FDG and 68Ga-DOTATATE imaging.

Pancreas as an Unusual Metastatic Site of Medullary Thyroid Carcinoma: A Case of Very Long-term Follow-up Under Prolonged Treatment with Somatostatin Analogues

BACKGROUND

Pancreatic metastases from medullary thyroid carcinoma (MTC) are exceptional. Imaging and treatment based on somatostatin receptors may play a role, though the evidence is unconvincing.

CASE PRESENTATION

We have, herein, documented a unique case of metastatic MTC, where pancreatic metastasis was identified by 68Ga-PET/CT, with the disease showing very slow progression during treatment with lanreotide autogel. A 51-year-old woman underwent total thyroidectomy for goiter in 2000, with a postoperative diagnosis of MTC. Due to persistent disease, somatostatin analogues (SSA) treatment commenced in 2005, following a positive acute octreotide test. In 2012, a pathology-confirmed pancreatic metastasis was diagnosed via 68Gallium-positron emission tomography (68Ga-PET/CT). The disease progressed very slowly over 17 years of SSA treatment.

CONCLUSION

This uncommon case of pancreatic metastasis from MTC indicates that nuclear medicine techniques might offer valuable additional information. Extended treatment with lanreotide autogel appears to correlate with very slow disease progression in selected patients.

[Hereditary medullary thyroid cancer]

Parafollicular C cells progress via C cell hyperplasia to medullary thyroid cancer (MTC), which can be present even in the first years of life in multiple endocrine neoplasia (MEN) type 2A and 2B patients. Basal calcitonin and carcinoembryonic antigen (CEA) are useful tumor markers for the diagnosis and monitoring. The prognosis depends on the stage when the disease is diagnosed and there is a good genotype-phenotype correlation with the RET proto-oncogene, which can be used for estimation of the risk. The risk-stratified prophylactic thyroidectomy plays a decisive role in the prognosis of known gene mutation carriers.

Feasibility and therapeutic potential of the 68Ga/177Lu-DOTATATE theranostic pair in patients with metastatic medullary thyroid carcinoma

BACKGROUND

This study assessed: 1) the clinical efficacy of imaging with 68Ga-DOTATATE PET/CT (SSTR (somatostatin receptor)-PET) to detect medullary thyroid carcinoma (MTC); and 2) the therapeutic efficacy of peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTATATE in MTC patients.

MATERIALS AND METHODS

Patients with histologically proven MTC and suspected recurrence following thyroidectomy, based on raised serum calcitonin levels, underwent SSTR-PET. In addition, to evaluate the clinical efficacy and safety of PRRT, the patients with intense uptake on SSTR-PET or 99mTc-octreotide scintigraphy underwent PRRT. The Common Terminology Criteria for Adverse Events (version 4.03) was used to grade adverse events after PRRT. Treatment response was classified as complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD).

RESULTS

Twenty MTC patients (10 male, 10 female) with a median age of 48.5 years underwent SSTR-PET. SSTR-PET was positive in 17/20 patients (85%). Four of the 17 patients with positive SSTR-PET were scheduled for PRRT. In addition, 2 patients had positive 99mTc-octreotide scintigraphy results (Krenning score ≥ 2) and were scheduled for PRRT. Two of the 6 patients who underwent PRRT showed PR, 2 SD and 2 PD. Two patients died during the follow-up period. Median overall survival was 19 months (95% CI: 5.52-29.48). There were no cases of significant toxicity.

CONCLUSION

Radiolabeled somatostatin analogs are contributive for the management of recurrent MTC. 68Ga-DOTATAE PET-CT showed a relatively high detection rate in recurrent MTC. In addition, PRRT with 177Lu-DOTATATE was found to be a safe alternative therapeutic option for MTC.

Application of dual-source computed tomography in the diagnosis of thyroid cancer and evaluation of biological behaviors

OBJECTIVE

Thyroid cancer (TC) is an extremely prevailing malignant endocrine tumor. Therefore, effective diagnostic tools are necessary. This study explored the application value of dual-source computed tomography (DSCT) in TC diagnosis and biological behavior assessment.

METHODS

This study retrospectively selected 68 TC patients and another 74 benign patients with thyroid adenoma, nodular goiter, or adenomatous hyperplasia. All patients were confirmed by pathological examination and underwent DSCT examination. The iodine concentration (IC) obtained from plain computed tomography (CT) scanning and normalized iodine concentration (NIC) in the arterial phase and venous phase were recorded. The positive expression rates of estrogen receptor alpha (ERα), estrogen receptors beta (ERβ), and Ki67 in pathological tissues were determined by immunohistochemistry, and their correlation with IC in plain CT was assessed by Pearson correlation analysis, respectively. The diagnostic values of IC in plain CT and venous phase NIC in TC patients were evaluated using the receiver operating characteristic curve.

RESULTS

Malignant patients had lower IC in plain DSCT scanning, venous phase NIC, and ERβ, and higher ERα and Ki67 than benign patients. IC level in plain DSCT scanning was inversely-correlated with ERα and Ki-67 positive expression rates, but positively-related to ERβ to different degrees. For the diagnosis of TC patients, the AUC of IC level in plain DSCT was 0.771, with a cut-off value of 1.250 (97.06% sensitivity and 41.89% specificity), and the AUC of venous phase NIC was 0.738, with a cut-off value of 0.825 (100% sensitivity and 43.24% specificity).

CONCLUSION

The IC level obtained from DSCT scanning could assist in the differential diagnosis of malignant and benign thyroid nodules and evaluation of biological behaviors.

Update on the Diagnosis and Management of Medullary Thyroid Cancer: What Has Changed in Recent Years?

Medullary thyroid carcinoma (MTC) is a neoplasm originating from parafollicular C cells. MTC is a rare disease, but its prognosis is less favorable than that of well-differentiated thyroid cancers. To improve the prognosis of patients with MTC, early diagnosis and prompt therapeutic management are crucial. In the following paper, recent advances in laboratory and imaging diagnostics and also pharmacological and surgical therapies of MTC are discussed. Currently, a thriving direction of development for laboratory diagnostics is immunohistochemistry. The primary imaging modality in the diagnosis of MTC is the ultrasound, but opportunities for development are seen primarily in nuclear medicine techniques. Surgical management is the primary method of treating MTCs. There are numerous publications concerning the stratification of particular lymph node compartments for removal. With the introduction of more effective methods of intraoperative parathyroid identification, the complication rate of surgical treatment may be reduced. The currently used pharmacotherapy is characterized by high toxicity. Moreover, the main limitation of current pharmacotherapy is the development of drug resistance. Currently, there is ongoing research on the use of tyrosine kinase inhibitors (TKIs), highly specific RET inhibitors, radiotherapy and immunotherapy. These new therapies may improve the prognosis of patients with MTCs.

An Appraisal and Update of Fluorodeoxyglucose and Non-Fluorodeoxyglucose-PET Tracers in Thyroid and Non-Thyroid Endocrine Neoplasms

Endocrine neoplasms and malignancies are a diverse group of tumors with varied clinical, histopathologic, and functional features. These tumors vary from sporadic to hereditary, isolated entities to multiple neoplastic syndromes, functioning and non functioning tumors, unifocal locally invasive, and advanced to multifocal tumors with disseminated distant metastases. The presence of various specific biomarkers and specific receptor targets serves as valuable tools for diagnosis, prognosis, and management. PET-CT with FDG and a multitude of novel and specific radiotracers towards specific therapeutic targets mandates personalization of their use, so as to ensure maximum clinical benefit in the management of these neoplasms.

Functional imaging in thyroid cancer patients with metastases and therapeutic implications

Functional imaging plays a central role in the management of thyroid cancer patients. In patients with a differentiated thyroid cancer (DTC), radioactive iodine (RAI) is used mostly with a therapeutic intent, either post-operatively or as the first line systemic treatment in patients with known structural disease. A whole body scan is performed a few days after the RAI administration, and this procedure is very sensitive to detect all tumor foci with RAI uptake. PET/CT with ¹⁸F-FDG complements the use of RAI at the initial evaluation of patients with high-risk DTC, during follow-up in those with rising serum thyroglobulin levels over time, for the work-up of patients with documented structural disease and for assessing the efficacy of focal or systemic treatment modalities. ¹⁸F-FDG uptake is a prognostic indicator in all these clinical conditions. A dosimetric approach with ¹²⁴I PET/CT showed encouraging results. Several functional imaging modalities are currently available for medullary thyroid carcinoma (MTC) patients. ¹⁸F-FDG-PET/CT may be sensitive in MTC patients with high FDG uptake that signals aggressive disease. ¹⁸F-DOPA is the most sensitive imaging technique to visualize small tumor foci, and is also highly specific in patients with a known MTC, but should be complemented by a CT scan of the chest and by a MRI of the liver to detect small metastases.

Metastatic medullary thyroid carcinoma: a new way forward

Medullary thyroid carcinoma (MTC) is a rare malignancy comprising 1-2% of all thyroid cancers in the United States. Approximately 20% of cases are familial, secondary to a germline RET mutation, while the remaining 80% are sporadic and also harbour a somatic RET mutation in more than half of all cases. Up to 15-20% of patients will present with distant metastatic disease, and retrospective series report a 10-year survival of 10-40% from time of first metastasis. Historically, systemic therapies for metastatic MTC have been limited, and cytotoxic chemotherapy has demonstrated poor objective response rates. However, in the last decade, targeted therapies, particularly multitargeted tyrosine kinase inhibitors (TKIs), have demonstrated prolonged progression-free survival in advanced and progressive MTC. Both cabozantinib and vandetanib have been approved as first-line treatment options in many countries; nevertheless, their use is limited by high toxicity rates and dose reductions are often necessary. New generation TKIs, such as selpercatinib or pralsetinib, that exhibit selective activity against RET, have recently been approved as a second-line treatment option, and they exhibit a more favourable side-effect profile. Peptide receptor radionuclide therapy or immune checkpoint inhibitors may also constitute potential therapeutic options in specific clinical settings. In this review, we aim to present all current therapeutic options available for patients with progressive MTC, as well as new or as yet experimental treatments.

Imaging medullary thyroid cancer patients with detectable serum markers: state of the art and future perspectives

PURPOSE

Medullary thyroid carcinoma (MTC) originates from thyroid parafollicular C-cells and represents <5% of all thyroid cancers. Serum Calcitonin (CTn) is considered the most sensitive marker of persistent or recurrent disease and is measured in association to CEA. According to the American Thyroid Association (ATA) guidelines, following initial surgery when CTn level remains below 150 pg/mL, follow-up may rely on repeated serum marker determinations and on neck ultrasonography (US). When CTn level exceeds 150 pg/ml, additional imaging is required. In this review, we provide an overview of available imaging tools to monitor MTC course and propose an effective imaging strategy for MTC patients according to their clinical situation.

METHODS

A literature search focusing on available imaging tools to monitor MTC provided the currently available information for this review. Recent evidence-based reports and reviews were considered as priority over older evidence.

RESULTS

For MTC patients with detectable CTn levels and disease recurrence, PET/CT imaging with ¹⁸F-DOPA or ⁶⁸Ga-DOTA-peptides present the best sensitivity for lesion detection. ¹⁸F FDG PET/CT represents a prognostic tool and is useful in case of aggressive disease. Neck ultrasound, chest CT scan and MRI of the liver and of the axial skeleton represent complementary techniques. Beyond the diagnostic accuracy, the clinical impact of imaging is variable according to different disease settings and tumor marker levels. Finally, other applications of imaging such as response to focal and systemic treatments and new promising PET tracers should be further investigated.

CONCLUSION

The role of imaging in MTC patients improved, especially with the use of ¹⁸F-DOPA PET/CT that provides high quality diagnostic images. However, the impact on therapeutic management should be further evaluated in the different disease settings and in proper prospective trials.

Visualization of Tumor Heterogeneity in Advanced Medullary Thyroid Carcinoma by Dual-Tracer Molecular Imaging: Revealing the Theranostic Potential of SSTR- and PSMA-Directed Endoradiotherapy

ABSTRACT

We present the case of a 60-year-old man with medullary thyroid carcinoma and hepatic, osseous, and lymph node metastases who underwent peptide receptor radionuclide therapy with 177Lu-DOTATOC. After 2 cycles, 68Ga-DOTATOC PET/CT revealed multiple nonavid lesions. To assess whether the patient would be eligible for prostate-specific membrane antigen (PSMA)-targeted radioligand therapy, a PSMA PET/CT was conducted. PSMA PET/CT identified increased PSMA expression in both 68Ga-DOTATOC-avid and nonavid lesions. As such, dual-radiotracer PET/CT may allow for insights into the complexities of tumor heterogeneity in patients with medullary thyroid carcinoma, which may pave the way for subsequent therapeutic algorithms.

Peptide Receptor Radionuclide Therapy in Thyroid Cancer

The treatment options that are currently available for management of metastatic, progressive radioactive iodine (RAI)-refractory differentiated thyroid cancers (DTCs), and medullary thyroid cancers (MTCs) are limited. While there are several systemic targeted therapies, such as tyrosine kinase inhibitors, that are being evaluated and implemented in the treatment of these cancers, such therapies are associated with serious, sometimes life-threatening, adverse events. Peptide receptor radionuclide therapy (PRRT) has the potential to be an effective and safe modality for treating patients with somatostatin receptor (SSTR)+ RAI-refractory DTCs and MTCs. MTCs and certain sub-types of RAI-refractory DTCs, such as Hürthle cell cancers which are less responsive to conventional modalities of treatment, have demonstrated a favorable response to treatment with PRRT. While the current literature offers hope for utilization of PRRT in thyroid cancer, several areas of this field remain to be investigated further, especially head-to-head comparisons with other systemic targeted therapies. In this review, we provide a comprehensive outlook on the current translational and clinical data on the use of various PRRTs, including diagnostic utility of somatostatin analogs, theranostic properties of PRRT, and the potential areas for future research.

Metastatic Medullary Thyroid Cancer: The Role of 68Gallium-DOTA-Somatostatin Analogue PET/CT and Peptide Receptor Radionuclide Therapy

CONTEXT

Metastatic medullary thyroid cancer (MTC) is a rare malignancy with minimal treatment options. Many, but not all, MTCs express somatostatin receptors.

OBJECTIVE

Our aim was to explore the role of 68Ga-DOTA-somatostatin analogue (SSA) positron emission tomography (PET)/computed tomography (CT) in patients with metastatic MTC and to determine their eligibility for peptide receptor radionuclide therapy (PRRT).

METHODS

We retrospectively identified patients with metastatic MTC who had 68Ga-DOTA-SSA PET/CT at 5 centers. We collected characteristics on contrast-enhanced CT, 68Ga-DOTA-SSA and 18F-FDG PET/CT. The efficacy of PRRT was explored in a subgroup of patients. Kaplan-Meier analysis was used to estimate time to treatment failure (TTF) and overall survival (OS).

RESULTS

Seventy-one patients were included (10 local recurrence, 61 distant disease). Of the patients with distant disease, 16 (26%) had ≥50% of disease sites with tracer avidity greater than background liver, including 10 (10/61, 16%) with >90%. In 19 patients with contemporaneous contrast-enhanced CT, no disease regions were independently identified on 68Ga-DOTA-SSA PET/CT. Thirty-five patients had an 18F-FDG PET/CT, with 18F-FDG positive/68Ga-DOTA-SSA negative metastases identified in 15 (43%). Twenty-one patients had PRRT with a median TTF of 14 months (95% CI 8-25) and a median OS of 63 months (95% CI 21-not reached). Of the entire cohort, the median OS was 323 months (95% CI 152-not reached). Predictors of poorer OS included a short calcitonin doubling-time (≤24 months), strong 18F-FDG avidity, and age ≥60 years.

CONCLUSIONS

The prevalence of high tumor avidity on 68Ga-DOTA-SSA PET/CT is low in the setting of metastatic MTC; nevertheless, PRRT may still be a viable treatment option in select patients.

Medullary thyroid carcinoma

PURPOSE OF REVIEW

To summarize recent developments in the diagnosis and management of patients with medullary thyroid cancer (MTC), with a focus on pathogenesis, systemic therapy, and future directions.

RECENT FINDINGS

The addition of mutational analysis to cytological assessment of thyroid nodules has improved the diagnostic accuracy of MTC. The discovery of new genomic alterations and overexpression of certain factors allows for improved prognostication in MTC and provides potentially new therapeutic agents. New data suggest that tumor environment may be more immunogenic than previously thought in a subset of MTCs with identification of a new MTC-specific antigen leading to a revival of investigating immune-based therapy for this disease. The newly approved selective rearranged during transfection (RET0-inhibitors, selpercatinib and pralsetinib, offer promising results, and tolerability for patients with RET-mutated MTC; however, the development of resistance mechanisms may be problematic.

SUMMARY

MTC has witnessed remarkable advancements in recent years. Our new understanding of some of the driver mutations in MTC allows for therapeutics with more tolerable adverse event profiles. However, there is still a need for more effective treatment strategies for subsets of patients without actionable mutations and for those who develop resistance to currently available therapies.

Anti-CEA Pretargeted Immuno-PET Shows Higher Sensitivity Than DOPA PET/CT in Detecting Relapsing Metastatic Medullary Thyroid Carcinoma: Post Hoc Analysis of the iPET-MTC Study

Pretargeting parameters for the use of anti-carcinoembryonic antigen (CEA) bispecific monoclonal antibody TF2 and the 68Ga-labeled IMP288 peptide for immuno-PET have been optimized in a first-in-humans study performed on medullary thyroid carcinoma (MTC) patients (the iPET-MTC study). The aim of this post hoc analysis was to determine the sensitivity of immuno-PET in relapsing MTC patients, in comparison with conventional imaging and 18F-l-dihydroxyphenylalanine (18F-DOPA) PET/CT. Methods: Twenty-five studies were analyzed in 22 patients. All patients underwent immuno-PET 1 and 2 h after 68Ga-IMP288 injection pretargeted by TF2, in addition to neck, thoracic, abdominal, and pelvic CT; bone and liver MRI; and 18F-DOPA PET/CT. The gold standard was histology or confirmation by one other imaging method or by imaging follow-up. Results: In total, 190 lesions were confirmed by the gold standard: 89 in lymph nodes, 14 in lungs, 46 in liver, 37 in bone, and 4 in other sites (subcutaneous tissue, heart, brain, and pancreas). The number of abnormal foci detected by immuno-PET was 210. Among these, 174 (83%) were confirmed as true-positive by the gold standard. Immuno-PET showed a higher overall sensitivity (92%) than 18F-DOPA PET/CT (65%). Regarding metastatic sites, immuno-PET had a higher sensitivity than CT, 18F-DOPA PET/CT, or MRI for lymph nodes (98% vs. 83% for CT and 70% for 18F-DOPA PET/CT), liver (98% vs. 87% for CT, 65% for 18F-DOPA PET/CT, and 89% for MRI), and bone (92% vs. 64% for 18F-DOPA PET/CT and 86% for MRI), whereas sensitivity was lower for lung metastases (29% vs. 100% for CT and 14% for 18F-DOPA PET/CT). Tumor SUVmax at 60 min ranged from 1.2 to 59.0, with intra- and interpatient variability. Conclusion: This post hoc study demonstrates that anti-carcinoembryonic antigen immuno-PET is an effective procedure for detecting metastatic MTC lesions. Immuno-PET showed a higher overall sensitivity than 18F-DOPA PET/CT for disclosing metastases, except for the lung, where CT remains the most effective examination.

Evaluation of F-18 DOPA PET/CT in the detection of recurrent or metastatic medullary thyroid carcinoma: comparison with GA-68 DOTA-TATE PET/CT

OBJECTIVE

PET imaging with F-18 DOPA (FDOPA) and Ga-68 DOTATATE (TATE) shows the most promising results to detect medullary thyroid cancer (MTC) recurrence. We performed this comparative study to detect the site of recurrent or metastatic disease in MTC patients with elevated serum calcitonin (Ctn) and/or carcinoembryonic antigen (CEA) levels.

METHODS

We studied 46 MTC patients (25 women, 21 men) with elevated Ctn and/or CEA levels during follow-up who had both FDOPA and TATE PET/CT scans for re-staging purposes.

RESULTS

FDOPA PET imaging yielded an overall sensitivity of 86.8%, specificity of 100%, PPV of 100%, NPV of 61.5%, and accuracy of 89.1%, while TATE PET scan had the same values as 84.2%, 87.5%, 96.9%, 53.8%, and 84.6%, respectively, and there was no statistically significant difference between the two modalities with the exception of the specificity value that was higher for FDOPA imaging. In a subgroup of patients with overt Ctn or CEA elevation, sensitivity of FDOPA increased significantly, whereas TATE sensitivity did not change. FDOPA PET imaging was significantly superior in detecting liver and regional lymph node (LN) metastases, while TATE PET scan was significantly better in the skeletal metastases. Early FDOPA demonstrated 11 invisible lesions on late FDOPA.

CONCLUSION

Both FDOPA and TATE PET/CT imaging are useful to localize recurrences in MTC patients. While TATE imaging is superior to reveal skeletal disease, FDOPA seems better in liver and regional LN metastases; therefore, the two modalities appear complementary in monitoring MTC patients with elevated serum Ctn and/or CEA levels.

Knowns and unknowns of bone metastases in patients with neuroendocrine neoplasms: A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to develop an evidence-based summary of current knowledge of bone metastases (BMs) in neuroendocrine neoplasms (NENs), inform diagnosis and treatment and standardise management between institutions.

METHODS

PubMed, Medline, EMBASE and meeting proceedings were searched for eligible studies reporting data on patients with BMs and NENs of any grade of differentiation and site; poorly-differentiated large/small cell lung cancer were excluded. Data were extracted and analysed using STATA v.12. Meta-analysis of proportions for calculation of estimated pooled prevalence of BM and calculation of weighted pooled frequency and weighted pooled mean for other variables of interest was performed .

RESULTS

A total of 149 studies met the eligibility criteria. Pooled prevalence of BMs was 18.4% (95% CI 15.4-21.5). BMs were mainly metachronous with initial diagnosis of NEN (61.2%) and predominantly osteoblastic; around 61% were multifocal, with a predisposition in axial skeleton. PET/CT seemed to provide (together with MRI) the highest sensitivity and specificity for BM detection. Almost half of patients (46.4%) reported BM-related symptoms: pain (66%) and skeletal-related events (SREs, fracture/spinal cord compression) (26.2%; weightedweighted mean time-to-SRE 9.9 months). Management of BMs was multimodal [bisphosphonates and bone-modifying agents (45.2%), external beam radiotherapy (34.9%), surgery (14.8%)] and supported by little evidence. Overall survival (OS) from the time of diagnosis of BMs was long [weighted mean 50.9 months (95% CI 40.0-61.9)]. Patients with BMs had shorter OS [48.8 months (95% CI 37.9-59.6)] compared to patients without BMs [87.4 months (95% CI 74.9-100.0); p = 0.001]. Poor performance status and BM-related symptoms were also associated with worse OS.

CONCLUSIONS

BMs in patients with NENs remain underdiagnosed and undertreated. Recommendations for management of BMs derived from current knowledge are provided. Prospective studies to inform management are required.

Medullary thyroid carcinoma: recent advances in identification, treatment, and prognosis

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor that represents <5% of all thyroid malignancies and is generally more aggressive than differentiated thyroid cancer. The aim of this study is to provide an update, through review of clinical studies of patients with MTC published between January 1, 2016, and June 1, 2021, on recent advances in the diagnosis and treatment of MTC. This review focuses on updates in biochemical testing, imaging, hereditary disease, surgical management, adjuvant therapies, and prognosis. Recent advances reviewed herein have sought to diagnose MTC at earlier stages of disease, predict when patients with a hereditary syndrome may develop MTC, use functional imaging to assess for distant metastases, perform optimal initial surgery with appropriate lymphadenectomy, employ targeted systemic therapies for patients with progressive metastatic disease, and better predict patient-specific outcomes.

Comparison of 18F-NaF PET/CT with Other Imaging Methods in the Detection of Bone Metastases in Patients with Medullary Thyroid Cancer: a Report of a Series of 31 Cases

PURPOSE

To compare the 18F-NaF PET/CT studies (18F-NaF) with other imaging methods in the detection of skeletal metastases (SM) in patients with medullary thyroid cancer (MTC).

METHODS

We retrospectively analyzed 31 patients with MTC who performed 18F-NaF to assess SM. The results of the 18F-NaF were compared with other imaging methods performed for metastasis detection: 99Tc-MDP bone scan (BS), magnetic resonance imaging (MRI), contrast-enhanced CT (CT), and 68Ga-Dotatate and 18F-FDG PET/CT studies. A qualitative analysis comparing the 18F-NaF findings with the ones of the other methods was performed, and the results were classified as superior (>), equal (=), and inferior (<).

RESULTS

Eleven patients had no bone metastases detected on any of the imaging methods used. Twenty patients presented SM depicted on 18F-NaF. Of these 20 patients, 12 performed bone scan (in 9 18F-NaF > BS and in 3 18F-NaF = BS), 1 performed 18F-FDG (18F-NaF > 18F-FDG), 4 performed 68Ga-Dotatate (in 2 18F-NaF > 68Ga-Dotatate and in 2 18F-NaF = 68Ga-Dotatate), 20 performed CT of at least one body segment (in 15 18F-NaF = CT and in 5 18F-NaF > CT), and 16 performed MRI of at least one body segment, and in all of them, the 18F-NaF was equal to the MRI. Beside this, the 18F-NaF detected SM in body segments not routinely scanned in MRI and CT.

CONCLUSION

In patients with MTC, the 18F-NaF seems to be equal or superior to other imaging modalities in the detection of SM and allows the analysis of the whole skeletal in a single study.

68Ga-DOTATATE PET/MRI for Neuroendocrine Tumors: A Pictorial Review

Neuroendocrine tumors (NETs) constitute a variety of neoplastic entities and exhibit variable degrees of neuroendocrine differentiation and phenotypes, as well as genetic profiles. Ga-DOTATATE PET is a novel imaging technique for NET. Although PET/CT is commonly utilized for oncologic imaging, PET/MRI is particularly suited for NETs, as MRI provides greater soft tissue contrast than CT, allowing for improved detection and characterization of NETs, particularly when liver metastasis is suspected or needs to be ruled out. The current pictorial review aims to illustrate the complementary advantages, as well as pitfalls of Ga-DOTATATE PET/MRI in the evaluation of NETs.

Imaging with radiolabelled bisphosphonates

Radiolabeled bisphosphonates were developed in the 1970s for scintigraphic functional imaging of the skeleton in benign and malignant disease. Tracers such as 99mTc-methylene diphosphonate, that map focal or global changes in mineralization in the skeleton qualitatively and quantitatively, have been the backbone of nuclear medicine imaging for decades. While competing technologies are evolving, new indications and improvements in scanner hardware, in particular hybrid imaging (e.g. single photon emission computed tomography combined with computed tomography), have allowed improved diagnostic accuracy and a continued role for radiolabeled bisphosphonate imaging in current practice.

Medullary thyroid cancer: molecular factors, management and treatment

Medullary thyroid cancer (MTC) is an infrequent neuroendocrine tumor, which amounts to 3-5% of all thyroid malignancies. Approximately 75-80% of MTCs are sporadic neoplasms. The rest of 20-25% are familial cases that belong to multiple endocrine neoplasia (MEN) syndromes, specifically MEN2 and MEN3. These cases of familial MTC are attributed to an activating germline mutation of a tyrosine kinase receptor gene, the rearranged during transfection (RET) proto-oncogene, located on chromosome 10q11.21. These mutations are also found in some cases of sporadic MTC. This review sets forth in summary the accepted guidelines and approaches regarding diagnosis, management, and treatment of MTC. Surgical resection is the standard care, and an early, prophylactic intervention is performed in genetic cases. Further investigation and understanding of the molecular pathways involved in the growth and advancement of MTC is required in order to provide efficient therapy in cases of progressive disease.

Clinical impact of 68Ga-DOTATATE PET-CT imaging in patients with medullary thyroid cancer

PURPOSE

Medullary thyroid cancer (MTC) arises from neuroendocrine C cells of the thyroid. There is no single diagnostic imaging method that can reveal all MTC recurrences or metastases. ⁶⁸Ga-DOTATATE is an alternative PET radiotracer that showed acceptable efficacy in the detection of MTC. In this study, we aimed to reveal the clinical efficacy and impact of this radiotracer on the management of patients with MTC.

METHODS

The ⁶⁸Ga-DOTATATE PET-CT records of 38 patients with confirmed MTC were included in the study. The demographic data, clinical indication for the scan, previous therapies, and tumor marker levels were recorded. The site and SUVmax of the lesions were also noted. A consensus was reached on the additional value of ⁶⁸Ga-DOTATATE PET-CT, and sites with discordant results on conventional imaging (CI). Finally, changes in management after the scan were evaluated.

RESULTS

⁶⁸Ga-DOTATATE PET-CT outperformed CI in 14/38 (37%) patients. In these 14 patients, metastatic lymph nodes were detected in 8, bone metastases in 4, and both bone and lymph nodes metastases in 2 patients. In 16/38 (42%) patients, ⁶⁸Ga-DOTATATE PET-CT performed equally well as CI. In 5/38 (13%) patients, CI outperformed PET-CT. Most of the patients (4/5) in this group had hepatic metastases. ⁶⁸Ga-DOTATATE PET-CT positivity was also correlated with tumor marker expression [median calcitonin; PET-positive: 743 ± 5439 vs PET-negative: 45 ± 17 (p:0.012), median CEA; PET-positive: 41 ± 162 vs PET-negative: 2.6 ± 1.4 (p:0.015)]. ⁶⁸Ga-DOTATATE PET-CT changed the clinical management of 13/38 (34%) patients. The information provided by PET-CT resulted in neck surgery in 5/13 patients, external radiotherapy in 3/13 and both in one patient. Four of these thirteen patients were found to be eligible for peptide receptor radionuclide therapy.

CONCLUSION

⁶⁸ Ga-DOTATATE is an essential part of the work-up for patients with MTC. This modality outperformed CI in 14/38 (37%) patients and changed the clinical management in 13/38 (34%) patients. Prospective randomized studies with image-guided therapy decisions are needed to further reveal the impact of PET imaging in patients with MTC.

Medullary Thyroid Carcinoma: An Update on Imaging

Medullary thyroid carcinoma (MTC), arising from the parafollicular C cells of the thyroid, accounts for 1–2% of thyroid cancers. MTC is frequently aggressive and metastasizes to cervical and mediastinal lymph nodes, lungs, liver, and bones. Although a number of new imaging modalities for directing the management of oncologic patients evolved over the last two decades, the clinical application of these novel techniques is limited in MTC. In this article, we review the biology and molecular aspects of MTC as an important background for the use of current imaging modalities and approaches for this tumor. We discuss the modern and currently available imaging techniques—advanced magnetic resonance imaging (MRI)-based techniques such as whole-body MRI, dynamic contrast-enhanced (DCE) technique, diffusion-weighted imaging (DWI), positron emission tomography/computed tomography (PET/CT) with 18F-FDOPA and 18F-FDG, and integrated positron emission tomography/magnetic resonance (PET/MR) hybrid imaging—for primary as well as metastatic MTC tumor, including its metastatic spread to lymph nodes and the most common sites of distant metastases: lungs, liver, and bones.

CT- and ultrasound-characteristics of hepatic lesions in patients with multiple endocrine neoplasia syndrome. A retrospective image review of 25 cases

Introduction

Liver metastases from neuroendocrine tumors in multiple endocrine neoplasia syndrome are common (75%) and significantly impairs the prognosis. Characterisation of liver lesions in these patients is challenging, as liver metastases are difficult to differentiate from benign liver lesions such as haemangioma.

Methods

In this study we aimed to characterize the radiological findings of hepatic metastases in MEN patients. The findings of contrast-enhanced CT were considered for the main diagnosis. We retrospectively evaluated 25 patients with MEN-syndrome (10 MEN1/ 15 MEN2) including 11 men and 14 women between 28–62 years of age.

Results

Liver metastases (48%, 12/25) and hemangioma (40%, 10/25) were the most common liver lesions among our patients. The most common primary tumors in our MEN1 and MEN2 patients with liver metastases were of pancreatic neuroendocrine tumor (70%, 7/10) und medullary thyroid carcinoma (100%, 15/15) origin, respectively. CT-characteristics were grouped into three main categories, depending on contrast dynamics. The majority of hepatic metastases (75%, 14/25) are presented as multiple lesions with a slow growth in an average 5 years of follow-up-period. We were able to find a common CT pattern and categorise these for each MEN-syndrome. Hepatic metastases in MEN1 presented commonly a blurred arterial enhancement with a low portal venous enhancement and less frequently a prominent enhancement in the arterial phase, which mimics the classical haemangioma. In MEN2 the liver metastases exhibited disseminated mixed hyper- and hypo-enhanced lesions in CT-scans. Moreover, lesion calcifications are pathognomonic in MEN2. The main limitation of this study is the missing histopathological confirmation in the majority of cases.

Conclusions

In this retrospective imaging study, we were able to categorise and find a common CT pattern for hepatic lesions in patients with MEN-syndrome. In order to differentiate these lesions sufficiently, a combination of a 3-phasic CT-scan with US is required. Other liver specific imaging modalities (MRI, CEUS, SMS-PET/CT) should complement the diagnosis in individual cases.

Current Standards and Recent Advances in Biomarkers of Major Endocrine Tumors

The complexity of endocrine tumor diagnosis stems from its variable symptoms and presentation that may mimic many other disease states, or display asymptomatic properties for a prolonged amount of time. Early and accurate disease identification is needed for better patient prognosis. The key to this may be in using validated biomarkers with enhanced sensitivity and specificity. Several biomarkers are consistently used across various endocrine tumor types, possibly indicating a deeper pathophysiological mechanism behind endocrine cancer genesis and development. For example, carbohydrate antigen (CA) is measured in both pancreatic adenocarcinoma as well as ovarian cancer for diagnosis, surveillance, and risk stratification. The discovery of measuring miRNAs that are highly expressed in malignant tumors is also a novel strategy across multiple endocrine tumor types, and is propelling the future advancement of biomarker development. This review introduces currently utilized biomarkers in some of the commonly known endocrine tumors, including thyroid, adrenal, pituitary, pancreatic, and gonadal carcinoma, as well as future research directions.