Merkel Cell Carcinoma: Is there a Role for 2-Deoxy-2-[F-18]fluoro-d-glucose-Positron Emission Tomography/Computed Tomography?

Diagnostic Test Accuracy of 18 F-FDG PET or PET/CT in Merkel Cell Carcinoma

OBJECTIVE

The purpose of the current study was to evaluate the diagnostic accuracies of 18 F-FDG PET or PET/CT for diagnosis of Merkel cell carcinoma (MCC) through a systematic review and meta-analysis.

METHODS

The PubMed, Cochrane database, and EMBASE database, from January 1990 to January 31, 2022, were searched for studies evaluating diagnostic performance of 18 F-FDG PET or PET/CT for MCC. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

Across 9 studies (259 patients), the pooled sensitivity of 18 F-FDG PET or PET/CT was 0.91 (95% confidence interval [CI], 0.85-0.95) and a pooled specificity of 0.93 (95% CI, 0.86-0.97). Likelihood ratio syntheses gave an overall LR+ of 14.0 (95% CI, 6.6-29.6) and LR- of 0.09 (95% CI, 0.05-0.17). The pooled diagnostic odds ratio was 153 (95% CI, 57-416).

CONCLUSION

18 F-FDG PET/CT showed an excellent performance for diagnosis of MCC. The likelihood ratio scattergram indicated that 18 F-FDG PET or PET/CT is useful for exclusion and confirmation of MCC. Further large multicenter studies would be necessary to substantiate the diagnostic accuracy of 18 F-FDG PET or PET/CT for MCC patients.

The role of 18F-FDG PET/CT in the management of Merkel cell carcinoma: The experience of 51 studies in our institution

OBJECTIVES

Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine tumor with limited evidence on the role of ¹⁸F-FDG PET/CT. The aim of this study was to assess the impact of the ¹⁸F-FDG PET/CT in the management of MCC.

METHODS

Fifty-one studies of ¹⁸F-FDG PET/CT of 35 patients (19 men [54.30%]; 72.17±14.63years) with histologic diagnosis of MCC were retrospectively evaluated. The change in tumor staging and the impact on the treatment were analysed.

RESULTS

There were 23 PET/CT positive studies (45.10%) and 28 (54.90%) negative. Thirty four (66.7%) studies were performed for assessment of stage at initial presentation and 17 (33.3%) were performed during the follow up: 6 (35.29%) for suspected recurrence; 7 (41.18%) for restaging; 4 (23.53%) as a part of ongoing surveillance. On the basis of PET/CT results, there was a change in disease stage (SC) in 20 studies (39.20%) and impact in the management (MI) in 28 (54.90%): 11 (32.40%) SC and 12 (35.30%) MI in the initial staging; 5 (71.43%) SC and 7 (100%) MI in the restaging; 3 (50.00%) SC and 6 (100%) MI in suspected recurrence; 1 (25.00%) SC and 3 (75.00%) MI in the surveillance. ¹⁸F-FDG PET/CT incidentally detected one additional histologically confirmed cancer. The presence of nodal involvement in the beginning (0.0098; HR 3.82; 95%CI: 1.38-10.6), chemotherapy treatment (6e-04; HR 7.06; 95%CI: 2.30-21.60), size of primary tumor >2cm (6e-04; HR 7.06; 95%CI: 2.30-21.60) and positive resection margin (0.00069; HR 4.01; 95%CI: 1.46-11.00) were statistically significant prognostic factors for overall survival. There was a trend towards significance for worse overall survival with initial positive ¹⁸F-FDG PET/CT but the trend did not reach statistical significance.

CONCLUSION

¹⁸F-FDG PET/CT altered the stage in 2 out of 5 studies and changed the treatment in more than half of the studies performed. The study confirms the important impact of ¹⁸F-FDG PET/CT on the management of MCC patients.

Positron Emission Tomography in Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare neuroendocrine skin malignancy usually arising as a nonspecific nodule on sun-exposed areas of the head and neck. Given the poor prognosis of this aggressive tumor, assessment of disease burden in pre- and post-treatment care may ensure an optimal management with significant implications for patient surveillance and prognosis. Although imaging has established its role in locally advanced or distant metastatic MCC, a standard imaging algorithm is yet to be determined and respective recommendations are mainly based on melanoma. Positron emission tomography/computed tomography (PET/CT) is increasingly evolving as a valuable imaging tool in metastatic or unresectable MCC, mostly utilizing the glucose analogue 18F-fluorodeoxyglucose (18F-FDG) as a radiotracer. Despite being inferior in detecting the disease in its early stages compared to the "gold standard" of sentinel lymph node biopsy, recent evidence suggests an important role for 18F-FDG PET/CT in the routine workup of localized MCC. Moreover, 68Ga-labeled somatostatin analogues have been employed as PET tracers in the field of MCC with promising, yet comparable to 18F-FDG, results. This article provides a structured literature review of the most important studies investigating the role of PET or PET/CT in the clinical practice of MCC.

18F-FDG PET/CT for Monitoring Response of Merkel Cell Carcinoma to the Novel Programmed Cell Death Ligand 1 Inhibitor Avelumab

An 85-year-old man with stage IIIA Merkel cell carcinoma of the left arm was initially treated with local excision and axillary node dissection followed by radiation therapy. Eight months after surgery, whole-body FDG PET/CT demonstrated intensely hypermetabolic hepatic metastases and abdominal lymphadenopathy. Given his age and comorbidities, he was considered a poor candidate for chemotherapy, and therefore the novel programmed cell death ligand 1 inhibitor avelumab was initiated. FDG PET/CT after 4 cycles showed complete resolution of hepatic and nodal metastases. Whole-body FDG PET/CT can be used for monitoring response of multisystem metastases from Merkel cell carcinoma to active immunotherapy.

The utility of positron emission tomography with and without computed tomography in patients with nonmelanoma skin cancer

Combined positron emission tomography (PET) and computed tomography (CT) scans are widely used in the staging and monitoring of most malignancies. The differential for PET-positive cutaneous lesions includes primary skin cancers, infections, cutaneous metastases from distant malignancies, and benign neoplasms. In dermatology, PET/CT scans have been most widely studied in patients with melanoma and Merkel cell carcinoma. The role of PET/CT scans in the management of other cutaneous malignancies is less clear, but it has shown great promise in the management of patients with squamous cell carcinoma and cutaneous lymphoma. This review seeks to address the usefulness of PET/CT scans in nonmelanoma skin cancer and to provide guidance regarding the management of patients with incidental PET-positive nodules. Currently, there is limited experience with PET/CT scans for staging and monitoring of non-head and neck metastatic basal cell and squamous cell carcinomas, and results show limited sensitivity and specificity. We also address the evidence for management of an incidental PET-positive cutaneous nodule and recommend obtaining a biopsy specimen in patients with a known noncutaneous malignancy, a history of primary skin cancer, or a high risk of either cutaneous or noncutaneous malignancy.

Merkel cell carcinoma: emerging biology, current approaches, and future directions

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine cutaneous cancer that predominantly occurs in patients who are older, and is associated with a high rate of distant failure and mortality. Current management strategies that incorporate surgery and radiotherapy achieve high rates of locoregional control, but distant failure rates remain problematic, highlighting the need for new effective systemic therapies. Chemotherapy can achieve high response rates of limited duration in the metastatic setting, but its role in definitive management remains unproven. Recent developments in our knowledge about the biology of MCC have led to the identification of new potential therapeutic targets and treatments. A key finding has been the discovery that a human polyomavirus may be a causative agent. However, emerging data suggests that MCC may actually be two distinct entities, viral-associated and viral-negative MCC, which is likely to have implications for the management of MCC in the future and for the development of new treatments. In this review, we discuss recent discoveries about the biology of MCC, current approaches to management, and new therapeutic strategies that are being investigated.

A case series and literature review of Merkel cell carcinoma metastasizing to pancreas

BACKGROUND

Merkel cell carcinoma is a rare aggressive tumor arising from the mechanoreceptors of the epidermis with a relative higher mortality rate stage for stage than melanoma. Microscopically, the cells appear similar to small cell lung cancer, but they specifically stain positive for CK20 and are negative for TTF-1. It is rarely known to metastasize to the pancreas.

AIMS

To report four cases of Merkel cell carcinoma metastasizing to pancreas and compare them to previously reported patients.

METHODS

We performed a retrospective review of all patients who underwent endoscopic ultrasound with fine-needle aspiration (EUS-FNA) for a suspected pancreatic lesion between January 2004 and December 2012. We reviewed other reported cases with a literature search using PubMed, Embase, and Scopus.

RESULTS

Four male patients with mean age of 66 years were found to have metastatic disease in the pancreas on average 29 months after initial diagnosis of MCC. Two cases were diagnosed with EUS-FNA and two with PET-CT. Three patients had multifocal pancreatic involvement which has not been previously described. All four patients died within 3-9 months following tumor spread to the pancreas. Merkel cell carcinoma rarely metastasizes to the pancreas with only 10 cases being described in the medical literature.

CONCLUSIONS

EUS-FNA is an effective tool that can be utilized in diagnosing pancreatic masses. Differentiating metastatic pancreatic tumors, especially Merkel cell carcinoma from primary pancreatic tumor is useful as systemic therapy is an option in pancreatic adenocarcinoma, but is ineffective in metastatic Merkel cell carcinoma.

Focus on Merkel cell carcinoma: diagnosis and staging

Merkel cell carcinoma is a rare lymphophilic skin tumor of neuroendocrine origin with the potential for rapid progression. Small, localized lesions are diagnosed and treated clinically, but advanced tumors often undergo imaging evaluation. Due to its rarity, radiologists are unaware of evocative imaging features and usually do not consider Merkel cell carcinoma in the differential diagnosis of soft tissue tumors. Appropriate staging is important to determine appropriate treatment and has an impact on patient prognosis. Multimodality imaging is usually needed, and there is no consensus on the optimal imaging strategy. The purpose of this article is to review various aspects of Merkel cell carcinoma imaging and look in detail at how optimal multimodality staging should be carried out.

Molecular imaging and therapy of merkel cell carcinoma

Several molecular imaging modalities have been evaluated in the management of Merkel cell carcinoma (MCC), a rare and aggressive tumor with a high tendency to metastasize. Continuous progress in the field of molecular imaging might improve management in these patients. The authors review the current modalities and their impact on MCC in this brief review article.

Diagnostic performance of fluorine-18-fluorodeoxyglucose positron emission tomography in patients with Merkel cell carcinoma: a systematic review and meta-analysis

BACKGROUND

Some studies reported the usefulness of fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and PET/computed tomography (CT) in patients with Merkel cell carcinoma (MCC).

OBJECTIVE

The aim of this study was to systematically review and meta-analyze published data about the diagnostic performance of 18F-FDG PET and PET/CT in patients with MCC.

METHODS

A comprehensive literature search of studies published through June 2013 regarding 18F-FDG PET and PET/CT in patients with MCC was performed. All retrieved studies were reviewed and qualitatively analyzed. Pooled sensitivity, specificity, positive and negative likelihood ratio (LR+ and LR−) and diagnostic odds ratio (DOR) of 18F-FDG PET or PET/CT in patients with MCC on a per examination-based analysis were calculated. The area under the summary receiver operating characteristic (ROC) curve was calculated to measure the accuracy of 18F-FDG PET or PET/CT in these patients.

RESULTS

Ten studies comprising 329 patients (549 scans) with MCC were included in the qualitative analysis (systematic review) and discussed. The quantitative analysis (meta-analysis) of six selected studies (including 92 patients with MCC) provided the following results on a per examination-based analysis: sensitivity was 90 % (95 % CI 80–96), specificity 98 % (95 % CI 90–100), LR+ 12 (95 % CI 4.3–33.0), LR− 0.15 (95 % CI 0.08–0.28), and DOR 86.8 (95 % CI 23–327). The area under the summary ROC curve was 0.96. No significant statistical heterogeneity between the studies was found.

CONCLUSIONS

In patients with MCC, 18F-FDG PET or PET/CT demonstrated high sensitivity and specificity, being accurate methods in this setting. Nevertheless, the literature focusing on the use of PET and PET/CT in MCC still remains limited. Prospective studies are needed to substantiate the high diagnostic accuracy of these methods in MCC.

Neuroendocrine tumours of the head and neck: anatomical, functional and molecular imaging and contemporary management

Neuroendocrine tumours (NETs) of the head and neck are rare neoplasms and can be of epithelial or non-epithelial differentiation. Although the natural history of NETs is variable, it is crucial to establish an early diagnosis of these tumours as they can be potentially curable. Conventional anatomical imaging and functional imaging using radionuclide scintigraphy and positron emission tomography/computed tomography can be complementary for the diagnosis, staging and monitoring of treatment response. This article describes and illustrates the imaging features of head and neck NETs, discusses the potential future role of novel positron-emitting tracers that are emerging into clinical practice and reviews contemporary management of these tumours. Familiarity with the choice of imaging techniques and the variety of imaging patterns and treatment options should help guide radiologists in the management of this rare but important subgroup of head and neck neoplasms.

Value of positron emission tomography/computed tomography in diagnosis and staging of primary ocular and orbital tumors

Accurate and reliable staging methods are crucial for optimal care of patients with ocular and orbital malignancies. Positron emission tomography/computed tomography (PET/CT) has recently emerged as a staging tool in the field of ophthalmic oncology. For detecting primary ocular or orbital lesions, PET/CT does not seem to provide an advantage over clinical ophthalmologic examination or conventional imaging studies such as CT or magnetic resonance imaging of the orbit. However, PET/CT may detect distant metastatic lesions that conventional imaging studies miss. For orbital and ocular adnexal lymphoma, use of PET/CT has been proven to be feasible and is now accepted both as a standard part of the initial staging work-up and for the assessment of response to therapy. For other ophthalmic tumors, PET/CT seems most appropriate for advanced metastatic tumors of the orbit, eyelid, and eye, for which the detection of distant metastasis with 1 comprehensive study may be preferable to performing multiple CT scans with contrast.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, clinically aggressive cutaneous neuroendocrine neoplasm with a high mortality rate. Though the etiology is not precisely known, Merkel cell polyomavirus DNA has been found recently in a large percentage of MCC tumors. Other suggested risk factors include sun exposure, immunosuppression, and a history of prior malignancy. Work up of patients with MCC most notably includes nodal staging via clinical examination or sentinel lymph node biopsy. The prognosis for most patients with MCC is poor, and the rarity of MCC precludes the prospective, randomized clinical trials necessary to elucidate optimum treatment protocols. Most published data support the use of a multimodality approach centered around surgical excision with negative margins, sentinel lymph node biopsy to establish the presence or absence of nodal metastases, adjuvant radiothearpy to decrease the risk of recurrence, and systemic chemotherapy in the case of widespread disease.

Imaging in patients with merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine tumor of the skin with a mortality rate of approximately 25% (Peloschek et al., 2010). Accurate assessment of nodal involvement in patients with MCC predicts significantly overall outcome (Smith et al., 2012 and Ortin-Perez et al., 2007). Due to the rarity of this highly aggressive disease, only a few imaging reports on MCC were published, and subsequently still to date no accepted imaging algorithm for MCC is available. For primary staging of MCC, general recommendations have included ultrasonography, chest X-ray CT, and MRI, but recent articles show that the use of sentinel node and FDG-PET/PET-CT is gaining more and more importance.

The predictive value of imaging studies in evaluating regional lymph node involvement in Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine malignancy with high potential for nodal or distant metastatic spread. Little information exists on sensitivity and specificity of various imaging techniques when compared with the gold standard of histopathologic evaluation of the lymph node basin.

OBJECTIVE

We sought to further understand the value of various imaging modalities in the staging and initial workup of patients with MCC.

METHODS

Of 240 patients with primary MCC evaluated between 1981 and 2008, 99 had diagnostic imaging at initial presentation with biopsy-proven cutaneous MCC and had histopathologic nodal evaluation within 4 weeks of the initial scan. We conducted a retrospective chart review of these identified patients.

RESULTS

Computed tomography (n = 69) demonstrated a sensitivity of 47%, specificity of 97%, positive predictive value of 94%, and negative predictive value of 68% in detecting nodal basin involvement. Fluorine-18-fluorodeoxyglucose positron emission tomography scan (n = 33) demonstrated a sensitivity of 83%, specificity of 95%, positive predictive value of 91%, and negative predictive value of 91% in detecting nodal basin involvement. Magnetic resonance imaging (n = 10) demonstrated a sensitivity of 0%, specificity of 86%, positive predictive value of 0%, and negative predictive value of 67% in detecting nodal basin involvement.

LIMITATIONS

This was a retrospective study with small sample size.

CONCLUSION

Use of fluorine-18-fluorodeoxyglucose positron emission tomography in the evaluation of a regional lymph node basin in primary MCC is significantly more sensitive and equally specific when compared with traditional computed tomography. Both fluorine-18-fluorodeoxyglucose positron emission tomography and computed tomography are more sensitive than clinical examination alone.

Interest of (18)F-FDG PET-CT scanning for staging and management of merkel cell carcinoma: a retrospective study of 15 patients

BACKGROUND

The additional benefit of 18FDG-Positron Emission Tomography-Computed Tomography (FDG PET-CT) compared with conventional imaging is still a controversial issue in MCC.

OBJECTIVES

This study was designed to evaluate the ability of FDG PET-CT to detect secondary lesions clinically inconspicuous and not shown by conventional imaging.

METHODS

Clinical records of 15 MCC patients were retrospectively reviewed to investigate the specific interest of FDG PET-CT compared with X-computed tomography (CT). The main endpoint was the ability of FDG PET-CT to detect secondary lesions and the possible resulting changes in disease staging and management compared with pre-FDG PET-CT data including clinical examination, sentinel lymph node biopsy (SLNB), and diagnostic CT.

RESULTS

FDG PET-CT was relevant with a single false negative result and led to significant changes in disease staging and management in 46% of patients compared with clinical examination alone. However, additional secondary lesions not detected by CT were evidenced during follow-up in a single patient with an already known metastatic disease, data which did not result in any change in staging and treatment. Sensitivity, specificity, positive predictive value and negative predictive value were respectively 0.66, 1, 1 and 0.8 for SLNB, 0.89, 1, 1 and 0.93 for CT and 0.89, 1, 1 and 0.93 for FDG PET-CT. No additional neoplasm was detected by FDG PET-CT.

CONCLUSION

Although FDG PET-CT is of questionable value in MCC management when used in parallel with CT, it may be considered as a valuable option as a single whole-body survey procedure.

Molecular imaging of neuroendocrine tumors

Neuroendocrine tumors (NET) are a heterogeneous group of tumors that arise from neuroendocrine cells. These tumors may arise from various organs, including lung, thymus, thyroid, stomach, duodenum, small bowel, large bowel, appendix, pancreas, adrenal, and skin. Most are well differentiated and have the ability to produce biogenic amines and various hormones. NET usually occur sporadically but they also be associated with various familial syndromes. For the vast majority of NET, surgical resection is the treatment of choice whenever feasible. Localization of NET prior to surgery and for staging and follow-up relies on both anatomic and functional imaging modalities. In fact, the unique secretory characteristics of these tumors lend themselves to imaging by molecular imaging modalities, which can target specific metabolic pathways or receptors. Neuroendocrine cells have a variety of such target receptors and pathways for which radiopharmaceuticals have been developed, including [(123)I/(131)I]-metaiodobenzylguanidine (MIBG), [(111)In]pentetreotide, [(68)Ga] somatostatin analogs, [(18)F] fluorodeoxyglucose (FDG), [(11)C/(18)F] dihydroxyphenylalanine (DOPA), [(11)C] 5-hydroxytryptophan (5-HTP) (99m)Tc pentavalent dimercaptosuccinic acid ([(99m)Tc] (V) DMSA, and [(18)F] fluorodopamine (FDA). Here, we review the molecular imaging approaches for NET using various radiopharmaceuticals.

The impact of (18)F-FDG PET-CT scanning for staging and management of Merkel cell carcinoma: results from Westmead Hospital, Sydney, Australia

BACKGROUND

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy with high mortality. Positron emission tomography (PET) using (18)F-fluorodeoxyglucose (FDG) has been shown to be valuable in the management of many types of cancer, and the purpose of this work was to determine its utility for patients with MCC.

OBJECTIVE

We sought to evaluate the impact of (18)F-FDG PET with simultaneous computed tomography (PET-CT) on the staging and management of patients with MCC.

METHODS

We reviewed the medical records of 18 patients with MCC who underwent 21 PET-CT scans at our institution from 2006 to 2008. The impact of PET-CT on staging and management plans were evaluated.

RESULTS

There were 12 men and 6 women with median age of 79 years (range, 54 to 85 years). All proven sites of MCC greater than 5 mm were positive on PET-CT with average maximum standardized uptake values (SUV max) of 4 in primary lesions, 5.6 in nodal disease and 11.5 in distant metastases. PET-CT contributed to altered staging in 7 patients (33%) and a change in management in 9 patients (43%). Two patients were found to have a second primary malignancy, but this did not alter management.

LIMITATIONS

This was a retrospective review. Most patients had stage II or III disease, suggesting some potential referral bias.

CONCLUSIONS

(18)F-FDG PET-CT had a high impact in the management of MCC patients in our series and this investigation merits further assessment.

Diagnostic imaging in Merkel cell carcinoma: lessons to learn from 16 cases with correlation of sonography, CT, MRI and PET

OBJECTIVE

The authors report imaging findings in a series of 16 patients with MCC, a rare tumour which is often managed primarily by a dermatologist. To our knowledge, no equivalent series of MCC has been described in the nuclear medicine literature.

MATERIAL AND METHODS

In this IRB-approved retrospective noncomparative case series 16 patients with biopsy-proven Merkel cell carcinoma were included between January 1999 and October 2007. Twenty-nine whole body PET scans (18F-FDG n=24, 18F-FDOPA n=5) in 16 patients were retrospectively reviewed with regard to tracer uptake in six anatomical sites per patient. For 127/144 of FDG-PET evaluated regions and 68/144 of regions depicted by conventional imaging methods, a valid standard of reference could be obtained. A combined standard of reference was applied, which consisted of histopathology (lymphadenectomy or biopsy) or clinical or radiological follow-up for at least 12 months.

RESULTS

the mean FDG uptake over the clinicopatholigical verified FDG avid areas was 4.7 SUV (1.5-9.9 SUV). The region based assessment of diagnostic value, in consideration of the standard of reference, resulted in a sensitivity of 85.7% and a specificity of 96.2% of FDG-PET (n=127) and in a combined sensitivity of 95.5% and a specificity of 89.1% for morphological imaging methods (n=68). Differences between methods did not reach statistical significance (p=1.00, p=0.18).

CONCLUSIONS

FDG-PET is a highly useful whole body staging method of comparable value compared to conventional imaging methods with restricted field of view. The lessons learned from case series are discussed.

A comprehensive review of the treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an uncommon but malignant cutaneous neuroendocrine carcinoma with a high incidence of local recurrence, regional lymph node metastases, and subsequent distant metastases. The etiology of MCC remains unknown. It usually occurs in sun-exposed areas in elderly people, many of whom have a history of other synchronous or metachronous sun-associated skin lesions. The outcome for most patients with MCC is generally poor. Surgery is the mainstay of treatment. The role of adjuvant therapy has been debated. However, data from recent development support a multimodality approach, including surgical excision of primary tumor with adequate margins and sentinel lymph node dissection followed by postoperative radiotherapy in most cases, as current choice of practice with better locoregional control and disease-free survival. Patients with regional nodal involvement or advanced disease should undergo nodal dissection followed by adjuvant radiotherapy and, perhaps, systemic platinum-based chemotherapy in most cases.