Table 1.
Summary of the published studies (including >1 patient) on positron emission tomography (PET) in Merkel cell carcinoma (in chronological order).
| Author (Year) | Study Design | No. of Patients (Mean Age; % Male) | PET Radiotracers | Main Findings |
|---|---|---|---|---|
| Scanga et al. (2004) [14] | Retrospective | 2 (n.r.) | 18F-FDG | 1 TP patient, 1 TN patient |
| Yao et al. (2005) [15] | Report of 2 cases | 2 (68 years; 100%) | 18F-FDG | Pre-treatment PET scans revealed metastatic disease not detected in CT. Post-treatment PET imaging predicted response to therapy. |
| Talbot et al. (2005) [16] | Case series | 3 (63 years; 67%) |
18F-FDOPA 18F-FDG |
2 TP cases with both 18F-FDOPA and 18F-FDG. No uptake of 18F-FDOPA, and unclear findings with 18F-FDG in the TN patient. Lower image contrast with 18F-FDOPA compared to 18F-FDG. |
| Belhocine et al. (2006) [17] | Retrospective | 11 (64 years; 36%) | 18F-FDG | Sensitivity 92% (11 TP, 1 FN), specificity 100% (3 TN, 0 FP). Contributive PET findings in 10/11 MCC cases. |
| Iagaru et al. (2006) [18] | Retrospective case series | 6 (69 years; 67%) | 18F-FDG | 9 TP, 7 TN, 1 FP, and 1 FN lesions. |
| Concannon et al. (2009) [19] | Retrospective | 18 (74 years; 67%) | 18F-FDG | PET/CT altered staging in 33% and management in 43% of cases. Sensitivity 94%. |
| Peloschek et al. (2010) [20] | Retrospective | 16 (75 years; 69%) |
18F-FDG (16 pts.) 18F-FDOPA (5 pts) |
18F-FDG: Sensitivity 85.7%, specificity 96.2% 18F-FDOPA: Negative findings in all cases (19 TN, 2 FN). |
| Maury et al. (2011) [21] | Retrospective | 15 (68 years; 60%) | 18F-FDG | PET/CT had significant impact on staging and management in 46% of cases vs. clinical examination alone. Sensitivity, specificity, PPV, and NPV were 89%, 100%, 100%, and 93%, respectively. |
| Lu et al. (2012) [22] | Retrospective | 9 (70 years; 78%) | 18F-FDG | 18F-FDG PET/CT detected more lesions and staged patients more accurately than 111In-Pentetreotide scintigraphy. 6 TP, and 4 TN scans. |
| Colgan et al. (2012) [23] | Retrospective | 33 (70 years; 72%) * | 18F-FDG | Sensitivity 83%, specificity 95%, PPV 91%, NPV 91% in detecting nodal basin disease. |
| Hawryluk et al. (2012) [24] | Retrospective | 97 (70 years; 58%) | 18F-FDG | PET/CT detected regional nodal disease in 14% of patients, and upstaged 16% of more advanced cases. |
| Schmidt et al. (2012) [25] | Report of 2 cases | 2 (72 years; 50%) | 68Ga-DOTATATE | Disease extent was determined in both cases leading to management changes with inclusion of DOTATATE-peptide receptor radiotherapy in the therapeutic regimen. |
| Siva et al. (2013) [26] | Retrospective | 102 (77 years; n.r.) | 18F-FDG | PET-based staging had a significant impact on management in 37% of cases. High- and medium-impact scans were recorded for 22% and 15% of patients, respectively. PET staging results differed from conventional staging results in 22% of patients. In stratification by PET-defined stage, the 5-year OS was 67% in stage I/II patients and 31% in stage III cases (log-rank p < 0.001). On multivariate analysis, PET staging was significantly associated with OS (p < 0.001). |
| Ibrahim et al. (2013) [27] | Retrospective | 20 (58 years; 45%) | 18F-FDG | Changes in tumor status and management occurred in 20% and 15% of cases, respectively, as a direct result of PET/CT. |
| George et al. (2014) [28] | Retrospective | 23 (74 years #; 57%) | 18F-FDG | Sensitivity 97%, specificity 89%, PPV 94%, NPV 94%, with 2 FP and 1 FN results. Lesions neglected clinically or by conventional imaging were revealed in 44% of PET/CTs at initial presentation and during follow-up, with, respectively, 50% and 41% of scans identifying new lesions. At initial presentation, PET/CT altered tumor staging in 39% of cases. Management was modified by PET/CT in one-third of cases (33% at initial presentation; 32% during follow-up; 36% during evaluation of chemotherapy response). |
| Buder et al. (2014) [29] | Retrospective | 24 (68 years; 67%) |
68Ga-DOTATOC 68Ga-DOTATATE |
Sensitivity 73% for nodal, 100% for bone, and 67% for soft-tissue metastases. Up-staging and management changes in 17% and 13% of cases, respectively, as a result of PET. |
| Byrne et al. (2015) [30] | Retrospective | 62 (n.r.) | 18F-FDG | The impact of PET on disease restaging was high in 45% and medium in 11% of cases, respectively. Patients who achieved no CMR had a 15% 1-year OS, while those with CMR had an 88% 2-year and a 68% 5-year OS. Both CMR achievement and nodal disease were significantly prognostic of the OS. |
| Sollini et al. (2015) [31] | Retrospective | 23 (70 years; 78%) |
68Ga-DOTATOC 68Ga-DOTANOC 68Ga-DOTATATE |
11 TP, 8 TN, 3 FP, and 1 FN cases. Sensitivity 92%, specificity 73%, and diagnostic accuracy 83%. Impact on management in 30% of cases. |
| Ben-Haim et al. (2016) [32] | Retrospective | 46 (68 years; 61%) | 18F-FDG | PET/CT altered disease stage in 26% resulting in management changes in 15% of cases. |
| Liu et al. (2017) [33] | Retrospective | 16 (69 years; 75%) | 18F-FDG | In stage I-II MCC, PET/CT was less sensitive (6% positive results) vs. SLNB (63% positive results) in detecting occult nodal metastasis. |
| Poulsen et al. (2017) [34] | Prospective | 58 (68 years; 78%) | 18F-FDG | Sensitivity 95%, specificity 88%, PPV 95%, NPV 88%. Pre-treatment PET impacted treatment decisions in 27.6% of cases, leading to upstaging in 25.9% of them. |
| Taralli et al. (2018) [35] | Retrospective | 15 (70 years; 80%) |
18F-FDG 68Ga-DOTATOC 68Ga-DOTANOC 68Ga-DOTATATE |
On patient-based analysis, 18F-FDG and 68Ga-somatostatin analogs showed both 100% sensitivity, and 85.7% and 71.4% specificity, respectively, without significant difference. On lesion-based analysis, 18F-FDG detected 89% and 68Ga-somatostatin analogs 92% of the lesions, without significant difference. |
| Singh et al. (2020) [10] | Retrospective | 352 (nr.; nr.) | 18F-FDG | PET/CT upstaged 16.8% of patients. Higher sensitivity vs. CT. Baseline imaging led to upstaging also in patients with clinically uninvolved regional nodes. |
TP, true positive; TN, true negative; FP, false positive; FN, false negative; PPV, positive predictive value; NPV, negative predictive value; OS, overall survival; SLNB, sentinel lymph node biopsy; MCC, Merkel cell carcinoma; CMR, complete metabolic response; n.r., not reported. * The numbers refer to the whole study population of 99 patients. # Median age (mean age not provided).