Evaluation of 18F-FDG PET and MRI in differentiating benign and malignant peripheral nerve sheath tumors

Abstract Purpose Detecting malignant peripheral nerve sheath tumors (MPNSTs) remains difficult. 18F-FDG PET-CT has been shown helpful, but ideal threshold values of semi-quantitative markers remain unclear, partially because of variation among scanners. Using EU-certified scanners diagnostic accuracy of ideal and commonly used 18F-FDG PET-CT thresholds were investigated and differences between adult and pediatric lesions were evaluated. Methods A retrospective cohort study was performed including patients from two hospitals with a clinical or radiological suspicion of MPNST between 2013 and 2019. Several markers were studied for ideal threshold values and differences among adults and children. A diagnostic algorithm was subsequently developed. Results Sixty patients were included (10 MPNSTs). Ideal threshold values were 5.8 for SUVmax (sensitivity 0.70, specificity 0.92), 5.0 for SUVpeak (sensitivity 0.70, specificity 0.97), 1.7 for TLmax (sensitivity 0.90, specificity 0.86), and 2.3 for TLmean (sensitivity 0.90, specificity 0.79). The standard TLmean threshold value of 2.0 yielded a sensitivity of 0.90 and specificity of 0.74, while the standard SUVmax threshold value of 3.5 yielded a sensitivity of 0.80 and specificity of 0.63. SUVmax and adjusted SUV for lean body mass (SUL) were lower in children, but tumor-to-liver ratios were similar in adult and pediatric lesions. Using TLmean > 2.0 or TLmean < 2.0 and SUVmax > 3.5, a sensitivity and specificity of 1.00 and 0.63 can be achieved. Conclusion 18F-FDG PET-CT offers adequate accuracy to detect MPNSTs. SUV values in pediatric MPNSTs may be lower, but tumor-to-liver ratios are not. By combining TLmean and SUVmax values, a 100% sensitivity can be achieved with acceptable specificity.

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A Bayesian approach for diagnostic accuracy of malignant peripheral nerve sheath tumors: a systematic review and meta-analysis

Neuro-Oncology ◽

10.1093/neuonc/noaa280 ◽

2020 ◽

Author(s):

Enrico Martin ◽

Ritchie T J Geitenbeek ◽

J Henk Coert ◽

David F Hanff ◽

Laura H Graven ◽

...

Keyword(s):

Peripheral Nerve ◽

Diagnostic Accuracy ◽

Fdg Pet ◽

Nerve Sheath Tumors ◽

Peripheral Nerve Sheath Tumors ◽

Target Sign ◽

Perilesional Edema ◽

Nerve Sheath ◽

Dismal Prognosis ◽

Meta Analyses

Abstract Background Malignant peripheral nerve sheath tumors (MPNST) carry a dismal prognosis and require early detection and complete resection. However, MPNSTs are prone to sampling errors and biopsies or resections are cumbersome and possibly damaging in benign PNST (BPNST). This study aimed to systematically review and quantify diagnostic accuracy of non-invasive tests for distinguishing MPNST from BPNST. Methods Studies on accuracy of MRI, FDG-PET, and liquid biopsies were identified in PubMed and Embase from 2000-2019. Pooled accuracies were calculated using Bayesian bivariate meta-analyses. Individual level-patient data was analyzed for ideal maximum standardized uptake volume (SUVmax) threshold on FDG-PET. Results Forty-three studies were selected for qualitative synthesis including data on 1875 patients and 2939 lesions. Thirty-five studies were included for meta-analyses. For MRI, absence of target sign showed highest sensitivity (0.99, 95% CI: 0.94-1.00); ill-defined margins (0.94, 95% CI: 0.88-0.98) and perilesional edema (0.95, 95% CI: 0.83-1.00) showed highest specificity. For FDG-PET, SUVmax and tumor-to-liver ratio show similar accuracy; sensitivity 0.94, 95% CI: 0.91-0.97 and 0.93, 95% CI: 0.87-0.97 respectively, specificity 0.81, 95% CI: 0.76-0.87 and 0.79, 95% CI: 0.70-0.86 respectively. SUVmax ≥3.5 yielded the best accuracy with a sensitivity of 0.99 (95% CI: 0.93-1.00) and specificity of 0.75 (95% CI: 0.56-0.90). Conclusions Biopsies may be omitted in the presence of a target sign and the absence of ill-defined margins or perilesional edema. Because of diverse radiological characteristics of MPNST, biopsies may still commonly be required. In Neurofibromatosis type 1, FDG-PET scans may further reduce biopsies. Ideal SUVmax threshold is ≥3.5.

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