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Serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine PET for monitoring the effects of intracavitary radioimmunotherapy in patients with malignant glioma.

ABSTRACT: PURPOSE: Intracavitary radioimmunotherapy (RIT) offers an effective adjuvant therapeutic approach in patients with malignant gliomas. Since differentiation between recurrence and reactive changes following RIT has a critical impact on patient management, the aim of this study was to analyse the value of serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine (FET) PET scans in monitoring the effects of this locoregional treatment. METHODS: Following conventional therapy, 24 glioma patients (5 WHO III, 19 WHO IV) underwent one to five RIT cycles with either (131)I-labelled (n=19) or (188)Re-labelled (n=5) anti-tenascin antibodies. Patients were monitored with serial FET PET scans (2-12 scans). For semiquantitative evaluation, maximal tumoural uptake (TU(max)) was evaluated and the ratio to background (BG) was calculated. Results of PET were correlated with histopathological findings (n=9) and long-term clinical follow-up for up to 87 months. RESULTS: In seven tumour-free patients, PET revealed slightly increasing but homogeneous FET uptake surrounding the resection cavity with a peak up to 18 months following RIT (TU(max)/BG 2.07+/-0.25) but stable or decreasing values during further follow-up (last follow-up: TU(max)/BG 1.63+/-0.22). Seventeen patients developed regrowth of residual tumour/tumour recurrence showing additional nodular FET uptake (TU(max)/BG 2.79+/-0.53). A threshold value of 2.4 (TU(max)/BG) allowed best differentiation between recurrence and reactive changes (sensitivity 82%, specificity 100%). CONCLUSION: FET PET is a sensitive tool for monitoring the effects of locoregional RIT. Homogeneous, slightly increasing FET uptake around the tumour cavity with a peak up to 18 months after RIT, followed by stable or decreasing uptake, points to benign, therapy-related changes. In contrast, nodular uptake is a reliable indicator of recurrence.

SUBMITTER: Popperl G

PROVIDER: S-EPMC1998889 | biostudies-other | 2006 Jul

REPOSITORIES: biostudies-other

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Project description:Immune checkpoint inhibitors (ICIs) are now commonly used to treat patients with metastatic malignant melanoma. Although concerns have been raised that the inflammatory response induced by ICIs may limit the ability of 18F-FDG PET/CT to assess tumor response, systematic analyses on the use of 18F-FDG PET/CT in this setting are mostly lacking. Thus, we set out to evaluate the association between tumor response on 18F-FDG PET/CT and prognosis in patients with metastatic malignant melanoma treated with ipilimumab. Methods: We analyzed 60 consecutive patients with metastatic melanoma who underwent 18F-FDG PET/CT scans both before and after treatment to evaluate treatment response after completion of ipilimumab therapy. Tumor response was assessed by the change in the sum of SULpeak (voxels with the highest average SUL [SUV normalized to lean body mass]) of up to 5 lesions according to PERCIST5. New lesions on PET that appeared suggestive of metastases were considered progressive metabolic disease (PMD). Because immunotherapy may cause new inflammatory lesions that are detectable on 18F-FDG PET/CT, we also evaluated an immunotherapy-modified response classification (imPERCIST5). In this classification, new lesions do not define PMD per se; rather, PMD requires an increase in the sum of SULpeak by 30%. The correlation between tumor response according to these 3 definitions and overall survival (OS) was evaluated and compared with known prognostic factors. Results: In responders and nonresponders, the 2-y OS was 66% versus 29% for imPERCIST5 (P = 0.003). After multivariate analysis, imPERCIST5 remained prognostic (hazard ratio, 3.853; 95% confidence interval, 1.498-9.911; P = 0.005). New sites of focal 18F-FDG uptake occurred more often in patients with PMD (n = 24) by imPERCIST5 than in those with stable metabolic disease (n = 7) or partial metabolic response (n = 4). In patients with partial metabolic response, 2 of 4 isolated new lesions regressed spontaneously during follow-up. Conclusion: In patients with metastatic melanoma treated with ipilimumab, tumor response according to PERCIST was associated with OS. Our data suggest that PMD should not be defined by the appearance of new lesions, but rather by an increase in the sum of SULpeak.

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Serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine PET for monitoring the effects of intracavitary radioimmunotherapy in patients with malignant glioma.

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