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False positive rates in positron emission tomography (PET) voxelwise analyses.

ABSTRACT: Issues with inflated false positive rates (FPRs) in brain imaging have recently received significant attention. However, to what extent FPRs present a problem for voxelwise analyses of Positron Emission Tomography (PET) data remains unknown. In this work, we evaluate the FPR using real PET data under group assignments that should yield no significant results after correcting for multiple comparisons. We used data from 159 healthy participants, imaged with the serotonin transporter ([¹¹C]DASB; N = 100) or the 5-HT₄ receptor ([¹¹C]SB207145; N = 59). Using this null data, we estimated the FPR by performing 1,000 group analyses with randomly assigned groups of either 10 or 20, for each tracer, and corrected for multiple comparisons using parametric Monte Carlo simulations (MCZ) or non-parametric permutation testing. Our analyses show that for group sizes of 10 or 20, the FPR for both tracers was 5-99% using MCZ, much higher than the expected 5%. This was caused by a heavier-than-Gaussian spatial autocorrelation, violating the parametric assumptions. Permutation correctly controlled the FPR in all cases. In conclusion, either a conservative cluster forming threshold and high smoothing levels, or a non-parametric correction for multiple comparisons should be performed in voxelwise analyses of brain PET data.

SUBMITTER: Ganz M

PROVIDER: S-EPMC8221774 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Fluorine-18-fluoro-2-deoxy-D-glucose (FDG) is widely used as positron-emission-tomography (PET) radiotracer for the detection and staging of human cancer. Tumor uptake of FDG varies substantially between different cancer types and between patients with the same tumor type. The molecular basis for this heterogeneity is unknown. Using cancer cell lines and primary human tumors of distinct histologic origins, we here show that increased FDG uptake is universally associated with coordinate upregulation of genes within the glycolysis, pentose-phosphate, and other related metabolic pathways. In primary human breast cancers, this FDG signature shows significant overlap with established breast cancer signatures for the “basal-like” disease subtype and “poor prognosis”. FDG high breast cancer showed significantly more gene copy number alterations genome wide than FDG low cancers. About 50 % of primary breast cancers with high FDG uptake and FDG gene expression signature show DNA copy gain encompassing the c-myc gene locus and express gene sets regulated by the transcription factor MYC. Our data shows that FDG-PET marks a distinct subset of “basal-like” human breast cancer which is characterized by MYC and prognostically unfavorable gene expression signatures, suggesting that FDG-PET imaging may be useful to risk-stratify patients with locally advanced breast cancer. Our general strategy to identify molecular determinants of FDG-retention through a genome-wide approach consisted of FDG uptake measurements in cancer cell lines and primary human tumors, the selection of samples with particularly high versus low FDG-retention, and subsequent pathway-based analysis of RNA expression data collected from these samples. Cell line RNA was extracted from a 10 cm plate seeded simultaneously and at the same density as the wells for FDG-uptake assays. For primary human tumor samples, RNA was extracted from macrodissected frozen tumor tissue. All cell line RNA samples and the astrocytoma RNA aliquots were hybridized to Affymetrix U133 Plus 2.0 arrays. All primary breast cancer RNA samples were hybridized to Affymetrix U133A arrays.

Project description:Background Sunitinib is a small molecule tyrosine kinase inhibitor approved for the treatment of diverse cancers. Despite widespread clinical approval the associated cardiovascular toxicity sequelae are of concern; high grade toxicities may lead to dose reduction, interruption or discontinuation. Thus, an effective strategy for the early detection of cardiac damage in the context of sunitinib treatment is warranted. Although yet to be fully elucidated, molecular pathways and kinases implicate include those related to cardiac energy metabolism. We hypothesised that plasticity in cardiac metabolism could represent a novel early marker of cardiotoxicity. Methods and Results Female Balb/CJ mice (n = 36) or Sprague-Dawley rat (n = 12) models were treated with sunitinib. Physiological parameters were measured. An hypothesis driven cardiac positron emission tomography (PET) approach was implemented to investigate alterations in myocardial glucose, fatty acid and oxidative metabolism. Following treatment, blood pressure increased, whilst left ventricular ejection fraction decreased in both models. Increased myocardial glucose uptake after 48 hours indicated early perturbations in glucose metabolism. Myocardial fatty acid metabolism appeared increased as a result of sunitinib treatment indicated by PET but electron microscopy revealed significantly increased storage of lipids in the myocardium. Proteomic analyses indicated that oxidative metabolism, fatty acid β-oxidation and mitochondrial dysfunction were among the top cardiac signalling pathways perturbed by sunitinib treatment. [11C]Acetate-PET data suggested a decrease in myocardial perfusion following 5 days of treatment. Conclusions Data implicates sunitinib as a mediator of compromised myocardial energy metabolism. Increased reliance on glycolysis, increases in myocardial lipid deposition and perturbed mitochondrial function may ultimately result in a fundamental energy crisis manifesting as compromised cardiac function, the long term effects of which are unknown. Our data support the utility of an hypothesis driven PET approach to monitor cardiac metabolic pathway remodelling in response to sunitinib, which may ultimately have clinical utility as a novel safety imaging biomarker strategy.

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False positive rates in positron emission tomography (PET) voxelwise analyses.

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