The diagnostic utility of the lognormal behavior of PET standardized uptake values in tumors

A meta-analysis of data primarily from PET oncologic investigations using F DG PET was performed. Its purpose was to establish statistical features of the distributions of standardized uptake values (SUVs) as possible aids in the diagnostic process. Methods: We obtained 1536 values of oncologic marke rs from patient studies of 40 investigations in the literature. Statistical parameters were tabulated for analysis. Results: A significant observation is that, unlike skewed SUV histograms, log(10)SUV has Gaussian behavior, w hich is not uncommon for biologic quantities. This was found for SUVs of FD G and 2 amino acids as well as a few other cancer markers. A possible model for explaining this is proposed. For FDG, the SD sigma of the log(10)SUVs for an average cancer category was 0.23. Examining data within the framewor k of the model points to physiologic factors as dominating SUV variability rather than PET protocols. When data for a single cancer category were avai lable from multiple institutions, averages, (SUV) over bar s, disagree beyo nd chance expectations, Diagnostic utility suggestions include a universal linear relationship between sensitivity and severity, defined as SUV/(SUV) over bar, on semilogarithmic probability paper; a generic receiver-operatin g-characteristic curve for all cancers; using [log(10)((SUV) over bar(mal)/ (SUV) over bar(norm))] divided by (sigma(mal2) + sigma(norm2))(1/2) as a si mple diagnostic effectiveness measure; and using Gaussian log(10)SUVs to av oid erroneous P values. Conclusion: Using the logarithms of markers, such a s SUVs, several advantages stemming from their Gaussian nature can be achie ved with benefits ensuing to the diagnostic process.