Page 13 - Quantitative Imaging of Small Tumours with Positron Emission Tomography
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                                Chapter 1 Imaging biomarkers have the advantage that they allow for measurements of individual lesions as well as the disease burden as a whole, which additionally allows for characterization of phenotypical heterogeneity. Commonly used imaging modalities are computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) (11,12). CT and MRI typically have high resolutions and provide detailed images of anatomical structures (11). However, anatomical data does not directly provide information on the tumour biology and/or functional processes. Also, changes in tumour size detected during treatment may occur only at a late stage, might be difficult to measure, or might partly represent non-viable tissue (13,14). PET, on the other hand, allows for non-invasive and objective in-vivo measurements of a multitude of cancer characteristics such as metabolism, functional processes, or drug targeting (12,15- 17). Prostate cancer Prostate cancer (PCa) is the most prevalent cancer type in men in the Western world, with an incidence of 12,600 new cases in the Netherlands (2018) (18). It is a heterogeneous cancer type, both biologically and clinically (19). Occurrence and progression of this disease is strongly driven by the androgen receptor (AR) (20). Clinically, it can be divided into the (early) hormone-sensitive stage and the (late and lethal) castration-resistant phase. In the hormone-sensitive stage, standard androgen deprivation by chemical or surgical castration suffices to achieve disease control. In case of disease progression despite castration levels of testosterone, the disease is deemed to be castration-resistant. In both hormone-sensitive and castrate-resistant disease, targeting the AR axis is the mainstay of treatment (21- 25). As more AR-targeted drugs are becoming available, and with the advent of metastasis-directed approaches (26), novel biomarkers for personalized treatment selection are highly needed. For this purpose, modern imaging modalities such as PET are very promising. Specifically, PET scans using tracers targeting the prostate-specific membrane antigen (PSMA) have recently revolutionized the place of functional imaging in recurrent PCa care (27). Lung cancer Lung cancer, specifically non-small cell lung cancer (NSCLC), frequently occurs in both men and women. Its incidence is rising (mainly in women), from 6800 new diagnoses in 2000 to 9300 in 2015 in the Netherlands (28). At diagnosis, half 12 


































































































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