Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Vehabovic-Delic, A.
Volume CT Perfusion (VCTP) Imaging in Evaluation of the Significance in Oncologic Follow-up: Imaging of Metastasizing RCC - Comparison between changes in Perfusion and Changes in Size in the early period of targeted therapy.
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2020. pp. 89
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Balic Marija
- Deutschmann Hannes
- Schoellnast Helmut
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- Abstract:
- Introduction: Since 2004 when first antiangiogenic agent was approved for the treatment of colorectal cancer, oncologic treatment in many solid tumors has changed. Main targets for oncologic therapy have been switched from heterogeneous proliferating tumor cells to more homogenous tumor vasculature targeted by antiangiogenic agents. Because of different mechanism of action and due to different pattern of treatment response at imaging during follow-up, a current challenge is to find appropriate surrogate biomarkers of the tumor vasculature for appropriate follow up of tumor response to antiangiogenic treatment. Recent work has led to development of non-invasive quantitative dynamic imaging techniques, such as CT perfusion (CTP) that assess early changes in tumor angiogenesis, therewith tumor physiology. The aim of this thesis was to analyze whether volume CT perfusion (VCTP) imaging of tumors treated with targeted therapy may allow for earlier response assessment than conventional CT imaging with size measurements. An additional aim was to analyze, whether there was any evidence of association between perfusion parameters and clinical outcome. Material and Methods: VCTP imaging was performed in ten patients with histologically verified metastasizing renal cell carcinoma (RCC) before and one month after initiation of targeted therapy using a 320-slice Volume CT scanner. Blood flow (BF), blood volume (BV) and clearance (CL) were calculated for both time points using compartmental analysis algorithms. In addition, the longest tumor diameter (LD) was measured. Perfusion parameters and LD before and after treatment were compared, and their relative change was correlated against disease progression time (TTP) and associated to tumor response. Results: For patients who responded to therapy, perfusion parameters have significantly decreased; BF by -37.5%, BV by -28.9% and CL by -50.8% on average. Decrease in tumor size was -9.4%. For non-responders, change in perfusion parameters was inconsistent. Overview of individual cases showed that relative change of BV was the most important perfusion parameter, with highest difference between responders and non-responders (90%). Other parameters increased specificity of perfusion imaging. The most valuable predictor of TTP for patients who responded to therapy was the relative change of BF, with lowest relative deviation from true value of TTP, confirmed by multiple linear regression analysis. Conclusion: In the early period after targeted therapy VCTP may be able to discriminate responders from non-responders, sooner than the currently used changes in tumor size. Different percentage change of all three parameters indicated that the therapy has probably affected the physiological processes of angiogenesis in varying degrees and, therefore, all perfusion parameters may have to be considered independently of one another. A decrease of all three perfusion parameters, no matter on percentage change, may be interpreted as positive response to antiangiogenic therapy. Relative change of BV was the most important parameter for detection of non-responders, whereas use of other parameters increased the CTP specificity. In addition, relative change of BF may be a promising parameter for prediction of TTP.