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    Sjoukje Oosting

    Patients with von Hippel-Lindau disease (VHL) are at risk to develop multiple tumors. The growth of lesions is unpredictable and regular surveillance is critical for early treatment to control local damage. Vascular endothelial growth... more
    Patients with von Hippel-Lindau disease (VHL) are at risk to develop multiple tumors. The growth of lesions is unpredictable and regular surveillance is critical for early treatment to control local damage. Vascular endothelial growth factor (VEGF)-A produced locally is supposed to play an important role in development of disease manifestations and is a target for antiangiogenic therapy with the monoclonal antibody bevacizumab. We aimed to assess whether VHL manifestations can be visualized with 89Zirconium-bevacizumab positron emission tomography ((89)Zr-bevacizumab PET) and to explore whether (89)Zr-bevacizumab PET can differentiate progressive from non-progressive lesions. VHL patients with at least one measurable hemangioblastoma were eligible. An intravenous injection with 37MBq (89)Zr-bevacizumab was administered 4 days before the scan. Maximum standardized uptake values were calculated. PET-scans were fused with routine magnetic resonance imaging (MRI) of the central nervous ...
    No validated predictive biomarkers for antiangiogenic treatment of metastatic renal cell carcinoma (mRCC) exist. Tumor vascular endothelial growth factor A (VEGF-A) level may be useful. We determined tumor uptake of (89)Zr-bevacizumab, a... more
    No validated predictive biomarkers for antiangiogenic treatment of metastatic renal cell carcinoma (mRCC) exist. Tumor vascular endothelial growth factor A (VEGF-A) level may be useful. We determined tumor uptake of (89)Zr-bevacizumab, a VEGF-A-binding PET tracer, in mRCC patients before and during antiangiogenic treatment in a pilot study. Patients underwent (89)Zr-bevacizumab PET scans at baseline and 2 and 6 wk after initiating either bevacizumab (10 mg/kg every 2 wk) with interferon-α (3-9 million IU 3 times/wk) (n = 11) or sunitinib (50 mg daily, 4 of every 6 wk) (n = 11). Standardized uptake values were compared with plasma VEGF-A and time to disease progression. (89)Zr-bevacizumab PET scans visualized 125 evaluable tumor lesions in 22 patients, with a median SUV(max) (maximum standardized uptake value) of 6.9 (range, 2.3-46.9). Bevacizumab/interferon-α induced a mean change in tumor SUV(max) of -47.0% (range, -84.7 to +20.0%; P < 0.0001) at 2 wk and an additional -9.7% (ra...
    Testicular carcinoma is a rare tumour but the most frequently occurring form of cancer in men aged 18-35 years. In metastatic disease, following orchidectomy three or four courses of combination chemotherapy with cisplatin are given. With... more
    Testicular carcinoma is a rare tumour but the most frequently occurring form of cancer in men aged 18-35 years. In metastatic disease, following orchidectomy three or four courses of combination chemotherapy with cisplatin are given. With a general chance of cure of 80-90%, testicular cancer is still regarded as a model for a form of cancer that is curable. Due to this favourable prognosis--and to its rising incidence--the group of people who survive testicular cancer is growing and more attention is being paid to the risk of adverse consequences of treatment: secondary tumours and cardiovascular morbidity. Shared care follow-up for testicular cancer survivors with participation of both primary and secondary care is currently developed.
    Non-invasive imaging of angiogenesis could ease the optimization of antiangiogenesis treatments for cancer. In this study, we evaluated the role of VEGF-PET as a biomarker of dynamic angiogenic changes in tumors following treatment with... more
    Non-invasive imaging of angiogenesis could ease the optimization of antiangiogenesis treatments for cancer. In this study, we evaluated the role of VEGF-PET as a biomarker of dynamic angiogenic changes in tumors following treatment with the kinase inhibitor sunitinib. The effects of sunitinib treatment and withdrawal on the tumor was investigated using the new VEGF-PET tracer (89)Zr-ranibizumab as well as (18)F-FDG PET, and (15)O-water PET in mouse xenograft models of human cancer. The obtained imaging results were compared with tumor growth, VEGF plasma levels and immunohistologic analyzes. In contrast to (18)F-FDG and (15)O-water PET, VEGF-PET demonstrated dynamic changes during sunitinib treatment within the tumor with a strong decline in signal in the tumor center and only minimal reduction in tumor rim, with a pronounced rebound after sunitinib discontinuation. VEGF-PET results corresponded with tumor growth and immunohistochemical vascular- and tumor- markers. Our findings highlight the strengths of VEGF-PET imaging to allow serial analysis of angiogenic changes in different areas within a tumor.
    Audit and feedback on professional practice and health care outcomes are the most often used interventions to change behaviour of professionals and improve quality of health care. However, limited information is available regarding... more
    Audit and feedback on professional practice and health care outcomes are the most often used interventions to change behaviour of professionals and improve quality of health care. However, limited information is available regarding preferred feedback for patients, professionals and health insurers. Investigate the (differences in) preferences of receiving feedback between stakeholders, using the Dutch Head and Neck Audit as an example. A total of 37 patients, medical specialists, allied health professionals and health insurers were interviewed using semi-structured interviews. Questions focussed on: "Why," "On what aspects" and "How" do you prefer to receive feedback on professional practice and health care outcomes? All stakeholders mentioned that feedback can improve health care by creating awareness, enabling self-reflection and reflection on peers or colleagues, and by benchmarking to others. Patients prefer feedback on the actual professional pract...
    We sought to assess the effect of age on overall survival (OS), cancer-specific survival (CSS), and non-cancer-related death (NCRD) in elderly (aged ≥70 years) head and neck squamous cell carcinoma (HNSCC) patients treated with definitive... more
    We sought to assess the effect of age on overall survival (OS), cancer-specific survival (CSS), and non-cancer-related death (NCRD) in elderly (aged ≥70 years) head and neck squamous cell carcinoma (HNSCC) patients treated with definitive radiation therapy. The results were compared with those of younger patients, and the most important prognostic factors for survival endpoints were determined. Treatments may be better justified based on identification of the main differences in survival between young and elderly patients. Data were analyzed from all consecutive HNSCC patients treated with definitive radiation therapy (66-70 Gy) in our department between April 2007 and December 2014. A total of 674 patients, including 168 elderly patients (24.9%), were included in the study. Multivariate association models were constructed to assess the effect of age on survival endpoints. Multivariate analysis was performed to identify potential prognostic factors for survival in elderly patients. ...
    Currently, biomarkers that predict efficacy of everolimus in metastatic renal cell carcinoma (mRCC) patients are lacking. Everolimus inhibits vascular endothelial growth factor A (VEGF-A) expression. We performed PET scans in mRCC... more
    Currently, biomarkers that predict efficacy of everolimus in metastatic renal cell carcinoma (mRCC) patients are lacking. Everolimus inhibits vascular endothelial growth factor A (VEGF-A) expression. We performed PET scans in mRCC patients with (89)Zr-bevacizumab, a VEGF-A-binding antibody tracer. Aims were to determine change in tumor tracer uptake after start of everolimus and to explore if (89)Zr-bevacizumab PET can identify patients with early disease progression. (89)Zr-bevacizumab PET was done before and 2 and 6 weeks after start of everolimus 10 mg/day in mRCC patients. Routine CT scans were performed at baseline and every 3 months thereafter. Tumor tracer uptake was quantified using maximum Standardized Uptake Value (SUVmax). Endpoints were change in tumor tracer uptake and treatment response on CT after 3 months. Thirteen patients participated. Median SUVmax of 94 tumor lesions was 7.3 (range 1.6-59.5). Between patients, median tumor SUVmax varied up to 8-fold. After 2 weeks, median SUVmax was 6.3 (1.7-62.3) corresponding to a mean decrease of 9.1% (P < 0.0001). Three patients discontinued everolimus early. At 6 weeks, a mean decrease in SUVmax of 23.4% compared to baseline was found in 70 evaluable lesions of 10 patients, with a median SUVmax of 5.4 (1.1-49.4, P < 0.0001). All 10 patients who continued treatment had stable disease at 3 months. Everolimus decreases (89)Zr-bevacizumab tumor uptake. Further studies are warranted to evaluate predictive value of (89)Zr-bevacizumab PET for everolimus antitumor efficacy.
    There is an ongoing debate about the value of (neo-)adjuvant chemotherapy in high- and intermediate-grade osteosarcoma of the head and neck. All records of patients older than 16 years diagnosed with osteosarcoma of the head and neck in... more
    There is an ongoing debate about the value of (neo-)adjuvant chemotherapy in high- and intermediate-grade osteosarcoma of the head and neck. All records of patients older than 16 years diagnosed with osteosarcoma of the head and neck in the Netherlands between 1993 and 2013 were reviewed. We identified a total of 77 patients with an osteosarcoma of the head and neck; the 5-year overall survival (OS) was 55%. In 50 patients with surgically resected high- or intermediate-grade osteosarcoma of the head and neck younger than 75 years, univariate and multivariable analysis, adjusting for age and resection margins, showed that patients who had not received chemotherapy had a significantly higher risk of local recurrence (hazard ratio [HR] = 3.78 and 3.66, respectively). In patients younger than 75 years of age with surgically resected high- and intermediate-grade osteosarcoma of the head and neck, treatment with (neo-)adjuvant chemotherapy resulted in a significantly smaller risk of local...
    To compare cumulative cisplatin dose and toxicity between patients who received 3-weekly versus weekly cisplatin during adjuvant radiotherapy for high-risk head and neck squamous cell carcinoma (HNSCC). Consecutive HNSCC patients with... more
    To compare cumulative cisplatin dose and toxicity between patients who received 3-weekly versus weekly cisplatin during adjuvant radiotherapy for high-risk head and neck squamous cell carcinoma (HNSCC). Consecutive HNSCC patients with involved resection margins and/or extra-capsular extension in two tertiary cancer centers with different institutional practices were identified. Cumulative cisplatin dose was calculated and information on toxicity reviewed and compared between patients who received 3-weekly versus weekly cisplatin. Of 270 high risk patients, 60 received 3-weekly 100mg/m(2) and 48 received weekly 50mg/m(2) cisplatin during adjuvant radiotherapy (60-66Gy in 30-33 fractions). Fourteen patients received other chemotherapy schedules and 148 received no chemotherapy. Mean cumulative cisplatin dose was 199.4mg/m(2) (standard error (SE) 5.4) in 3-weekly versus 239.8mg/m(2) (SE 11.0, P=0.001) in weekly treated patients. Cumulative cisplatin ⩾200mg/m(2) was given to 67.7% of pa...
    In metastatic testicular cancer patients treated with bleomycin, etoposide, and cisplatin (BEP) chemotherapy, bleomycin-induced pneumonitis is a well-known and potentially fatal side effect. We sought to determine the prevalence of... more
    In metastatic testicular cancer patients treated with bleomycin, etoposide, and cisplatin (BEP) chemotherapy, bleomycin-induced pneumonitis is a well-known and potentially fatal side effect. We sought to determine the prevalence of lesions as signs of bleomycin-induced pulmonary changes on restaging computed tomography (CT) scans after treatment and to ascertain whether fibrosis markers were predictive of these changes. This prospective nonrandomized cohort study included metastatic testicular cancer patients, 18-50 years of age, treated with BEP chemotherapy. Restaging CT scans were examined for lesions as signs of bleomycin-induced pulmonary changes by two independent radiologists and graded as minor, moderate, or severe. Plasma samples were collected before, during, and after treatment and were quantified for transforming growth factor-β1 (TGF-β1), growth differentiation factor-15 (GDF-15), and high-sensitivity C-reactive protein (hs-CRP). In total, 66 patients were included: For...
    Patients with von Hippel-Lindau disease (VHL) are at risk to develop multiple tumors. The growth of lesions is unpredictable and regular surveillance is critical for early treatment to control local damage. Vascular endothelial growth... more
    Patients with von Hippel-Lindau disease (VHL) are at risk to develop multiple tumors. The growth of lesions is unpredictable and regular surveillance is critical for early treatment to control local damage. Vascular endothelial growth factor (VEGF)-A produced locally is supposed to play an important role in development of disease manifestations and is a target for antiangiogenic therapy with the monoclonal antibody bevacizumab. We aimed to assess whether VHL manifestations can be visualized with 89Zirconium-bevacizumab positron emission tomography ((89)Zr-bevacizumab PET) and to explore whether (89)Zr-bevacizumab PET can differentiate progressive from non-progressive lesions. VHL patients with at least one measurable hemangioblastoma were eligible. An intravenous injection with 37MBq (89)Zr-bevacizumab was administered 4 days before the scan. Maximum standardized uptake values were calculated. PET-scans were fused with routine magnetic resonance imaging (MRI) of the central nervous ...
    Central nervous system hemangioblastomas occur sporadically and in patients with von Hippel-Lindau (VHL) disease due to a VHL germline mutation. This mutation leads to enhanced transcription of chemokine receptor 4 (CXCR4), its ligand... more
    Central nervous system hemangioblastomas occur sporadically and in patients with von Hippel-Lindau (VHL) disease due to a VHL germline mutation. This mutation leads to enhanced transcription of chemokine receptor 4 (CXCR4), its ligand (CXCL12) and vascular endothelial growth factor A (VEGFA). We aimed to determine in VHL-related and sporadic hemangioblastomas CXCR4, CXCL12, and VEGFA protein expression and to correlate this to hemangioblastoma size and expression in normal surrounding tissue. 27 patients with a hemangioblastoma were included for analysis of immunohistochemistry of tissue, MRI and DNA. Hemangioblastomas overexpress CXCR4, CXCL12, and VEGFA compared to normal surrounding tissue. In sporadic hemangioblastomas the mean percentage of CXCR4 positive hemangioblastoma cells was 16 %, SD 8.4, in VHL-related hemangioblastomas 8 %, SD 4.4 (P = 0.002). There was no relation between preoperative tumor size and CXCR4 or CXCL12 expression. Compared to normal surrounding tissue CXC...
    Vascular endothelial growth factor (VEGF) pathway targeting agents have been combined with other anticancer drugs, leading to improved efficacy in carcinoma of the cervix, stomach, lung, colon and rectum, ovary, and breast. Vessel... more
    Vascular endothelial growth factor (VEGF) pathway targeting agents have been combined with other anticancer drugs, leading to improved efficacy in carcinoma of the cervix, stomach, lung, colon and rectum, ovary, and breast. Vessel normalization induced by VEGF pathway targeting agents influences tumor drug uptake. Following bevacizumab treatment, preclinical and clinical studies have shown a decrease in tumor delivery of radiolabeled antibodies and two chemotherapeutic drugs. The decrease in vessel pore size during vessel normalization might explain the decrease in tumor drug uptake. Moreover, the addition of bevacizumab to cetuximab, or panitumumab in colorectal cancer patients or to trastuzumab in breast cancer patients, did not improve efficacy. However, combining bevacizumab with chemotherapy did increase efficacy in some cancer types. Novel biomarkers to select patients who may benefit from combination therapies, such as the effect of an angiogenesis inhibitor on tumor perfusio...
    The aim of this study was to clinically validate a multivariable normal tissue complication probability (NTCP) model for grade 2-4 swallowing dysfunction at 6months after radiotherapy or chemoradiation (SWALM6) in head and neck cancer... more
    The aim of this study was to clinically validate a multivariable normal tissue complication probability (NTCP) model for grade 2-4 swallowing dysfunction at 6months after radiotherapy or chemoradiation (SWALM6) in head and neck cancer patients treated with swallowing sparing intensity modulated radiotherapy (SW-IMRT) and to test if SW-IMRT resulted in a reduction of the prevalence of SWALM6. The primary endpoint was SWALM6. For all 186 patients, a standard IMRT (parotid sparing) and a SW-IMRT plan (additional constraints for swallowing organs at risk) was created. The difference in NTCP for SWALM6 (ΔNTCPSWALM6=NTCPstandard-NTCPSW-IMRT) was calculated. Patients were treated with SW-IMRT. The external validation of the NTCP model was analyzed by comparing performance measures. The mean ΔNTCPSWALM6 was 4.9% (range 0.01-17.3%), with a significant lower mean predicted NTCPSW-IMRT of 22.6% (95% CI 20.2-24.9%), compared to NTCPstandard of 27.5% (95% CI 24.9-29.9%) (p<0.001). There was a...
    Patients with elevated human chorionic gonadotrophin (HCG) can have hyperthyroidism. We assessed the prevalence of hyperthyroidism in patients presenting with disseminated non-seminomatous germ-cell tumors (NSGCT). In all patients with... more
    Patients with elevated human chorionic gonadotrophin (HCG) can have hyperthyroidism. We assessed the prevalence of hyperthyroidism in patients presenting with disseminated non-seminomatous germ-cell tumors (NSGCT). In all patients with metastatic NSGCT who started chemotherapy at our center from April 2001 to April 2007, thyroid function was analyzed. The association between thyroid function and HCG level was examined and the frequency of hyperthyroidism in patients with low (<5000 IU/l), intermediate (> or = 5000 but <50 000 IU/l) and high (> or = 50 000 IU/l) serum HCG was assessed. For 144 of 148 eligible patients, thyroid function tests were available. Five patients with hyperthyroidism (3.5%) were identified, who all had high-serum HCG (mean 1 325 147 IU/l). Fifty percent of the patients with high HCG levels had hyperthyroidism versus 0% of the patients with HCG <50 000 IU/l (P < 0.001). Free thyroxin levels normalized within 26 days after starting chemotherapy in all patients. Hyperthyroidism frequently accompanies NSGCT with highly elevated HCG. Since its symptoms overlap with those of extensive metastatic disease, it may not be recognized. Thyroid function should be assessed in patients with high HCG levels and symptomatic hyperthyroidism should be treated temporarily with beta-blockade or antithyroidal medication.
    To identify patterns of long-term, radiation-induced swallowing dysfunction after definitive radiotherapy with or without chemotherapy (RT or CHRT) and to determine which factors may explain these patterns over time. The study population... more
    To identify patterns of long-term, radiation-induced swallowing dysfunction after definitive radiotherapy with or without chemotherapy (RT or CHRT) and to determine which factors may explain these patterns over time. The study population consisted of 238 consecutive head and neck cancer patients treated with RT or CHRT. The primary endpoint was ⩾grade 2 swallowing dysfunction at 6, 12, 18 and 24months after treatment. Cluster analysis was used to identify different patterns over time. The differences between the mean dose to the swallowing organs at risk for each pattern were determined by using dose maps. The cluster analysis revealed five patterns of swallowing dysfunction: low persistent, intermediate persistent, severe persistent, transient and progressive. Patients with high dose to the upper pharyngeal, laryngeal and lower pharyngeal region had the highest risk of severe persistent swallowing dysfunction. Transient problems mainly occurred after high dose to the laryngeal and ...
    To determine if acute symptoms during definitive radiotherapy (RT) or chemoradiation (CHRT) are prognostic factors for late dysphagia in head and neck cancer (HNC). This prospective cohort study consisted of 260 HNC patients who received... more
    To determine if acute symptoms during definitive radiotherapy (RT) or chemoradiation (CHRT) are prognostic factors for late dysphagia in head and neck cancer (HNC). This prospective cohort study consisted of 260 HNC patients who received definitive RT or CHRT. The primary endpoint was grade 2-4 swallowing dysfunction at 6months after completing RT (SWALM6). During treatment, acute symptoms, including oral mucositis, xerostomia and dysphagia, were scored, and the scores were accumulated weekly and entered into an existing reference model for SWALM6 that consisted of dose-volume variables only. Both acute xerostomia and dysphagia were strong prognostic factors for SWALM6. When acute scores were added as variables to the reference model, model performance increased as the course of treatment progressed: the AUC rose from 0.78 at the baseline to 0.85 in week 6. New models built for weeks 3-6 were significantly better able to identify patients with and without late dysphagia. Acute xeros...
    No validated predictive biomarkers for antiangiogenic treatment of metastatic renal cell carcinoma (mRCC) exist. Tumor vascular endothelial growth factor A (VEGF-A) level may be useful. We determined tumor uptake of (89)Zr-bevacizumab, a... more
    No validated predictive biomarkers for antiangiogenic treatment of metastatic renal cell carcinoma (mRCC) exist. Tumor vascular endothelial growth factor A (VEGF-A) level may be useful. We determined tumor uptake of (89)Zr-bevacizumab, a VEGF-A-binding PET tracer, in mRCC patients before and during antiangiogenic treatment in a pilot study. Patients underwent (89)Zr-bevacizumab PET scans at baseline and 2 and 6 wk after initiating either bevacizumab (10 mg/kg every 2 wk) with interferon-α (3-9 million IU 3 times/wk) (n = 11) or sunitinib (50 mg daily, 4 of every 6 wk) (n = 11). Standardized uptake values were compared with plasma VEGF-A and time to disease progression. (89)Zr-bevacizumab PET scans visualized 125 evaluable tumor lesions in 22 patients, with a median SUV(max) (maximum standardized uptake value) of 6.9 (range, 2.3-46.9). Bevacizumab/interferon-α induced a mean change in tumor SUV(max) of -47.0% (range, -84.7 to +20.0%; P < 0.0001) at 2 wk and an additional -9.7% (ra...
    To define the optimal time point for the integration of hypoxia (18)F-FAZA-PET/CT information into radiotherapy treatment planning to benefit from hypoxia modification or dose escalation treatment. Therefore, we performed a prospective... more
    To define the optimal time point for the integration of hypoxia (18)F-FAZA-PET/CT information into radiotherapy treatment planning to benefit from hypoxia modification or dose escalation treatment. Therefore, we performed a prospective cohort study, using serial hypoxic imaging ((18)F-FAZA-PET/CT) prior to and at several time-points during (chemo)radiotherapy (CHRT) in six head and neck squamous cell (HNSCC) and six non-small cell lung cancer (NSCLC) patients. The spatio-temporal dynamics of tumor hypoxia and fractional hypoxic volumes (FHV) were evaluated using a voxel-by-voxel analysis based on a (18)F-FAZA-T/B ratio of 1.4 at four time points in HNSCC patients, at baseline (FAZA-BL), at week one (FAZA-W1), two (FAZA-W2), and four (FAZA-W4) during CHRT and at three time points in NSCLC patients (baseline; W2, W4). Ten out of twelve patients showed a substantial pre-treatment tumor hypoxia representing a FHV⩾1.4 assessed by (18)F-FAZA-PET/CT. The median FHV was 38% (FAZA-BL), 15% (...
    The biogenic amines dopamine and serotonin are neurotransmitters and hormones, which are mainly produced in the central nervous system and in the gastro-intestinal tract. They execute local and systemic functions such as intestinal... more
    The biogenic amines dopamine and serotonin are neurotransmitters and hormones, which are mainly produced in the central nervous system and in the gastro-intestinal tract. They execute local and systemic functions such as intestinal motility and tissue repair. Dopamine and serotonin are primarily stored in and transported by platelets. This review focuses on the recently recognized role of dopamine and serotonin in the regulation of tumor behavior by affecting angiogenesis and tumor cell proliferation. Preclinical studies demonstrate that dopamine inhibits tumor growth via activation of dopamine receptor D2 on endothelial and tumor cells. Serotonin stimulates tumor growth via activation of serotonin receptor 2B on endothelial cells and serotonin receptors on tumor cells. Drugs that stimulate dopamine receptor D2 or inhibit serotonin receptors are available and therefore clinical intervention studies for cancer patients are within reach.
    In solid tumors, angiogenesis occurs in the setting of a defective vasculature and impaired lymphatic drainage that is associated with increased vascular permeability and enhanced tumor permeability. These universal aspects of the tumor... more
    In solid tumors, angiogenesis occurs in the setting of a defective vasculature and impaired lymphatic drainage that is associated with increased vascular permeability and enhanced tumor permeability. These universal aspects of the tumor microenvironment can have a marked influence on intratumoral drug delivery that may often be underappreciated. In this study, we investigated the effect of blood vessel normalization in tumors by the antiangiogenic drug bevacizumab on antibody uptake by tumors. In mouse xenograft models of human ovarian and esophageal cancer (SKOV-3 and OE19), we evaluated antibody uptake in tumors by positron emission tomographic imaging 24 and 144 hours after injection of (89)Zr-trastuzumab (SKOV-3 and OE19), (89)Zr-bevacizumab (SKOV-3), or (89)Zr-IgG (SKOV-3) before or after treatment with bevacizumab. Intratumor distribution was assessed by fluorescence microscopy along with mean vessel density (MVD) and vessel normalization. Notably, bevacizumab treatment decreased tumor uptake and intratumoral accumulation compared with baseline in the tumor models relative to controls. Bevacizumab treatment also reduced MVD in tumors and increased vessel pericyte coverage. These findings are clinically important, suggesting caution in designing combinatorial trials with therapeutic antibodies due to a possible reduction in tumoral accumulation that may be caused by bevacizumab cotreatment.
    Non-invasive imaging of angiogenesis could ease the optimization of antiangiogenesis treatments for cancer. In this study, we evaluated the role of VEGF-PET as a biomarker of dynamic angiogenic changes in tumors following treatment with... more
    Non-invasive imaging of angiogenesis could ease the optimization of antiangiogenesis treatments for cancer. In this study, we evaluated the role of VEGF-PET as a biomarker of dynamic angiogenic changes in tumors following treatment with the kinase inhibitor sunitinib. The effects of sunitinib treatment and withdrawal on the tumor was investigated using the new VEGF-PET tracer (89)Zr-ranibizumab as well as (18)F-FDG PET, and (15)O-water PET in mouse xenograft models of human cancer. The obtained imaging results were compared with tumor growth, VEGF plasma levels and immunohistologic analyzes. In contrast to (18)F-FDG and (15)O-water PET, VEGF-PET demonstrated dynamic changes during sunitinib treatment within the tumor with a strong decline in signal in the tumor center and only minimal reduction in tumor rim, with a pronounced rebound after sunitinib discontinuation. VEGF-PET results corresponded with tumor growth and immunohistochemical vascular- and tumor- markers. Our findings highlight the strengths of VEGF-PET imaging to allow serial analysis of angiogenic changes in different areas within a tumor.