FMISO PET Imaging Research Articles

[18F]FMISO-PET imaging reveals the role of hypoxia severity in checkpoint blockade response

ContextHypoxia within the tumor microenvironment is a critical factor influencing the efficacy of immunotherapy, including immune checkpoint inhibition. Insufficient oxygen supply, characteristic of hypoxia, has been recognized as a central determinant in the progression of various cancers. The reemergence of evofosfamide, a hypoxia-activated prodrug, as a potential treatment strategy has sparked interest in addressing the role of hypoxia in immunotherapy response. This investigation sought to understand the kinetics and heterogeneity of tumor hypoxia and their implications in affecting responses to immunotherapeutic interventions with and without evofosfamide. PurposeThis study aimed to investigate the influence of hypoxia on immune checkpoint inhibition, evofosfamide monotherapy, and their combination on colorectal cancer (CRC). Employing positron emission tomography (PET) imaging, we developed novel analytical methods to quantify and characterize tumor hypoxia severity and distribution. ProceduresMurine CRC models were longitudinally imaged with [18F]-fluoromisonidazole (FMISO)-PET to quantify tumor hypoxia during checkpoint blockade (anti-CTLA-4 + and anti-PD1 +/− evofosfamide). Metrics including maximum tumor [18F]FMISO uptake (FMISOmax) and mean tumor [18F]FMISO uptake (FMISOmean) were quantified and compared with normal muscle tissue (average muscle FMISO uptake (mAvg) and muscle standard deviation (mSD)). Histogram distributions were used to evaluate heterogeneity of tumor hypoxia. FindingsSevere hypoxia significantly impeded immunotherapy effectiveness consistent with an immunosuppressive microenvironment. Hypoxia-specific PET imaging revealed a striking degree of spatial heterogeneity in tumor hypoxia, with some regions exhibiting significantly more severe hypoxia than others. The study identified FMISOmax as a robust predictor of immunotherapy response, emphasizing the impact of localized severe hypoxia on tumor volume control during therapy. Interestingly, evofosfamide did not directly reduce hypoxia but markedly improved the response to immunotherapy, uncovering an alternative mechanism for its efficacy. ConclusionsThese results enhance our comprehension of the interplay between hypoxia and immune checkpoint inhibition within the tumor microenvironment, offering crucial insights for the development of personalized cancer treatment strategies. Non-invasive hypoxia quantification through molecular imaging evaluating hypoxia severity may be an effective tool in guiding treatment planning, predicting therapy response, and ultimately improving patient outcomes across diverse cancer types and tumor microenvironments. It sets the stage for the translation of these findings into clinical practice, facilitating the optimization of immunotherapy regimens by addressing tumor hypoxia and thereby enhancing the efficacy of cancer treatments.

Dual anti-HER2/EGFR inhibition synergistically increases therapeutic effects and alters tumor oxygenation in HNSCC

Epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and hypoxia are associated with radioresistance. The goal of this study is to study the synergy of anti-HER2, trastuzumab, and anti-EGFR, cetuximab, and characterize the tumor microenvironment components that may lead to increased radiation sensitivity with dual anti-HER2/EGFR therapy in head and neck squamous cell carcinoma (HNSCC). Positron emission tomography (PET) imaging ([89Zr]-panitumumab and [89Zr]-pertuzumab) was used to characterize EGFR and HER2 in HNSCC cell line tumors. HNSCC cells were treated with trastuzumab, cetuximab, or combination followed by radiation to assess for viability and radiosensitivity (colony forming assay, immunofluorescence, and flow cytometry). In vivo, [18F]-FMISO-PET imaging was used to quantify changes in oxygenation during treatment. Bliss Test of Synergy was used to identify combination treatment synergy. Quantifying EGFR and HER2 receptor expression revealed a 50% increase in heterogeneity of HER2 relative to EGFR. In vitro, dual trastuzumab-cetuximab therapy shows significant decreases in DNA damage response and increased response to radiation therapy (p < 0.05). In vivo, tumors treated with dual anti-HER2/EGFR demonstrated decreased tumor hypoxia, when compared to single agent therapies. Dual trastuzumab-cetuximab demonstrates synergy and can affect tumor oxygenation in HNSCC. Combination trastuzumab-cetuximab modulates the tumor microenvironment through reductions in tumor hypoxia and induces sustained treatment synergy.

Molecular Imaging of Oxygenation Changes during Immunotherapy in Combination with Paclitaxel in Triple Negative Breast Cancer.

Hypoxia is a common feature of the tumor microenvironment, including that of triple-negative breast cancer (TNBC), an aggressive breast cancer subtype with a high five-year mortality rate. Using [18F]-fluoromisonidazole (FMISO) positron emission tomography (PET) imaging, we aimed to monitor changes in response to immunotherapy (IMT) with chemotherapy in TNBC. TNBC-tumor-bearing mice received paclitaxel (PTX) ± immune checkpoint inhibitors anti-programmed death 1 and anti-cytotoxic T-lymphocyte 4. FMISO-PET imaging was performed on treatment days 0, 6, and 12. Max and mean standard uptake values (SUVmax and SUVmean, respectively), histological analyses, and flow cytometry results were compared. FMISO-PET imaging revealed differences in tumor biology between treatment groups prior to tumor volume changes. 4T1 responders showed SUVmean 1.6-fold lower (p = 0.02) and 1.8-fold lower (p = 0.02) than non-responders on days 6 and 12, respectively. E0771 responders showed SUVmean 3.6-fold lower (p = 0.001) and 2.7-fold lower (p = 0.03) than non-responders on days 6 and 12, respectively. Immunohistochemical analyses revealed IMT plus PTX decreased hypoxia and proliferation and increased vascularity compared to control. Combination IMT/PTX recovered the loss of CD4+ T-cells observed with single-agent therapies. PET imaging can provide timely, longitudinal data on the TNBC tumor microenvironment, specifically intratumoral hypoxia, predicting therapeutic response to IMT plus chemotherapy.

OC-0627 TCP predictions of an automated dose painting strategy based on FDG and FMISO PET imaging

OC-0627 TCP predictions of an automated dose painting strategy based on FDG and FMISO PET imaging

Interleukin-6 as surrogate marker for imaging-based hypoxia dynamics in patients with head-and-neck cancers undergoing definitive chemoradiation—results from a prospective pilot trial

PurposeIntratumoral hypoxia increases resistance of head-and-neck squamous cell carcinoma (HNSCC) to radiotherapy. [18F]FMISO PET imaging enables noninvasive hypoxia monitoring, though requiring complex logistical efforts. We investigated the role of plasma interleukin-6 (IL-6) as potential surrogate parameter for intratumoral hypoxia in HNSCC using [18F]FMISO PET/CT as reference.MethodsWithin a prospective trial, serial blood samples of 27 HNSCC patients undergoing definitive chemoradiation were collected to analyze plasma IL-6 levels. Intratumoral hypoxia was assessed in treatment weeks 0, 2, and 5 using [18F]FMISO PET/CT imaging. The association between PET-based hypoxia and IL-6 was examined using Pearson’s correlation and multiple regression analyses, and the diagnostic power of IL-6 for tumor hypoxia response prediction was determined with receiver-operating characteristic analyses.ResultsMean IL-6 concentrations were 15.1, 19.6, and 31.0 pg/mL at baseline, week 2 and week 5, respectively. Smoking (p=0.050) and reduced performance status (p=0.011) resulted in higher IL-6 levels, whereas tumor (p=0.427) and nodal stages (p=0.334), tumor localization (p=0.439), and HPV status (p=0.294) had no influence. IL-6 levels strongly correlated with the intratumoral hypoxic subvolume during treatment (baseline: r=0.775, p<0.001; week 2: r=0.553, p=0.007; week 5: r=0.734, p<0.001). IL-6 levels in week 2 were higher in patients with absent early tumor hypoxia response (p=0.016) and predicted early hypoxia response (AUC=0.822, p=0.031). Increased IL-6 levels at week 5 resulted in a trend towards reduced progression-free survival (p=0.078) and overall survival (p=0.013).ConclusionPlasma IL-6 is a promising surrogate marker for tumor hypoxia dynamics in HNSCC patients and may facilitate hypoxia-directed personalized radiotherapy concepts.Trial registrationThe prospective trial was registered in the German Clinical Trial Register (DRKS00003830). Registered 20 August 2015

Abstract 3058: Molecular imaging of hypoxia to evaluate synergy between HER2 targeted therapy and fractionated radiation in murine models of HER2+ breast cancer

Abstract Introduction: Tumor hypoxia contributes to intra-tumoral heterogeneity and decreases efficacy of cytotoxic therapy. Fractionated radiation is a component of standard-of-care therapy for patients with unresectable human epidermal growth factor receptor 2 (HER2+) breast cancer. This study investigates if [18F]-fluoromisonidazole (FMISO)-PET imaging can quantify anti-HER2 therapy-induced changes in tumor oxygenation and utilize imaging metrics to monitor the synergy of combination targeted and fractionated radiation. Improving treatment synergy in HER2+ breast cancer has potential to increase therapeutic efficacy without increasing cytotoxic therapy. Methods: For in vivo studies, HER2+ cell line (BT474 and MDA-MB-361) and HER2+ patient derived xenograft (BCM 3472) tumor models were engrafted in mice and treated with single agent or combination trastuzumab (4 mg/kg) and fractionated radiation (6/3 Gy). Mice were imaged with FMISO-PET imaging on days 0, 3, and 7 to monitor changes in tumor hypoxia. Hypoxic fraction within the tumor was quantified by a voxel-wise basis with a hypoxic threshold of mean standardized uptake value (SUV) of the muscle + 1 STD. Tumors were either extracted for biological validation of imaging or continued to measure tumor size changes for longitudinal assessment of response. Immunohistochemical analysis included staining for pimonidazole (hypoxia), CD-31 (microvessel), cleaved caspase-3 (apoptosis) and Ki-67 (proliferation). Bliss test of independence and a non-parametric T-test was used to assess for treatment synergy and significance, respectively. Results: In vivo, MDA-MB-361 tumors treated with trastuzumab and fractionated radiation revealed a SUVmean of 0.20 ± 0.09 on day 7, while tumors treated with fractionated radiation had a FMISO SUVmean of 0.31 ± 0.06 (p=0.05). MDA-MB-361 tumors treated with a control or fractionated radiation were 93.7% and 87.7% hypoxic, respectively; whereas, tumors treated with trastuzumab + fractionated radiation were significantly decreased (76.3% hypoxic, p=0.05 and p=0.26, respectively). 30 days after start of therapy, BCM3472 tumors treated with single agent fractionated radiation had a tumor volume of 285.3 ± 59 mm3, whereas tumors treated with trastuzumab and fractionated radiation had a tumor volume of 104 ± 24 mm3 (p&amp;lt;0.05). Treatment synergy started 14 days after start of therapy. Conclusion: HER2+ breast cancer treated with trastuzumab prior to fractionated radiation decreases hypoxia and synergistically increases efficacy of radiotherapy. FMISO-PET imaging has potential to identify in vivo response to combination therapies and better understand changes in the tumor microenvironment to guide combination therapy. Citation Format: Patrick Song, Yun Lu, Sharon Samuel, Katherine Heinzman, Suzanne Lapi, Anna Sorace. Molecular imaging of hypoxia to evaluate synergy between HER2 targeted therapy and fractionated radiation in murine models of HER2+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3058.

Abstract PS10-21: Identifying efficacy of targeted HER2 antibodies in sensitization of HER2 positive breast cancer to fractionated radiation

Abstract Introduction: Tumor hypoxia contributes to intra-tumoral heterogeneity and decreases efficacy of cytotoxic therapy. Fractionated radiation therapy has emerged as an alternative to single dose radiation, and is a component of standard-of-care therapy for patients with unresectable human epidermal growth factor receptor 2 (HER2+) breast cancer. Because radiation therapy is dependent on tissue oxygenation, therapies that increase oxygenation could radio-sensitize tumors. The goal of this study is to investigate if molecular imaging with [18F]-fluoromisonidazole (FMISO)-PET can quantify anti-HER2 therapy-induced changes in tumor oxygenation and utilize imaging metrics to enhance the effectiveness of fractionated radiation. Improving treatment synergy in HER2+ breast cancer has potential to increase therapeutic effectiveness without increasing cytotoxic therapy. Methods: For in vitro studies, HER2+ breast cancer cells (BT474, SKBR3, MDA-MB-361 and MDA-MB-453) were treated with various sequencing of combination trastuzumab (1 µg/mL) and fractionated radiation (6/3 Gy) and assessed for cell death. HER2+ cancer cells (BT474 and MDA-MB-361) were also treated with combination trastuzumab and fractionated radiation and analyzed for DNA double strand breaks (DSB) through flow cytometry. For in vivo studies, HER2+ cell line (BT474 and MDA-MB-361) and HER2+ patient derived xenograft (BCM 3472) tumors were engrafted into mice and treated with trastuzumab (4 mg/kg) on days 0 and 3 and fractionated radiation (6/3 Gy) on days 1, 2 and 3 (or single agent control). [18F]-FMISO-PET imaging was conducted on day 0, 3 and 7. At the imaging endpoint, tumors were either extracted for biological validation or continued to measure tumor size changes for longitudinal assessment of response. Bliss test of independence and a non-parametric T-test was used to assess for treatment synergy and significance, respectively. Results: In vitro cell death assay revealed single agent trastuzumab or fractionated radiation treated groups exhibited 15.2% ± 6.5% or 53.6% ± 9% cell death respectively, while trastuzumab prior to fractionated radiation groups exhibited 72.5% ± 2.5% cell death (p = 0.01) on day 7 in MDA-MB-361 cells. Flow cytometry analysis showed MDA-MB-361 cells treated with trastuzumab prior to fractionated radiation exhibited 62.4% ± 8.7% DSB, which significantly increased from single agent trastuzumab (0.74% ± 0.39%) or fractionated radiation groups (37.3% ± 7.3%) (p = 0.01). In vivo, MDA-MB-361 tumors treated with trastuzumab and fractionated radiation had a [18F]-FMISO SUVmean of 0.20 ± 0.09, while tumors treated with fractionated radiation had a [18F]-FMISO SUVmean of 0.31 ± 0.06 on day 7 (p = 0.05). MDA-MB-361 tumors treated with trastuzumab and fractionated radiation experienced a 26.1% ± 16.8% decrease in tumor volume, while tumors treated with single agent fractionated radiation experienced a 10.4% ± 2.8% decrease in tumor volume from day 0 to day 7 (p = 0.11). 30 days after start of therapy, MDA-MB-361 tumors treated with single agent fractionated radiation had a tumor volume of 471.8 ± 120 mm3, whereas tumors treated with combination trastuzumab and fractionated radiation had a tumor volume of 116 ± 38 mm3 (p &amp;lt; 0.01). Bliss test of independence confirmed in vivo treatment synergy of trastuzumab and fractionated radiation starting 14 days after start of therapy. Conclusion: HER2+ breast cancer treated with trastuzumab prior to fractionated radiation synergistically increases efficacy of radiotherapy in vitro and in vivo. [18F]-FMISO-PET imaging has potential to identify in vivo response to combination therapies and better understand changes in the tumor microenvironment to guide combination therapy. Acknowledgements: We thank the American Cancer Society for RSG-18-006-01-CCE and NIH NCI R01 CA240589. Citation Format: Patrick N. Song, Yun Lu, Tiara Napier, Sharon Samuel, Katherine Heinzman, Suzanne E. Lapi, Anna G. Sorace. Identifying efficacy of targeted HER2 antibodies in sensitization of HER2 positive breast cancer to fractionated radiation [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS10-21.

18F]FMISO PET/CT imaging of hypoxia as a non-invasive biomarker of disease progression and therapy efficacy in a preclinical model of pulmonary fibrosis: comparison with the [18F]FDG PET/CT approach

PurposeIdiopathic pulmonary fibrosis (IPF) is a progressive disease with poor outcome and limited therapeutic options. Imaging of IPF is limited to high-resolution computed tomography (HRCT) which is often not sufficient for a definite diagnosis and has a limited impact on therapeutic decision and patient management. Hypoxia of the lung is a significant feature of IPF but its role on disease progression remains elusive. Thus, the aim of our study was to evaluate hypoxia imaging with [18F]FMISO as a predictive biomarker of disease progression and therapy efficacy in preclinical models of lung fibrosis in comparison with [18F]FDG.MethodsEight-week-old C57/BL6 mice received an intratracheal administration of bleomycin (BLM) at day (D) 0 to initiate lung fibrosis. Mice received pirfenidone (300 mg/kg) or nintedanib (60 mg/kg) by daily gavage from D9 to D23. Mice underwent successive PET/CT imaging at several stages of the disease (baseline, D8/D9, D15/D16, D22/D23) with [18F]FDG and [18F]FMISO. Histological determination of the lung expression of HIF-1α and GLUT-1 was performed at D23.ResultsWe demonstrate that mean lung density on CT as well as [18F]FDG and [18F]FMISO uptakes are upregulated in established lung fibrosis (1.4-, 2.6- and 3.2-fold increase respectively). At early stages, lung areas with [18F]FMISO uptake are still appearing normal on CT scans and correspond to areas which will deteriorate towards fibrotic lesions at later timepoints. Nintedanib and pirfenidone dramatically and rapidly decreased mean lung density on CT as well as [18F]FDG and [18F]FMISO lung uptakes (pirfenidone: 1.2-, 2.9- and 2.6-fold decrease; nintedanib: 1.2-, 2.3- and 2.5-fold decrease respectively). Early [18F]FMISO lung uptake was correlated with aggressive disease progression and better nintedanib efficacy.Conclusion[18F]FMISO PET imaging is a promising tool to early detect and monitor lung fibrosis progression and therapy efficacy.

Increased [18F]FMISO accumulation under hypoxia by multidrug-resistant protein 1 inhibitors

Background[18F]Fluoromisonidazole ([18F]FMISO) is a PET imaging probe widely used for the detection of hypoxia. We previously reported that [18F]FMISO is metabolized to the glutathione conjugate of the reduced form in hypoxic cells. In addition, we found that the [18F]FMISO uptake level varied depending on the cellular glutathione conjugation and excretion ability such as enzyme activity of glutathione-S-transferase and expression levels of multidrug resistance-associated protein 1 (MRP1, an efflux transporter), in addition to the cellular hypoxic state. In this study, we evaluated whether MRP1 activity affected [18F]FMISO PET imaging.MethodsFaDu human pharyngeal squamous cell carcinoma cells were pretreated with MRP1 inhibitors (cyclosporine A, lapatinib, or MK-571) for 1 h, incubated with [18F]FMISO for 4 h under hypoxia, and their radioactivity was then measured. FaDu tumor-bearing mice were intravenously injected with [18F]FMISO, and PET/CT images were acquired at 4 h post-injection (1st PET scan). Two days later, the same mice were pretreated with MRP1 inhibitors (cyclosporine A, lapatinib, or MK-571) for 1 h, and PET/CT images were acquired (2nd PET scan).ResultsFaDu cells pretreated with MRP1 inhibitors exhibited significantly higher radioactivity than those without inhibitor treatment (cyclosporine A: 6.91 ± 0.27, lapatinib: 10.03 ± 0.47, MK-571: 10.15 ± 0.44%dose/mg protein, p < 0.01). In the in vivo PET study, the SUVmean ratio in tumors [calculated as after treatment (2nd PET scan)/before treatment of MRP1 inhibitors (1st PET scan)] of the mice treated with MRP1 inhibitors was significantly higher than those of control mice (cyclosporine A: 2.6 ± 0.7, lapatinib: 2.2 ± 0.7, MK-571: 2.2 ± 0.7, control: 1.2 ± 0.2, p < 0.05).ConclusionIn this study, we revealed that MRP1 inhibitors increase [18F]FMISO accumulation in hypoxic cells. This suggests that [18F]FMISO-PET imaging is affected by MRP1 inhibitors independent of the hypoxic state.

18F-FMISO PET imaging: insights over MRI in patients with glioma

Hypoxic tumors have been demonstrated to be associated with amplified resistance to radiotherapy, chemo-resistance and less favorable outcome after surgery. Non-invasive identification and quantification of hypoxia in humans affected by glioma can be achieved using PET/CT and MRI techniques, although their use is still limited to the research setting. The objective of this review is to present an update of the literature about the potential clinical utility of FMISO PET imaging for the evaluation of hypoxia in patients with glioma, in comparison with advanced MRI techniques, when available. A comprehensive search strategy was used based on SCOPUS and PubMed databases using the following terms: “FMISO”/“Fluoromisonidazole” AND “brain tumor”/“glioma” AND “PET”/“Positron Emission Tomography”. From all studies published in English, we selected—for this review—the most relevant articles of the last 20 years, evaluating the use of FMISO PET in glioma patients, and comparing PET findings with MRI imaging (when available). The use of PET/CT with hypoxia radiotracers in glioma is still limited due to fragmentary data and scarce number of clinical trials in this setting. The most used PET radiotracer for the quantification of hypoxia brain tumor is 18F-FMISO and advanced MRI techniques may provide additional value, especially to couple perfusion information to hypoxia data obtained by PET. As example, relative cerebral blood volume maps could be integrated with PET imaging results for more precise and integrated evaluation of hypoxia, neo-angiogenesis and necrotic areas. Hypoxia PET imaging has demonstrated potential benefits for grading, diagnostic and prognostic purposes, despite the lack of tangible results able to introduce such method in a wide clinical setting. MRI remains the gold standard in the morphologic evaluation of glioma, but the integration of results provided by 18F-FMISO PET imaging concerning hypoxia might provide new crucial information in patients with glioma.

Correlative Analyses between Tissue-Based Hypoxia Biomarkers and Hypoxia PET Imaging in Head and Neck Cancer Patients during Radiochemotherapy: Results from a Prospective Trial

Tumor hypoxia influences the response of head and neck cancer (HNSCC) patients to radiotherapy and is associated with reduced outcomes. While both tissue-based hypoxia biomarkers and hypoxia PET imaging have previously been correlated with patient outcomes, the goal of this analysis was to evaluate potential correlations between biological markers and longitudinal biological imaging in a prospective trial of HNSCC patients. Forty-nine patients with locally advanced HNSCCs scheduled for definitive chemoradiation were enrolled in this prospective trial. They underwent baseline biopsies and [18F]FMISO PET imaging at baseline and at weeks 2 and 5 during treatment as well as [18F]FDG PET imaging at baseline. Immunohistochemical analyses for p16, Ki67, CD34-dependent microvascular density, hypoxia-inducible factor 1 α (HIF1α), carbonic anhydrase 9 (CAIX), Ku80 and CD44 were performed, and HPV status was assessed from tumor biopsies. Biomarker expression was quantified by the H-score and correlated with biological imaging information (Pearson product-moment correlation coefficient) and patient outcome data (Cox regression analysis). High HIF1α H-scores in the tumor were found to significantly correlate with increased tumor hypoxia during the first weeks of treatment as assessed by the difference in the FMISO tumor-to-background ratios (TBR) between baseline and week 2 (r=0.35; p<0.05) and deferred decrease in FMISO uptake between weeks 2 and 5 (r=0.35; p<0.05). Similarly, high CAIX H-scores were associated with a delayed reduction in FMISO TBR between weeks 2 and 5 (r=-0.39; p<0.05). Clinically, patients with high expression of CAIX exhibited significantly increased loco-regional recurrence rates after chemoradiation (hazard ratio 2.80 [1.08 – 7.31]; p<0.05). Additionally, loco-regional recurrence was associated with high expression of the DNA repair factor Ku80 in the tumor, although statistical significance was not reached. HPV status did not correlate with any of the tested biomarkers, and HPV-positive patients showed lower loco-regional recurrence rates (hazard ratio 0.13 [0.02 – 0.99]; p<0.01) and overall survival (hazard ratio 0.03 [0.001 – 1.73]; p<0.01) independent of their hypoxia dynamics and expression of tissue-based hypoxia biomarkers. In this trial, high expression of the tissue-based hypoxia biomarkers HIF1α and CAIX at baseline correlated with adverse hypoxia dynamics in HNSCCs during chemoradiation as assessed by PET imaging, and high CAIX levels were associated with increased loco-regional recurrence rates. Hence, tissue-based hypoxia biomarkers may be useful as predictors of hypoxia-associated radiation resistance and response of HNSCCs and warrant further investigations.

EP-1915 Modelling framework for FMISO and FDG PET imaging tailored dose prescription

EP-1915 Modelling framework for FMISO and FDG PET imaging tailored dose prescription

Repeat FMISO-PET imaging weakly correlates with hypoxia-associated gene expressions for locally advanced HNSCC treated by primary radiochemotherapy

BackgroundHypoxia is an important factor of tumour resistance to radiotherapy, chemotherapy and potentially immunotherapy. It can be measured e.g. by positron emission tomography (PET) imaging or hypoxia-associated gene expressions from tumour biopsies. Here we correlate [18F]fluoromisonidazole (FMISO)-PET/CT imaging with hypoxia-associated gene expressions on a cohort of 50 head and neck squamous cell carcinoma (HNSCC) patients and compare their prognostic value for response to radiochemotherapy (RCTx). MethodsFMISO-PET/CT images of 50 HNSCC patients were acquired at four time-points before and during RCTx. For 42 of these patients, hypoxia-associated gene expressions were evaluated by nanoString technology based on a biopsy obtained before any treatment. The FMISO-PET parameters tumour-to-background ratio and hypoxic volume were correlated to the expressions of 58 hypoxia-associated genes using the Spearman correlation coefficient ρ. Three hypoxia-associated gene signatures were compared regarding their correlation with the FMISO-PET parameters using their median expression. In addition, the correlation with tumour volume was analysed. The impact of both hypoxia measurement methods on loco-regional tumour control (LRC) and overall survival (OS) was assessed by Cox regression. ResultsThe median expression of hypoxia-associated genes was weakly correlated to hypoxia measured by FMISO-PET imaging (ρ ≤ 0.43), with higher correlations to imaging after weeks 1 and 2 of treatment (p < 0.001). Moderate correlations were obtained between FMISO-PET imaging and tumour volume (ρ ≤ 0.69). Prognostic models for LRC and OS based on the FMISO-PET parameters could not be improved by including hypoxia classifiers. ConclusionWe observed low correlations between hypoxia FMISO-PET parameters and expressions of hypoxia-associated genes. Since FMISO-PET showed a superior patient stratification, it may be the preferred biomarker over hypoxia-associated genes for stratifying patients with locally advanced HNSCC treated by primary RCTx.

Geometric analysis of loco-regional recurrences in relation to pre-treatment hypoxia in patients with head and neck cancer

Introduction: A previous pattern-of-failure study has suggested that up to 50% of the loco-regional failures (LRF) in head and neck squamous cell carcinoma (HNSCC) occur outside the initial hypoxic volume determined by [18F]-fluoromisonidazole-PET ([18F]-FMISO-PET). The aim of the present analysis was to correlate spatial patterns of failure with respect to the pretherapeutic dynamic [18F]-FMISO-PET/CT in HNSCC after radiochemotherapy (RCT).Material and methods: Within a running phase 2 trial using [18F]-FMISO-PET imaging prior to RCT in HNSCC patients (n = 54), we have observed so far 11 LRF with a minimum follow-up of 12 months. For nine patients, LRF imaging (CT or [18F]-FDG-PET/CT) for pattern-of-failure analysis was available. Analysis included the static 4-h hypoxic subvolume (VH) as well as a M-parameter volume (VM), which is derived from modeling of dynamic PET. Deformable image registration of the CT scan with the recurrent tumor to the pre-treatment [18F]-FMISO-PET/CT and the planning CT was done to quantify the hypoxic subvolumes compared to the recurrent tumor volume. Moreover, a point-of-origin analysis was performed.Results: A total of five local, two regional and two loco-regional recurrences were detected. After deformable image registration of the CT scan with the recurrent tumor to the pre-treatment [18F]-FMISO-PET/CT and the planning CT, a significant overlap of the recurrence volume with [18F]-FMISO-positive subvolumes in the initial gross tumor volume (GTV) was observed. Median overlap of 40.2%, range 9.4–100.0%, for VH and 49.0%, range 4.4–96.4%, for VM was calculated. The point-of-origin analysis showed median distances of 0.0 mm, range 0.0–11.3 mm to VH and 8.6 mm, range 0.0–15.5 mm to VM, respectively.Conclusions: Our data suggest that loco-regional recurrences after RCT originate from the initial GTV (primary tumor and/or lymph node metastases) containing hypoxic subvolumes, which supports the concept of hypoxia imaging-based dose escalation.

Abstract B029: OMX: An oxygen carrier biotherapeutic that ameliorates the hypoxic tumor microenvironment and promotes anticancer T cell activity

Abstract A hypoxic microenvironment is a hallmark of cancer that has been shown in numerous cancer types to drive tumor progression and poor patient outcomes. Hypoxia promotes tumor evasion of the host immune responses by generating an immunosuppressive tumor microenvironment through activation of multiple pathways mediated predominantly, but not exclusively, by hypoxia inducible factor-1 (HIF-1) signaling. We have previously shown that Omniox' lead anti-cancer immunotherapeutic, OMX, is well tolerated in small and large animals, efficiently accumulates in a variety of orthotopic and subcutaneous rodent tumor models and spontaneous canine melanomas and brain cancers, and effectively reduces tumor hypoxia as assessed by ex vivo immunoassays using hypoxia markers, in vivo FMISO PET imaging, and direct intratumor pO2 measurements with optical probes. Here, we used a combination of quantitative immunohistochemistry and flow cytometry to analyze the effects of OMX treatment and dosing regiment on leukocyte infiltration and activity in normoxic and hypoxic tumor regions in multiple syngeneic mouse tumor models (MC38, CT26, 4T1, B16F10). First, we confirmed in our models published findings that cytotoxic T cells (CTL) are predominantly excluded from hypoxic tumor areas. Next, we explored the effect of single and multi-dose OMX treatments on tumor immune cell populations, and demonstrated that a single iv administration of OMX reduces hypoxia and enhances T cell localization in previously hypoxic tumor areas labelled by two independent markers of hypoxia (pimonidazole and CAIX). Furthermore, 12h after a single OMX treatment we observed &amp;gt;85% intra-tumor reduction in immunosuppressive regulatory T cells (Treg). Tumor Treg reduction was maintained and even more pronounced with repeated dosing, resulting in long-term Treg depletion. Importantly, OMX treatment resulted in a 5-10 fold higher CTL/Treg ratio concomitant with a 3-fold increase in the fraction of activated effector T lymphocytes, with no effect on overall leukocyte populations within the tumor. Taken together, our data suggest that OMX treatment changes the tumor microenvironment from an immunosuppressive to an immunopermissive state in multiple tumor types. Results from ongoing OMX+checkpoint inhibitor combination studies will also be presented. In conclusion, by delivering oxygen specifically to the hypoxic tumor microenvironment, OMX may restore anti-cancer immune responses in cancer patients. Given that OMX is well-tolerated and that its mechanism of action is upstream of major immunosuppressive pathways, OMX holds the potential to synergize with multiple immunotherapeutic agents in enhancing tumor control and improving patient outcomes in solid tumors. Citation Format: Kevin G. Leong, Natacha Le Moan, Yuqiong Pan, Philberta Leung, Catherine Bedard, Jon Winger, Stephen PL Cary, Ana Krtolica. OMX: An oxygen carrier biotherapeutic that ameliorates the hypoxic tumor microenvironment and promotes anticancer T cell activity [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B029.

Pathophysiologic Mechanisms of Cerebral Ischemia and Diffusion Hypoxia in Traumatic Brain Injury.

Combined oxygen 15-labeled positron emission tomography (15O PET) and brain tissue oximetry have demonstrated increased oxygen diffusion gradients in hypoxic regions after traumatic brain injury (TBI). These data are consistent with microvascular ischemia and are supported by pathologic studies showing widespread microvascular collapse, perivascular edema, and microthrombosis associated with selective neuronal loss. Fluorine 18-labeled fluoromisonidazole ([18F]FMISO), a PET tracer that undergoes irreversible selective bioreduction within hypoxic cells, could confirm these findings. To combine [18F]FMISO and 15O PET to demonstrate the relative burden, distribution, and physiologic signatures of conventional macrovascular and microvascular ischemia in early TBI. This case-control study included 10 patients who underwent [18F]FMISO and 15O PET within 1 to 8 days of severe or moderate TBI. Two cohorts of 10 healthy volunteers underwent [18F]FMISO or 15O PET. The study was performed at the Wolfson Brain Imaging Centre of Addenbrooke's Hospital. Cerebral blood flow, cerebral blood volume, cerebral oxygen metabolism (CMRO2), oxygen extraction fraction, and brain tissue oximetry were measured in patients during [18F]FMISO and 15O PET imaging. Similar data were obtained from control cohorts. Data were collected from November 23, 2007, to May 22, 2012, and analyzed from December 3, 2012, to January 6, 2016. Estimated ischemic brain volume (IBV) and hypoxic brain volume (HBV) and a comparison of their spatial distribution and physiologic signatures. The 10 patients with TBI (9 men and 1 woman) had a median age of 59 (range, 30-68) years; the 2 control cohorts (8 men and 2 women each) had median ages of 53 (range, 41-76) and 45 (range, 29-59) years. Compared with controls, patients with TBI had a higher median IBV (56 [range, 9-281] vs 1 [range, 0-11] mL; P < .001) and a higher median HBV (29 [range, 0-106] vs 9 [range, 1-24] mL; P = .02). Although both pathophysiologic tissue classes were present within injured and normal appearing brains, their spatial distributions were poorly matched. When compared with tissue within the IBV compartment, the HBV compartment showed similar median cerebral blood flow (17 [range, 11-40] vs 14 [range, 6-22] mL/100 mL/min), cerebral blood volume (2.4 [range, 1.6- 4.2] vs 3.9 [range, 3.4-4.8] mL/100 mL), and CMRO2 (44 [range, 27-67] vs 71 [range, 34-88] μmol/100 mL/min) but a lower oxygen extraction fraction (38% [range, 29%-50%] vs 89% [range, 75%-100%]; P < .001), and more frequently showed CMRO2 values consistent with irreversible injury. Comparison with brain tissue oximetry monitoring suggested that the threshold for increased [18F]FMISO trapping is probably 15 mm Hg or lower. Tissue hypoxia after TBI is not confined to regions with structural abnormality and can occur in the absence of conventional macrovascular ischemia. This physiologic signature is consistent with microvascular ischemia and is a target for novel neuroprotective strategies.

On the Reliability of Automatic Volume Delineation in Low-Contrast [(18)F]FMISO-PET Imaging.

Hypoxia is a marker of poor prognosis in malignant tumors independent from the selected therapeutic method and the therapy should be intensified in such tumors. Hypoxia imaging with positron emission tomography (PET) is limited by low contrast to noise ratios with every available tracer. In radiation oncology appropriate delineation is required to allow therapy and intensification. While manual segmentation results are highly dependent from experience and observers condition (high inter- and intra observer variability), threshold- and gradient-based algorithms for automatic segmentation frequently fail in low contrast data sets. Likewise, calibration of these algorithms using phantoms is not useful. Complex computational models such as swarm intelligence-based algorithms are promising tools for optimized segmentation results and allow observer independent interpretation of multimodal and multidimensional imaging data.

Potential of [18F]-Fluoromisonidazole positron-emission tomography for radiotherapy planning in head and neck squamous cell carcinomas

Positron-emission tomography (PET) with [(18)F]-fluoromisonidazole (FMISO) permits consideration of radiotherapy dose escalation to hypoxic volumes in head and neck cancers (HNC). However, the definition of FMISO volumes remains problematic. The aims of this study are to confirm that delayed acquisition at 4 h is most appropriate for FMISO-PET imaging and to assess different methods of volume segmentation. A total of 15 HNC patients underwent several FMISO-PET/computed tomography (CT) acquisitions 2, 3 and 4 h after FMISO injection. Three automatic methods of PET image segmentation were tested: fixed threshold, adaptive threshold based on the ratio between tumour-derived and background activities (R(T/B)) and the fuzzy locally adaptive Bayesian (FLAB) method. The hypoxic fraction (HF), which is defined as the ratio between the FMISO and CT volumes, was also calculated. The R(T/B) for images acquired at 2, 3 and 4 h differed significantly, with mean values of 2.5 (1.7-2.9), 3 (2-4.5) and 3.4 (2.3-6.1), respectively. The mean tumour volume, as defined manually using CT images, was 39.1 ml (1.2-116 ml). After 4 h, the mean FMISO volumes were 18.9 (0.1-81), 9.5 (0.9-33.1) and 12.5 ml (0.9-38.4 ml) with fixed threshold, adaptive threshold and the FLAB method, respectively; median HF values were 0.47 (0.1-1.93), 0.25 (0.11-0.75) and 0.35 (0.14-1.05), respectively. FMISO volumes were significantly different. The best contrast is obtained at the 4-hour acquisition time. Large discrepancies were found between the three tested methods of volume segmentation.

ACRIN 6684 assessment of tumor hypoxia in glioblastoma using 18F-fluoromisonidazole with PET and MRI.

TPS10635 Background: Glioblastoma (GBM) is an aggressive type of primary malignant brain tumor and despite treatment with surgery, radiation, and temozolomide (TMZ) chemotherapy, median overall survival (OS) remains poor. A pathologic hallmark of GBM is tumor necrosis, a suspected result from endogenous tumor hypoxia. Angiogenesis is stimulated by hypoxia-driven signaling cascades and is required for tumor proliferation. The inefficient blood supply of these hypoxic tumors also limits the efficacy of chemotherapy and radiotherapy. Surviving hypoxic tumor cells may be selected out and proliferate as a more aggressive tumor subtype, therefore hindering OS. 18F-Fluoromisonidazole (FMISO) is a PET radiotracer whose uptake in hypoxic tissues can be measured radiographically. The degree of tumor hypoxia has been negatively associated with time to tumor progression and survival (Spence et al, 2008). Knowledge of the degree/distribution of tumor hypoxia by PET uptake and perfusion MRI parameters may provide prognostic information and help guide therapy for patients with GBM. Methods: In this phase II prospective single arm multi-institution study, patients will undergo baseline FMISO PET and MR imaging two weeks prior to chemoradiotherapy (CRT). A subset of patients will receive a second FMISO PET one week prior to CRT to assess reproducibility. Clinical outcomes of OS and 6-month progression-free survival (PFS-6) will be correlated to PET and MRI parameters. Eligibility: Pathologically confirmed GBM with residual tumor after surgery (including T2/FLAIR hyperintensity consistent with tumor) scheduled to receive standard fractionated radiation therapy and temozolomide alone or with an anti-VEGF agent or PARP inhibitor. Current enrollment: 22 patients of 50 sample size Contact information: Please contact the PI, Elizabeth R. Gerstner, MD ( egerstner@partners.org ) for additional information. Significance: With a better understanding of the extent of tumor hypoxia and changes in hypoxia levels from treatment, more effective therapies could be developed to inhibit GBM growth, target hypoxic areas and individualize patient care.

Hypoxia imaging with [F-18] FMISO-PET in head and neck cancer: Potential for guiding intensity modulated radiation therapy in overcoming hypoxia-induced treatment resistance

Background and purposePositron emission tomography (PET) imaging with [F-18] fluoromisonidazole (FMISO) has been validated as a hypoxic tracer [1,2]. Head and neck cancer exhibits hypoxia, inducing aggressive biologic traits that impart resistance to treatment. Delivery of modestly higher radiation doses to tumors with stable areas of chronic hypoxia can improve tumor control [3]. Advanced radiation treatment planning (RTP) and delivery techniques such as intensity modulated radiation therapy (IMRT) can deliver higher doses to a small volume without increasing morbidity. We investigated the utility of co-registered FMISO-PET and CT images to develop clinically feasible RTPs with higher tumor control probabilities (TCP). Materials and methodsFMISO-PET images were used to determine hypoxic sub-volumes for boost planning. Example plans were generated for 10 of the patients in the study who exhibited significant hypoxia. We created an IMRT plan for each patient with a simultaneous integrated boost (SIB) to the hypoxic sub-volumes. We also varied the boost for two patients. ResultA significant (mean 17%, median 15%) improvement in TCP is predicted when the modest additional boost dose to the hypoxic sub-volume is included. ConclusionCombined FMISO-PET imaging and IMRT planning permit delivery of higher doses to hypoxic regions, increasing the predicted TCP (mean 17%) without increasing expected complications.