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Differential diagnosis and therapy of heterogeneous breast tumors poses a major clinical challenge. To address the need for a comprehensive, noninvasive strategy to define the molecular and functional profiles of tumors in vivo, we investigated a novel combination of metabolic PET and diffusion-weighted (DW)-MRI in the polyoma virus middle T antigen transgenic mouse model of breast cancer. The implementation of a voxelwise analysis for the clustering of intra- and intertumoral heterogeneity in this model resulted in a multiparametric profile based on [18F]Fluorodeoxyglucose ([18F]FDG)-PET and DW-MRI, which identified three distinct tumor phenotypes in vivo, including solid acinar, and solid nodular malignancies as well as cystic hyperplasia. To evaluate the feasibility of this approach for clinical use, we examined estrogen receptor-positive and progesterone receptor-positive breast tumors from five patient cases using DW-MRI and [18F]FDG-PET in a simultaneous PET/MRI system. The postsurgical in vivo PET/MRI data were correlated to whole-slide histology using the latter traditional diagnostic standard to define phenotype. By this approach, we showed how molecular, structural (microscopic, anatomic), and functional information could be simultaneously obtained noninvasively to identify precancerous and malignant subtypes within heterogeneous tumors. Combined with an automatized analysis, our results suggest that multiparametric molecular and functional imaging may be capable of providing comprehensive tumor profiling for noninvasive cancer diagnostics. Cancer Res; 76(18); 5512–22. ©2016 AACR.

Detailed description of mean and max value analysis of ADC and [18F]FDG data of tumors of tg(PyV-mT) mice.

Mean (blue) and maximal (red) ADC and [18F]FDG uptake values of the same representative 8 tumors: VOIs were drawn on the basis of the T2-weighted TSE MRI data, and transferred to the appropriate PET and ADC data. The mean and max values were determined. The comparison between mean or maximal values between the tumors revealed different trends.

Supplemental Table I is a list of abbreviations, Supplemental Table II contains the classification parameters for the different phenotypes in the mouse model and Supplemental Table III contains a summary of clinical data correlating image-derived and histology-derived tumor volumes.

More detailed description of ex-vivo procedures of mouse tumor samples

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It is well established that senescence of cancer cells can be induced by treatment with classical cytotoxic therapies but also by molecularly targeted therapies or immunotherapies, a phenomenon referred to as therapy induced senescence (TIS). Occurrence of intratumoral senescence harbors broad therapeutic implications and may limit the prognosis of cancer patients, as senescent cells, via their senescence associated secretory phenotype (SASP), can suppress anti-tumor immune responses and may increase the metastatic potential of non-senescent cancer cells. Preclinical data suggest that an eradication of senescent cells (senolytic therapies) or an application of SASP modulating therapies might improve the outcome of systemic cancer therapies, however, as a prerequisite to guide such approaches, robust and non-invasive modalities to visualize and quantify intratumoral senescence are needed. We recently reported on the safety evaluation of the novel Positron-Emission-Tomography (PET) tracer [18F]FPyGal, a radiolabeled substrate of senescence-associated ꞵ-galactosidase in healthy volunteers (AACR 2022, #7958). In summary, our data showed that the use of [18F]FPyGal is safe and well-tolerated in the described human study population. In the second stage of our trial, we are now investigating the concordance of histopathological senescence markers with [18F]FPyGal senescence signals in i) rectum cancer-, ii) non-small cell lung cancer- and iii) adenocarcinoma of the esophagogastric junction (AEG) patients, who are undergoing neoadjuvant therapy. Here, we report on patients from the rectum cancer cohort of the trial. [18F]FPyGal PET imaging was done before and after administration of neoadjuvant radiochemotherapy (RCTx). [18F]FPyGal PET signal was correlated with immunohistochemical senescence markers (p16, p21, p53) and quantification of SA-ß-gal (Senescence-associated beta-galactosidase) positive cells in biopsy materials (pre-therapy) and surgical resection materials (post-therapy). Expectedly, senescent cells were only detected at very low frequency in therapy naïve tumors and the lack of histological detection of senescence correlated with negativity in [18F]FPyGal imaging. In stark contrast, homogenous senescence, quantified with the indicated senescence markers, was detected in the majority of cancer cells after RCTx. Interestingly, in one rectum carcinoma, which underwent a full remission after RCTx, senescence of stroma cells in the area of the former tumor bed was detected by PET imaging and histologically. Collectively, our data indicate the utility of [18F]FPyGal PET imaging to non-invasively detect senescence. Future trials using [18F]FPyGal to guide oncological therapy, e.g. to apply senolytic drugs in a personalized manner, are warranted. Citation Format: Christian LaFougere, Brigitte Gueckel, Helmut Dittmann, Nils Trautwein, Martina Hinterleitner, Jonathan Cotton, Gerald Reischl, Gabriele Kienzle, Stephan Singer, Cihan Gani, Ulrich Lauer, Bernd Pichler, Lars Zender. Update: a phase 1/2, open-label study to assess safety, tolerability, biodistribution, radiation dosimetry and PET imaging characteristics of [18F]FPyGal in comparison to in-vitro diagnostic for the assessment of senescence in oncological patients (NCT04536454) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT095.

Aim/Introduction: Despite the spectacular success of immune checkpoint inhibitor therapy (ICT) in patients with metastatic cancer, only a limited proportion of patients benefit from ICT. An important gatekeeper for the therapeutic response to ICT are CD8+ cytotoxic T cells which are able to recognize MHC class I-dependent tumor antigens and destroy tumor cells. The radiolabeled minibody [89Zr]Zr-Df-IAB22M2C has a high affinity for human CD8+ T cells and was already successfully tested in a phase I study. Here, we aimed to gain first clinical PET/MRI experience with the non-invasive assessment of the CD8+ T cell distribution in cancer patients by in vivo [89Zr]Zr-Df-IAB22M2C.Material and Methods: We investigated 8 patients with metastasized cancers undergoing ICT. Radiolabeling of Df-IAB22M2C with Zr-89 was performed according to Good Manufacturing Practice. Multiparametric PET/MRI was acquired 24 h after injection of 74.2±17.9 MBq [89Zr]Zr-Df-IAB22M2C. We analyzed the [89Zr]Zr-Df-IAB22M2C uptake within the metastases and primary and secondary lymphatic organs. Results: [89Zr]Zr-Df-IAB22M2C injection was tolerated well without noticeable side effects. The CD8 PET/MRI data acquisitions 24 hours post administration of [89Zr]Zr-Df-IAB22M2C revealed a good image quality with a relatively low background signal due to only low unspecific tissue uptake and marginal blood pool retention. Only two metastatic lesions showed a markedly increased tracer uptake in our cohort of patients. Furthermore, we observed a high interpatient variability in the [89Zr]Zr-Df-IAB22M2C uptake within the primary and secondary lymphoid organs. Four out of five ICT patients exhibited a rather high [89Zr]Zr-Df-IAB22M2C uptake in the bone marrow. Two of these four patients as well as two other patients yielded a pronounced [89Zr]Zr-Df-IAB22M2C uptake within non metastatic lymph nodes. Interestingly, cancer progression in ICT patients was associated with a relatively low [89Zr]Zr-Df-IAB22M2C uptake in the spleen compared to the liver in 4 out of the 6 patients.Conclusion: Our first clinical experiences revealed the feasibility of [89Zr]Zr-Df-IAB22M2C PET/MRI to assess potential immune-related changes in the metastases and the primary and secondary lymphatic organs. According to our results, we hypothesize that alteration in the [89Zr]Zr-Df-IAB22M2C uptake in primary and secondary lymphoid organs might be associated with the response to ICT.

Psychedelic compounds have attracted increasing interest in recent years due to their therapeutic potential for psychiatric disorders. Methylenedioxymethamphetamine (MDMA) is currently being investigated in clinical trials to treat post-traumatic stress disorder. To understand the acute effects of psychedelic drugs in vivo, functional MR imaging (fMRI) has been widely used in recent years. Notably, fMRI studies have shown that MDMA leads to inhibition of brain activity, challenging earlier hypotheses indicating mainly excitatory effects. However, interpretation of hemodynamic changes induced by psychedelics is challenging because of the potent vascular effects associated with this class of substances. Therefore, this study aimed to investigate the acute effects of MDMA using simultaneous positron emission tomography (PET)/fMRI in rats. For this purpose, hemodynamic changes measured by BOLD-fMRI were related to alterations in glucose utilization and serotonin transporter (SERT) occupancy, investigated using [18F]FDG functional PET (fPET) and [11C]DASB PET.We demonstrate that MDMA induces global hemodynamic decreases accompanied by localized metabolic increases. Elevated metabolism was found primarily in limbic projection areas involved in emotion processing. Concurrent BOLD-fMRI decreases, also found in extracerebral areas, indicate that the BOLD-fMRI reductions observed in the brain are of vascular, non-neuronal origin. We further show that higher SERT occupancy strongly correlates with regional BOLD-fMRI reductions. Therefore, increased serotonin levels induced by SERT blockage may cause a neurovascular uncoupling.Correct understanding of the in vivo mechanism of MDMA not only supports ongoing research but also warrants a reassessment of previous studies on neuronal effects of psychedelics relying on neurovascular coupling.

The tumor-selective ganglioside antigene GD2 is frequently expressed on neuroblastomas and to a lesser extent on sarcomas and neuroendocrine tumors. The aim of our study was to evaluate the tumor targeting and biodistribution of (131)I-labeled chimeric GD2-antibody clone 14/18 ((131)I-GD2-ch14.18) in patients with late-stage disease in order to identify eligibility for radioimmunotherapy. Methods: Twenty patients (neuroblastoma, n = 9; sarcoma, n = 9; pheochromocytoma, n = 1; and neuroendocrine tumor, n = 1) were involved in this study. A 21- to 131-MBq dose (1–2 MBq/kg) of (131)I-GD2-ch14.18 (0.5–1.0 mg) was injected intravenously. Planar scintigraphy was performed within 1 h from injection (day 0) and on days 1, 2, 3, and 6 or 7 to analyze tumor uptake and tracer biodistribution. Serial blood samples were collected in 4 individuals. Absorbed dose to tumor lesions and organs was calculated using OLINDA software. Results: The tumor-targeting rate on a per-patient base was 65% (13/20), with 6 of 9 neuroblastomas showing uptake of (131)I-GD2-ch14.18. Tumor lesions showed maximum uptake at 20–64 h after injection (effective half-life in tumors, 33–192 h). The tumor-absorbed dose varied between 0.52 and 30.2 mGy/MBq (median, 9.08 mGy/MBq; n = 13). Visual analysis showed prominent blood-pool activity up to day 2 or 3 after injection. No pronounced uptake was observed in the bone marrow compartment or in the kidneys. Bone marrow dose was calculated at 0.09–0.18 mGy/MBq (median, 0.12 mGy/MBq), whereas blood dose was 1.1–4.7 mGy/MBq. Two patients (1 neuroblastoma and 1 pheochromocytoma) with particularly high tumor uptake underwent radioimmunotherapy using 2.3 and 2.9 GBq of (131)I-GD2-ch14.18, both achieving stable disease. Overall survival was 17 and 6 mo, respectively. Conclusion: (131)I-GD2-ch14.18 is cleared slowly from blood, not resulting in good tumor-to-background contrast until 2 d after application. With acceptable red marrow and organ dose, radioimmunotherapy is an option for patients with high tumor uptake. However, because of the variable GD2 expression, the decision should depend on pretherapeutic dosimetry.

BackgroundCyclotrons form a central infrastructure and are a resource of medical radionuclides for the development of new radiotracers as well as the production and supply of clinically established radiopharmaceuticals for patient care in nuclear medicine.AimTo provide an updated overview of the number and characteristics of cyclotrons that are currently in use within radiopharmaceutical sciences and for the development of radiopharmaceuticals to be used for patient care in Nuclear Medicine in Germany (D), Austria (A) and Switzerland (CH).MethodsPublicly available information on the cyclotron infrastructure was (i) consolidated and updated, (ii) supplemented by selective desktop research and, last but not least, (iii) validated by members of the committee of the academic “Working Group Radiochemistry and Radiopharmacy” (AGRR), consisting of radiochemists and radiopharmacists of the D-A-CH countries and belonging to the German Society of Nuclear Medicine (DGN), as well as the Radiopharmaceuticals Committee of the DGN.ResultsIn total, 42 cyclotrons were identified that are currently being operated for medical radionuclide production for imaging and therapy in Nuclear Medicine clinics, 32 of them in Germany, 4 in Austria and 6 in Switzerland. Two thirds of the cyclotrons reported (67%) are operated by universities, university hospitals or research institutions close to a university hospital, less by/in cooperation with industrial partners (29%) or a non-academic clinic/ PET-center (5%). Most of the cyclotrons (88%) are running with up to 18 MeV proton beams, which is sufficient for the production of the currently most common cyclotron-based radionuclides for PET imaging.DiscussionThe data presented provide an academically-updated overview of the medical cyclotrons operated for the production of radiopharmaceuticals and their use in Nuclear Medicine in the D-A-CH countries. In this context, we discuss current developments and trends with a view to the cyclotron infrastructure in these countries, with a specific focus on organizational aspects.

Tumor hypoxia is a major cause of resistance to radiochemotherapy in locally advanced head-and-neck cancer (LASCCHN). We present results of a randomized phase II trial on hypoxia dose escalation (DE) in LASCCHN based on dynamic [Patients with LASCCHN underwent baseline dynFMISO PET/CT. Hypoxic volumes (HV) were derived from dynFMISO data. Patients with hypoxic tumors (HV 0) were randomized into standard radiotherapy (ST: 70Gy/35fx) or dose escalation (DE: 77Gy/35fx) to the HV. Patients with non-hypoxic tumors were treated with ST. After a minimum follow-up of 2 years feasibility, acute/late toxicity and local control (LC) were analyzed.The study was closed prematurely due to slow accrual. Between 2009 and 2017, 53 patients were enrolled, 39 (74%) had hypoxic tumors and were randomized into ST or DE. For non-hypoxic patients, 100% 5-year LC was observed compared to 74% in patients with hypoxic tumors (p = 0.039). The difference in 5-year LC between DE (16/19) and ST (10/17) was 25%, p = 0.150. No relevant differences related to acute and late toxicities between the groups were observed.This study confirmed the prognostic value of hypoxia PET in LASCCHN for LC. Outcome after hypoxia DE appears promising and may support the concept of DE. Slow accrual and premature closure may partly be due to a high complexity of the study setup which needs to be considered for future multicenter trials.

Background: The diagnostic performance of [18F]fluoro-ethylcholine-PET-CT&amp, 4D-CT (FEC-PET&amp, 4D-CT) to identify parathyroid adenomas (PA) was analyzed when ultrasound (US) or MIBI-Scan (MS) failed to localize. Postsurgical one year follow-up data are presented. Methods: Patients in whom US and MS delivered either incongruent or entirely negative findings were subjected to FEC-PET&amp, 4D-CT and cases from July 2017 to June 2020 were analyzed, retrospectively. Cervical exploration with intraoperative PTH-monitoring (IO-PTH) was performed. Imaging results were correlated to intraoperative findings, and short term and one year postoperative follow-up data. Results: From July 2017 to June 2020 in 171 FEC-PET&amp, 4D-CTs 159 (92.9%) PAs were suggested. 147 patients already had surgery, FEC-PET&amp, 4D-CT accurately localized in 141, false neg. 4, false pos. 2, global sensitivity 0.97, accuracy 0.96, PPV 0.99. All of the 117 patients that already have completed their 12-month postoperative follow up had normal biochemical parameter, i.e., no signs of persisting disease. However, two cases may have a potential for recurrent disease, for a cure rate of at least 98.3%. Conclusion: FEC-PET&amp, 4D-CT shows unprecedented results regarding the accuracy localizing PAs. The one-year-follow-up data demonstrate a high cure rate. We, therefore, suggest FEC-PET-CT as the relevant diagnostic tool for the localization of PAs when US fails to localize PA, especially after previous surgery to the neck.

The catecholamine analogue [123 I]mIBG has been used for scintigraphic imaging of neuroblastoma since 1984. It is taken up by the noradrenaline transporter (NAT), which is present in most neuroblastoma cells. An alternative imaging method could be PET with 6-[18 F]fluorodopamine, which is also taken up by NAT, but-in contrast to mIBG-also by dopamine transporter (DAT), present in neuroblastoma cells (NAT > DAT). An enzymatic method was established allowing a rapid, quantitative transformation of FDOPA to FDA by DOPA decarboxylase within 25 minutes. This strategy was applied to [18 F]FDOPA, which was produced via nucleophilic synthesis (RCY 15%, 10 GBq, 50 GBq/μmol) and subsequently converted to [18 F]FDA (RCY 35%-50%, n = 5). Uptake and metabolism of FDOPA and FDA were analyzed in human Kelly and SK-N-SH neuroblastoma cell lines and in human Caki-1 kidney cells that can take up catecholamines and mIBG via an organic cation transporter (OCT). FDOPA and FDA were taken up by all three cells, but FDOPA could only be converted to FDA in neuroblastoma cells. As today, [18 F]FDOPA is well available in high yields, efficient enzymatic conversion to [18 F]FDA to be used for NAT/DAT PET imaging in neuroendocrine tumors is an attractive, alternative synthesis route.

Our purpose was to evaluate an imaging parameter–response relationship between the extent of tumor hypoxia quantified by dynamic 18F-fluoromisonidazole (18F-FMISO) PET/CT and the risk of relapse after radiotherapy in patients with head and neck cancer. Methods: Before a prospective cohort of 25 head and neck cancer patients started radiotherapy, they were examined with dynamic 18F-FMISO PET/CT 0–240 min after tracer injection. 18F-FMISO image parameters, including a hypoxia metric, MFMISO, derived from pharmacokinetic modeling of dynamic 18F-FMISO and maximum tumor-to-muscle ratio (TMRmax) at 4 h after injection, gross tumor volume (GTV), relative hypoxic volume based on MFMISO, and a logistic regression model combining GTV and TMRmax, were assessed and compared with a previous training cohort (n = 15). Dynamic 18F-FMISO was used to validate a tumor control probability model based on MFMISO. The prognostic potential with respect to local control of all potential parameters was validated using the concordance index for univariate Cox regression models determined from the training cohort, in addition to Kaplan–Meier analysis including the log-rank test. Results: The tumor control probability model was confirmed, indicating that dynamic 18F-FMISO allows stratification of patients into different risk groups according to radiotherapy outcome. In this study, MFMISO was the only parameter that was confirmed as prognostic in the independent validation cohort (concordance index, 0.71; P = 0.004). All other investigated parameters, such as TMRmax, GTV, relative hypoxic volume, and the combination of GTV and TMRmax, were not able to stratify patient groups according to outcome in this validation cohort (P = not statistically significant). Conclusion: In this study, the relationship between MFMISO and the risk of relapse was prospectively validated. The data support further evaluation and external validation of dynamic 18F-FMISO PET/CT as a promising method for patient stratification and hypoxia-based radiotherapy personalization, including dose painting.

Mitogen-activated protein kinase (MAPK) signaling plays an important role in inflammatory diseases such as rheumatoid arthritis (RA).The aim of our study was to elucidate the therapeutic potential of the highly selective p38 MAPK inhibitor Skepinone-L and the dual inhibitor LN 950 (p38 MAPK and JNK 3) in the K/BxN serum transfer model of RA. Additionally, we aimed to monitor MAPK treatment non-invasively in vivo using the hypoxia tracer [18F]fluoromisonidazole ([18F]FMISO) and positron emission tomography (PET). To induce experimental arthritis, we injected glucose-6-phosphate isomerase autoantibody-containing serum in BALB/c mice. MAPK inhibitor or Sham treatment was administered per os once daily. On days 3 and 6 after arthritis induction, we conducted PET imaging with [18F]FMISO. At the end of the experiment, ankles were harvested for histopathological analysis. Skepinone-L and LN 950 were applicable to suppress the severity of experimental arthritis confirmed by reduced ankle swelling and histopathological analysis. Skepinone-L (3.18 ± 0.19 mm) and LN 950 (3.40 ± 0.13 mm) treatment yielded a significantly reduced ankle thickness compared to Sham-treated mice (3.62 ± 0.11 mm) on day 5 after autoantibody transfer, a time-point characterized by severe arthritis. Hypoxia imaging with [18F]FMISO revealed non-conclusive results and might not be an appropriate tool to monitor MAPK therapy in experimental RA. Both the selective p38 MAPK inhibitor Skepinone-L and the dual (p38 MAPK and JNK 3) inhibitor LN 950 exhibited significant therapeutic effects during experimental arthritis. Thus, our study contributes to the ongoing discussion on the use of p38 MAPK as a potential target in RA.

Biochemical recurrence (BCR) after prostate cancer surgery is common, even after additional salvage radiotherapy. BCR might be explained by target miss. Improved diagnostic accuracy provided by PET could potentially circumvent this therapeutic gap. Therefore, we evaluated consecutive 68Ga-prostate-specific membrane antigen (PSMA) PET/CT, 11C-choline PET/CT, and standard CT imaging in the same patient with regard to TNM-stage migration and accordingly adapted curative radiotherapy options including ablative treatment of oligometastases (n ≤ 5). The cost efficacy of PET- versus CT-based treatment was also calculated. Methods: The prospective register database (064/2013BO1) was retrospectively searched for patients fulfilling the following 3 inclusion criteria: BCR after radical prostatectomy (pT2–pT4 pN0–pN1 cM0, postoperative radiotherapy allowed); 11C-choline PET/CT, 68Ga-PSMA PET/CT, and diagnostic CT performed within 24 h; and available clinical data. Ten treatment routines were defined according to current practice. Furthermore, intention-to-treat and treatment-related costs depending on the shift of TNM stage after imaging were analyzed. Eighty-three patients were eligible (median prostate-specific antigen level, 1.9 ng/mL). Results: Both PET examinations led to concordant results in 72% of patients, whereas the concordance of TNM staging between 68Ga-PSMA PET and diagnostic CT was only 36%. Incorrect staging would lead to “wrong” treatment and therefore to additional costs. A 68Ga-PSMA PET study would be cost-effective if additional costs do not exceed €3,844 ($4,312) (vs. CT). The number needed to image was 2 (for CT) and 4 (for 11C-choline PET) to avoid 1 incorrect treatment. In addition, 68Ga-PSMA PET staging enabled new curative options in half the patients with previous radiotherapy who otherwise receive palliative androgen deprivation therapy. Conclusion:68Ga-PSMA PET/CT is cost-effective in all patients with regard to avoidance of incorrect treatment. It enabled new curative options for patients with previous radiotherapy who are usually treated palliatively. Therefore, 68Ga-PSMA PET/CT staging should become standard for BCR after surgery with or without radiotherapy.

Although preclinical studies clearly indicate an effect of 5-HTTLPR genotype on 5-HT transporter (5-HTT) expression, studies in humans provided inconclusive results, hypothetically due to environmental factors and differences in individual behavior. For example, nicotine and other constituents of tobacco smoke elevate serotonin (5-HT) levels in the brain and may thereby cause homeostatic adaptations in 5-HTT availability that moderate effects of 5-HTTLPR genotype. To test whether 5-HTT availability in the midbrain is affected by smoking status and 5-HTTLPR genotype, we pooled data from prior studies on in vivo 5-HTT availability (BPND) measured with positron emission tomography (PET) and [11C]DASB. In total, we reanalyzed 5-HTT availability in 116 subjects using ANCOVA statistics. ROI analysis revealed that current smokers and non-smokers do not differ in midbrain BPND. Interestingly, smoking status significantly interacted with 5-HTTLPR genotype: active smoking was associated with reduced 5-HTT availability only in LL subjects but not in carriers of the S-allele. From the perspective of genotype effects, non-smokers showed the expected association with 5-HTTLPR, i.e. higher 5-HTT availability in LL subjects compared to carriers of the S-allele, whereas this pattern was actually reversed for active smokers. Our study indicates that smoking status moderates the association of 5-HTTLPR genotype and 5-HTT expression, which may help to explain inconsistent findings in previous studies. Regarding the mechanism, we suggest that smoking may induce epigenetic processes such as methylation of SLC6A4, which can differ depending on its genetic constitution.

Myeloid-derived suppressor cells (MDSCs) are immunosuppressive cells of the myeloid compartment and major players in the tumor microenvironment (TME). With increasing numbers of studies describing MDSC involvement in cancer immune escape, cancer metastasis and the dampening of immunotherapy responses, MDSCs are of high interest in current cancer therapy research. Although heavily investigated in the last decades, the in vivo migration dynamics of MDSC subpopulations in tumor- or metastases-bearing mice have not yet been studied extensively. Therefore, we have modified our previously reported intracellular cell labeling method and applied it to in vitro generated MDSCs for the quantitative in vivo monitoring of MDSC migration in primary and metastatic cancer. MDSC migration to primary cancers was further correlated to the frequency of endogenous MDSCs. Methods: Utilizing a 64Cu-labeled 1,4,7-triazacyclononane-triacetic acid (NOTA)-modified CD11b-specific monoclonal antibody (mAb) (clone M1/70), we were able to label in vitro generated polymorphonuclear (PMN-) and monocytic (M-) MDSCs for positron emission tomography (PET) imaging. Radiolabeled PMN- and M-MDSCs ([64Cu]PMN-MDSCs and [64Cu]M-MDSCs, respectively) were then adoptively transferred into primary and metastatic MMTV-PyMT-derived (PyMT-) breast cancer- and B16F10 melanoma-bearing experimental animals, and static PET and anatomical magnetic resonance (MR) images were acquired 3, 24 and 48 h post cell injection. Results: The internalization of the [64Cu]NOTA-mAb-CD11b-complex was completed within 3 h, providing moderately stable radiolabeling with little detrimental effect on cell viability and function as determined by Annexin-V staining and T cell suppression in flow cytometric assays. Further, we could non-invasively and quantitatively monitor the migration and tumor homing of both [64Cu]NOTA-αCD11b-mAb-labeled PMN- and M-MDSCs in mouse models of primary and metastatic breast cancer and melanoma by PET. We were able to visualize and quantify an increased migration of adoptively transferred [64Cu]M-MDSCs than [64Cu]PMN-MDSCs to primary breast cancer lesions. The frequency of endogenous MDSCs in the PyMT breast cancer and B16F10 melanoma model correlated to the uptake values of adoptively transferred MDSCs with higher frequencies of PMN- and M-MDSCs in the more aggressive B16F10 melanoma tumors. Moreover, aggressively growing melanomas and melanoma-metastatic lesions recruited higher percentages of both [64Cu]PMN- and [64Cu]M-MDSCs than primary and metastatic breast cancer lesions as early as 24 h post adoptive MDSC transfer, indicating an overall stronger recruitment of cancer-promoting immunosuppressive MDSCs. Conclusion: Targeting of the cell surface integrin CD11b with a radioactive mAb is feasible for labeling of murine MDSCs for PET imaging. Fast internalization of the [64Cu]NOTA-αCD11b-mAb provides presumably enhanced stability while cell viability and functionality was not significantly affected. Moreover, utilization of the CD11b-specific mAb allows for straightforward adaptation of the labeling approach for in vivo molecular imaging of other myeloid cells of interest in cancer therapy, including monocytes, macrophages or neutrophils.

CD8+ cytotoxic T cells are key players in anti-cancer immune responses as they destroy MHC class I-dependent tumor cells. Therefore, the spatial distribution of CD8+ cytotoxic T cells might represent an important surrogate for the response to cancer immunotherapy including immune checkpoint inhibitor therapy ICT. The radiolabeled minibody [89Zr]Zr-Df-IAB22M2C is characterized by a high affinity to human CD8 and was already investigated in a phase I study. Here, we present our first experience with the non invasive in vivo assessment of the whole body CD8 T cell distribution in cancer patients using clinical [89Zr]Zr-Df-IAB22M2C PET/MRI. In total 8 patients with metastasized cancers (5 x malignant melanoma; 1 x choroidal melanoma, 1 x NSCLC and 1 x sarcoma) were studied before (n = 3) or during (n = 5) ICT. Multiparametric PET/MRI was performed 24 h after injection of 74.2±17.9 MBq [89Zr]Zr-Df-IAB22M2C (1.1 - 1.8 mg Df-IAB22M2C) on a Siemens Biograph mMR System (SiemensHealthineers, Erlangen, Germany). The whole body distribution of the [89Zr]Zr-Df-IAB22M2C tracer was analyzed with a special focus on tumors/metastases as well as primary and secondary lymphatic organs. The PET tracer [89Zr]Zr-Df-IAB22M2C was well tolerated without any reported side effects. The PET/MRI acquisitions 24h p.i. of [89Zr]Zr-Df-IAB22M2C revealed a comparably low background signal with only a minor blood pool and unspecific tissue retention. Regarding the primary and secondary lymphoid organs we observed a high interpatient variability of the tracer uptake. Four out of five patients with previous ICT exhibited a relatively high [89Zr]Zr-Df-IAB22M2C uptake in the bone marrow. Also a large number of non metastatic lymph nodes yielded a pronounced [89Zr]Zr-Df-IAB22M2C uptake in four patients. Strikingly, a low [89Zr]Zr-Df-IAB22M2C uptake in the spleen compared to the liver (liver/spleen ratio < 10) was observed in 4 out of the 5 patients with cancer progression during ICT. Interestingly, only one metastasis with an intense tracer was detected in this patient cohort. This first clinical experiences revealed the feasibility to assess potential immune-related changes by [89Zr]Zr-Df-IAB22M2C PET/MRI. Considering these results we hypothesize that the whole body distribution of CD8+ cytotoxic T-cells assessed by non-invasive in vivo [89Zr]Zr-Df-IAB22M2C PET/MRI might be associated with the response to cancer immunotherapy which needs to be investigated in subsequent prospective trials. Citation Format: Johannes Schwenck, Dominik Sonanini, Walter Ehrlichmann, Gabriele Kienzle, Gerald Reischl, Pascal Krezer, Ian Wilson, Ron Korn, Irene Gonzalez-Menendez, Leticia Quintanilla-Martinez, Ferdinand Seith, Andrea Forschner, Thomas Eigentler, Lars Zender, Martin Röcken, Bernd Pichler, Lukas Flatz, Manfred Kneilling, Christian la Fougere. Imaging of CD8+ cytotoxic T-cells by Zr-89-Df-IAB22M2C PET/MRI: First clinical experience in patients with metastatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB058.

It is well established that senescence of cancer cells can be induced by treatment with classical cytotoxic therapies but also by molecularly targeted therapies or immunotherapies, a phenomenon referred to as therapy induced senescence (TIS). Occurrence of intratumoral senescence harbors broad therapeutic implications and may limit the prognosis of cancer patients, as senescent cells, via their senescence associated secretory phenotype (SASP), can suppress anti-tumour immune responses and may increase the metastatic potential of non-senescent cancer cells. Preclinical data suggest that an eradication of senescent cells (senolytic therapies) or an application of SASP modulating therapies might improve the outcome of systemic cancer therapies, however, as a prerequisite to guide such approaches, robust and non-invasive modalities to visualize and quantify intratumoral senescence are needed. Here we report on the preclinical and clinical development of the novel Positron-Emission-Tomography (PET) tracer [18F]FPyGal, a radiolabeled substrate of senescence-associated ꞵ-galactosidase. After thorough preclinical characterization of [18F]FPyGal in mouse models of TIS, we conducted a phase I study (NCT04536454) to assess i) safety and tolerability of [18F]FPyGal (primary endpoints) and ii) to characterize dosimetry and pharmacokinetics (secondary endpoints) as well as possible regions of physiologically increased tracer uptake after i.v. injection of [18F]FPyGal (mean 372.5±9.6) MBq in eight male healthy volunteers (mean 35.0±9.6 y; range 26-53 y). No treatment related adverse events (trAEs) or severe adverse events (SAEs) were recorded. No abnormal findings or changes were noted on physical examinations, vital signs and pulse oximetry values. Except for a transient reduction in leukocyte and neutrophil counts (6 h p.i.) in one patient (12.5%), no other abnormal laboratory values were observed. The total body absorbed dose was 4.40±0.08 μGy/MBq, highest mean absorbed doses were found in the urinary bladder wall (81.55±1.06 μGy/MBq), kidneys (21.05±4.74 μGy/MBq) and heart wall (9.77±1.32 μGy/MBq). The normalized whole-body effective radiation dose was 8.09±0.17 μSv/MBq. Collectively, our data show that i) [18F]FPyGal can robustly detect intratumoral senescence in preclinical cancer mouse models and ii) that the use of [18F]FPyGal was safe and well-tolerated in the described human study population. Radiation exposure was low and comparable to other clinically available 18F-labelled PET-tracers. In a second stage of our phase I trial, we are currently correlating [18F]FPyGal PET signals with histopathological senescence markers in human cancer patients. Citation Format: Christian LaFougere, Brigitte Gueckel, Helmut Dittmann, Martina Hinterleitner, Nils Trautwein, Jonathan Cotton, Gabriele Kienzle, Stephan Singer, Gerald Reischl, Ulrich Lauer, Bernd Pichler, Lars Zender. A phase 1/2, open-label study to assess safety, tolerability, biodistribution, radiation dosimetry and PET imaging characteristics of [18F]FPyGal in comparison to in-vitro diagnostic for the assessment of senescence in oncological patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT178.

ZusammenfassungRadiopharmaka, die mit Positronen-Emittern markiert sind, werden zumindest in Deutschland meist in Kliniken vor Ort hergestellt, die Nuklide stammen vom hauseigenen Zyklotron. Nur wenige dieser Radiopharmaka sind zugelassen und kommerziell erhältlich (wichtigstes Beispiel: 2-Deoxy-2-[18F]fluor-D-glucose, FDG). Syntheseprozesse sind komplexer und aufwendiger als Herstellungen aus zugelassenen Kits und Nukliden aus zugelassenen Generatoren. Auch die Anforderungen an die Qualitätskontrolle sind deutlich höher. Erfolgt die Herstellung unter einer offiziellen Herstellungserlaubnis, sind die Regeln der „Guten Herstellungspraxis“ (Good-Manufacturing-Praxis, GMP) anzuwenden. Auch die in Deutschland verbreitete Radiopharmaka-Herstellung unter Verantwortung eines Arztes (Arzneimittelgesetz, AMG § 13 2b) hat Qualitätsstandards zu genügen. GMP ist ein Qualitätssicherungs-System, das alle Aspekte der Herstellung betrachtet, um eine Gefährdung von Patienten durch das Arzneimittel zu minimieren. Für Räumlichkeiten, Ausrüstung, Personal, Produktion, Qualitätskontrolle, Umgang mit Produktmängeln, Inspektionen und Dokumentation sind formale Kriterien zu beachten. Qualifizierung und Validierung spielen dabei eine fundamentale Rolle. Die Herstellung hat in Räumen der Reinraumklasse C zu erfolgen, Abfüllung und Aufteilung in Klasse A. Hohe Investitionen und hoher Herstellungsaufwand rechtfertigen sich jedoch durch die stetig wachsende Bedeutung der Positronen-Emissions-Tomografie (PET) als bildgebender Diagnostik im Rahmen der Individualisierung therapeutischer Verfahren.

The staging and local management of breast cancer involves the evaluation of the extent and completeness of excision of both the invasive carcinoma component and also the intraductal component or ductal carcinoma in situ. When both invasive ductal carcinoma and coincident ductal carcinoma in situ are present, assessment of the extent and localization of both components is required for optimal therapeutic planning. We have used a mouse model of breast cancer to evaluate the feasibility of applying molecular imaging to assess the local status of cancers in vivo. Multi-tracer positron emission tomography (PET) and magnetic resonance imaging (MRI) characterize the transition from premalignancy to invasive carcinoma. PET tracers for glucose consumption, membrane synthesis, and neoangiogenesis in combination with a Gaussian mixture model-based analysis reveal image-derived thresholds to separate the different stages within the whole-lesion. Autoradiography, histology, and quantitative image analysis of immunohistochemistry further corroborate our in vivo findings. Finally, clinical data further support our conclusions and demonstrate translational potential. In summary, this preclinical model provides a platform for characterizing multistep tumor progression and provides proof of concept that supports the utilization of advanced protocols for PET/MRI in clinical breast cancer imaging.