Immune Response to Molecular Radiotherapy with 177Lu-DOTATOC: Predictive Value of Blood Cell Counts for Therapy Outcome.

Purpose: In a prior, retrospective study, 76% of patients with advanced neuroendocrine tumors undergoing 177Lu-DOTATOC molecular radiotherapy (MRT) showed their best response within 8 months from the first MRT cycle. In 24% of patients, latency was much greater up to >22 months after the first cycle, and long after near-complete decay of 177Lu from the last cycle. An immune response induced by MRT seems a likely explanation. As a crude measure of immunocompetence, the authors investigated whether blood cell counts (BCCs) may have predictive value for MRT outcome with 177Lu-DOTATOC. Methods: 56 Patients with neuroendocrine tumors (NET) were administered 177Lu-DOTATOC (mean 2.1 cycles; range 1-4) with median radioactivity of 7.0 GBq/cycle at 3-month intervals. Patients' BCCs were evaluated for four responder categories: CR, PR, SD, and PD (RECIST 1.1). Furthermore, baseline BCCs were correlated with progression-free survival (PFS). Finally, BCCs of patients with (PMT+) and without prior medical therapy (PMT-) were compared. Results: Significant differences between responder categories were found for baseline hemoglobin (Hb), erythrocytes, neutrophils, lymphocytes, neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and LEHN-score, integrating lymphocyte, erythrocyte, and neutrophil counts, and Hb level, but not for leukocytes and platelets. LEHN-score yielded an almost complete separation between CR and PD groups. In analogy, PFS times showed significant correlations with baseline Hb, erythrocytes, neutrophils, lymphocytes, NLR, PLR, and LEHN-score, the LEHN-score showing the strongest correlation, but not with leukocytes and platelets. For PMT- patients, median PFS was 34.5 months, compared with 20.8 months in PMT+ patients, with corresponding baseline lymphocyte (32.1 ± 9.6% vs. 24.5 ± 11.6%, p = 0.028) and neutrophil (54.9 ± 11.6% vs. 63.5 ± 13.7%, p = 0.039) counts. Conclusion: These findings emphasize the significance of an immune response to MRT for obtaining optimal therapy efficacy and support concepts to enhance the immune response of less immunocompetent patients before MRT. It seems advisable to avoid prior or concomitant immunosuppressant medical therapy.

Safety and Efficacy of Para-Aminohippurate Coinfusion for Renal Protection During Peptide Receptor Radiotherapy in Patients with Neuroendocrine Tumors.

Para-aminohippurate, also known as p-aminohippuric acid (PAH), is used clinically to measure effective renal plasma flow. Preclinically, it was shown to reduce 177Lu-DOTATOC uptake in the kidneys while improving bioavailability compared with amino acid (AA) coinfusion. We report the safety and efficacy of PAH coinfusion during peptide receptor radiotherapy in patients with neuroendocrine tumors. Methods: Twelve patients with metastatic or unresectable gastroenteropancreatic neuroendocrine tumors received 177Lu-DOTATOC in 33 treatment cycles. Either 8 g of PAH or a mixture of 25 g of arginine and 25 g of lysine were coinfused. Safety was assessed by monitoring laboratory data, including hematologic and renal data, as well as electrolytes obtained before and 24 h after treatment. For radiation dosimetry, whole-body scans were performed at 1, 24, and 48 h and a SPECT/CT scan was performed at 48 h, along with blood sampling at 5 min and 0.5, 2, 4, 24, and 48 h after administration. Absorbed dose estimations for the kidneys and bone marrow were performed according to the MIRD concept. Results: In 15 treatment cycles, PAH was coinfused. No changes in mean creatinine level, glomerular filtration rate, and serum electrolytes were observed before or 24 h after treatment when using PAH protection (P ≥ 0.20), whereas serum chloride and serum phosphate increased significantly under AA (both P < 0.01). Kidney-absorbed dose coefficients were 0.60 ± 0.14 Gy/GBq with PAH and 0.53 ± 0.16 Gy/GBq with AA. Based on extrapolated cumulative kidney-absorbed doses for 4 cycles, 1 patient with PAH protection and 1 patient with AA protection in our patient group would exceed the 23-Gy conservative threshold. The bone marrow-absorbed dose coefficient was 0.012 ± 0.004 Gy/GBq with PAH and 0.012 ± 0.003 Gy/GBq with AA. Conclusion: PAH is a promising alternative to AA for renal protection during peptide receptor radiotherapy. Further research is required to systematically investigate the safety profile and radiation dosimetry at varying PAH plasma concentrations.

[(177)Lu-DOTA](0)-D-Phe(1)-Tyr(3)-Octreotide ((177)Lu-DOTATOC) For Peptide Receptor Radiotherapy in Patients with Advanced Neuroendocrine Tumours: A Phase-II Study.

PURPOSE: To characterise efficacy and safety of (177)Lu-DOTATOC as agent for peptide receptor radiotherapy (PRRT) of advanced neuroendocrine tumours (NET). PATIENTS AND METHODS: Fifty-six subjects with metastasized and progressive NET (50% gastroenteral, 26.8% pancreatic, 23.2% other primary sites) treated consecutively with (177)Lu-DOTATOC were analysed retrospectively. Subjects were administered (177)Lu-DOTATOC (mean 2.1 cycles; range 1-4) as 7.0GBq (median) doses at three-monthly intervals. Efficacy was analysed using CT and/or MRI according to RECIST 1.1 criteria and results were stratified for the number of administered cycles and the primary tumour origin. RESULTS: In the total NET population (A), median progression-free (PFS) and overall survival (OS) were 17.4 and 34.2 months, respectively, assessed in a follow-up time (mean ± SD) of 16.1 ± 12.4 months. In patients receiving more than one cycle, mean follow-up time was 22.4 ± 11.0 months for all NETs (B) and PFS was 32.0 months for all NETs (B), 34.5 months for GEP-NET (C), and 11.9 months for other NETs (D). Objective response rates (Complete/Partial Responses) were 33.9%, 40.6%, 54.2%, and 0% for A, B, C, and D groups, respectively, while disease control rates in the same were 66.1%, 93.8%, 100%, and 75%. Complete responses (16.1%, 18.8% and 25.0% for groups A, B and C) were high, 78% of which were maintained throughout the follow up. There were no serious adverse events. One case of self-limiting grade 3 myelotoxicity was reported. Although 20% of patients had mild renal insufficiency at baseline, there was no evidence of exacerbated or de novo renal toxicity after treatment. CONCLUSION: (177)Lu-DOTATOC is a novel agent for PRRT with major potential to induce objective tumour responses and sustained disease control in progressive neuroendocrine tumours, even when administered in moderate activities. The observed safety profile suggests a particularly favourable therapeutic index, including in patients with impaired bone marrow or renal function, which reflects a uniquely low uptake of (177)Lu-DOTATOC by normal organs.

23Na chemical shift imaging and Gd enhancement of myocardial edema.

Myocardial edema can arise in several disease states. MRI contrast agent can accumulate in edematous tissue, which complicates differential diagnosis with contrast-enhanced (CE)-MRI and might lead to overestimation of infarct size. Sodium Chemical Shift Imaging ((23)Na-CSI) may provide an alternative for edema imaging. We have developed a non-infarct, isolated rat heart model with two levels of edema, which was studied with (23)Na-CSI and CE-MRI. In edematous, but viable tissue the extracellular sodium (Na (e) (+)) signal is hypothesized to increase, but not the intracellular sodium (Na (i) (+)) signal. Isolated hearts were perfused at 60 (n = 6) and 140 mmHg (n = 5). Dimethyl methylphosphonate (DMMP) and phenylphosphonate (PPA) were used to follow edema formation by (31)P-MR Spectroscopy. In separate groups, Thulium(III)1,4,7,10 tetraazacyclododecane-N,N',N″,N'''-tetra(methylenephosphonate) (TmDOTP(5-)) and Gadovist were used for (23)Na-CSI (n = 8) and CE-MRI (n = 6), respectively. PPA normalized signal intensity (SI) was higher at 140 versus 60 mmHg, with a ratio of 1.27 ± 0.12 (p < 0.05). The (DMMP-PPA)/dry weight ratio, as a marker of intracellular volume, remained unchanged. The mid-heart cross sectional area (CSA) of the left ventricle (LV) was significantly increased at 140 mmHg. In addition, at 140 mmHg, the LV Na (e) (+) SI increased with a 140 mmHg/60 mmHg ratio of 1.24 ± 0.18 (p < 0.05). Na (i) (+) SI remained essentially unchanged. With CE-MRI, a subendocardially enhanced CSA was identified, increasing from 0.20 ± 0.02 cm(2) at 60 mmHg to 0.31 ± 0.02 cm(2) at 140 mmHg (p < 0.05). Edema shows up in both CE-MRI and Na (e) (+) . High perfusion pressure causes more edema subendocardially than subepicardially. (23)Na-CSI is an attractive alternative for imaging of edema and is a promising tool to discriminate between edema, acute and chronic MI.

Quantitative T 2* assessment of acute and chronic myocardial ischemia/reperfusion injury in mice.

OBJECT: Imaging of myocardial infarct composition is essential to assess efficacy of emerging therapeutics. T (2) (*) mapping has the potential to image myocardial hemorrhage and fibrosis by virtue of its short T (2) (*) . We aimed to quantify T (2) (*) in acute and chronic myocardial ischemia/reperfusion (I/R) injury in mice. MATERIALS AND METHODS: I/R-injury was induced in C57BL/6 mice (n = 9). Sham-operated mice (n = 8) served as controls. MRI was performed at baseline, and 1, 7 and 28 days after surgery. MRI at 9.4 T consisted of Cine, T (2) (*) mapping and late-gadolinium-enhancement (LGE). Mice (n = 6) were histologically assessed for hemorrhage and collagen in the fibrotic scar. RESULTS: Baseline T (2) (*) values were 17.1 ± 2.0 ms. At day 1, LGE displayed a homogeneous infarct enhancement. T (2) (*) in infarct (12.0 ± 1.1 ms) and remote myocardium (13.9 ± 0.8 ms) was lower than at baseline. On days 7 and 28, LGE was heterogeneous. T (2) (*) in the infarct decreased to 7.9 ± 0.7 and 6.4 ± 0.7 ms, whereas T (2) (*) values in the remote myocardium were 14.2 ± 1.1 and 15.6 ± 1.0 ms. Histology revealed deposition of iron and collagen in parallel with decreased T (2) (*) . CONCLUSION: T (2) (*) values are dynamic during infarct development and decrease significantly during scar maturation. In the acute phase, T (2) (*) values in infarcted myocardium differ significantly from those in the chronic phase. T (2) (*) mapping was able to confirm the presence of a chronic infarction in cases where LGE was inconclusive. Hence, T (2) (*) may be used to discriminate between acute and chronic infarctions.

A view on imaging in drug research and development for respiratory diseases.

With the incidence of respiratory diseases increasing throughout the world, new therapies are needed. This review provides a short overview of different imaging techniques of interest for drug discovery and development within the pulmonary disease area. The focus is on studies performed in both animals and humans, which are of importance for understanding pathophysiological aspects and evaluating new drugs. Rather than emphasizing particular lung diseases, the noninvasive diagnosis and quantification of a number of characteristics related to several pathological conditions of the lung are addressed: inflammation, mucus secretion and clearance, emphysema, ventilation, perfusion, fibrosis, airway remodeling, and pulmonary arterial hypertension. Techniques are discussed based on their present use or potential future utilization in the context of drug studies.

Evaluation of infarcted murine heart function: comparison of prospectively triggered with self-gated MRI.

Measurement of cardiac function is often performed in mice after, for example, a myocardial infarction. Cardiac MRI is often used because it is noninvasive and provides high temporal and spatial resolution for the left and right ventricle. In animal cardiac MRI, the quality of the required electrocardiogram signal is variable and sometimes deteriorates over time, especially with infarcted hearts or cardiac hypertrophy. Therefore, we compared the self-gated IntraGateFLASH method with a prospectively triggered FLASH (fast low-angle shot) method in mice with myocardial infarcts (n = 16) and in control mice (n = 21). Mice with a myocardial infarct and control mice were imaged in a vertical 9.4-T MR system. Images of contiguous 1-mm slices were acquired from apex to base with prospective and self-gated methods. Data were processed to calculate cardiac function parameters for the left and right ventricle. The signal-to-noise and contrast-to-noise ratios were calculated in mid-ventricular slices. The signal-to-noise and contrast-to-noise ratios of the self-gated data were higher than those of the prospectively gated data. Differences between the two gating methods in the cardiac function parameters for both left and right ventricle (e.g. end-diastolic volumes) did not exceed the inter-observer variability in control or myocardial infarcted mice. Both methods gave comparable results with regard to the cardiac function parameters in both healthy control mice and mice with myocardial infarcts. Moreover, the self-gated method provided better signal-to-noise and contrast-to-noise ratios when the acquisition time was equal. In conclusion, the self-gated method is suitable for routine use in cardiac MRI in mice with myocardial infarcts as well as in control mice, and obviates the need for electrocardiogram triggering and respiratory gating. In both gating methods, more than 10 frames per cardiac cycle are recommended.

Characterization and in vitro and in vivo testing of CB2-receptor- and NGAL-targeted paramagnetic micelles for molecular MRI of vulnerable atherosclerotic plaque.

PURPOSE: Atherosclerotic plaque macrophages express the peripheral cannabinoid receptor (CB2-R) and promote fibrous cap degradation by secretion of neutrophil gelatinase-associated lipocalin 2 (NGAL). In this study, we report the preparation, characterization, and in vitro and in vivo testing of double-labeled (MR and fluorescent) CB2-R- and NGAL-targeted micelles. PROCEDURES/RESULTS: Specific CB2-R agonists or antibodies directed to 24p3 (mouse homolog of NGAL) were incorporated into di-oleoyl-polyethylene glycol-phosphatidylethanolamine 1000 (DOPE-PEG1000) micelles or di-stearoyl-polyethylene glycol-phosphatidylethanolamine 2000 (DSPE-PEG2000) micelles. The hydrodynamic diameter, determined by dynamic light scattering, was 16.5 and 19.0 nm for CB2-R-targeted DOPE-PEG1000 and DSPE-PEG2000 micelles, respectively, and 23.0 nm for Ab-conjugated DSPE-PEG2000 micelles. In vitro and in vivo MRI and fluorescence microscopy showed specific binding of CB2-R-targeted and 24p3-targeted micelles to in vitro systems and to aortic plaque in apoE(-/-)/eNOS(-/-) mice, respectively. CONCLUSIONS: CB2-R- and NGAL-targeted micelles show promise as tools for in vivo characterization of vulnerable plaque.

Recent developments and new perspectives on imaging of atherosclerotic plaque: role of anatomical, cellular and molecular MRI part III.

Atherosclerotic plaque disruption accounts for the major part of cardiovascular mortality and the risk of disruption appears to depend on plaque composition. Carotid plaques in patients, scheduled for endarterectomy, have been successfully characterised with MRI. MRI has the advantage of combining information about morphology and function. Unfortunately, the tortuosity and size of the coronary arteries, and the respiratory and cardiac motion hinder the in vivo characterisation of human coronary plaque. In addition to plaque composition several molecular markers of the different processes involved in atherosclerosis, such as integrins, matrix metalloproteinases and fibrin seem to correlate with risk of plaque rupture and clinical outcome. These molecular markers can be targeted with antibodies coupled to carriers, which are loaded with gadolinium for detection (molecular MRI). Several cellular/molecular MRI studies in animal models and some in human patients have been conducted with varying levels of success. The advent of clinical high field magnets, the development of contrast agent carriers with high relaxivity and the development of relatively new MR contrast techniques appear to be promising in the field of plaque imaging. Future MRI studies will have to focus on the molecular target of the atherosclerotic process, which has the highest prognostic value with regard to acute coronary syndromes and on the most suitable contrast agent to visualize that target.

Antioxidant treatment attenuates pulmonary arterial hypertension-induced heart failure.

ROS have been implicated in the development of pathological ventricular hypertrophy and the ensuing contractile dysfunction. Using the rat monocrotaline (MCT) model of pulmonary arterial hypertension (PAH), we recently reported oxidative stress in the failing right ventricle (RV) with no such stress in the left ventricle of the same hearts. We used the antioxidant EUK-134 to assess the role of ROS in the pathological remodeling and dysfunction of the RV. PAH was induced by an injection of MCT (80 mg/kg, day 0), treatment with EUK-134 (25 mg/kg, once every 2 days) of control and MCT-injected animals [congestive heart failure (CHF) group] was started on day 10, and animals were analyzed on day 22. EUK-134 treatment of the CHF group attenuated cardiomyocyte hypertrophy and associated changes in mRNA expression (myosin heavy chain-beta and deiodinase type 3). It also reduced RV oxidative stress and proapoptotic signaling and prevented interstitial fibrosis. Cardiac MRI showed that ROS scavenging did not affect the 37% increase in end-diastolic volume of the RV in the CHF relative to the control group, but the threefold increase in end-systolic volume was reduced by 42% in the EUK-134-treated CHF group. The improved systolic function was confirmed using echocardiography by an assessment of tricuspid annular plane systolic excursion. These data indicate an important role of ROS in RV cardiomyocyte hypertrophy and contractile dysfunction due to PAH and show the potential of EUK-class antioxidants as complementary therapeutics in the treatment of RV dysfunction in PAH.