An experimental approach to improve the Monte Carlo modelling of offline PET/CT-imaging of positron emitters induced by scanned proton beams

We report on the experimental campaign carried out at the Heidelberg Ion-Beam Therapy Center (HIT) to optimize the Monte Carlo (MC) modelling of proton-induced positron-emitter production. The presented experimental strategy constitutes a pragmatic inverse approach to overcome the known uncertainties in the modelling of positron-emitter production due to the lack of reliable cross-section data for the relevant therapeutic energy range. This work is motivated by the clinical implementation of offline PET/CT-based treatment verification at our facility. Here, the irradiation induced tissue activation in the patient is monitored shortly after the treatment delivery by means of a commercial PET/CT scanner and compared to a MC simulated activity expectation, derived under the assumption of a correct treatment delivery. At HIT, the MC particle transport and interaction code FLUKA is used for the simulation of the expected positron-emitter yield. For this particular application, the code is coupled to externally provided cross-section data of several proton-induced reactions. Studying experimentally the positron-emitting radionuclide yield in homogeneous phantoms provides access to the fundamental production channels. Therefore, five different materials have been irradiated by monoenergetic proton pencil beams at various energies and the induced β(+) activity subsequently acquired with a commercial full-ring PET/CT scanner. With the analysis of dynamically reconstructed PET images, we are able to determine separately the spatial distribution of different radionuclide concentrations at the starting time of the PET scan. The laterally integrated radionuclide yields in depth are used to tune the input cross-section data such that the impact of both the physical production and the imaging process on the various positron-emitter yields is reproduced. The resulting cross-section data sets allow to model the absolute level of measured β(+) activity induced in the investigated targets within a few per cent. Moreover, the simulated distal activity fall-off positions, representing the central quantity for treatment monitoring in terms of beam range verification, are found to agree within 0.6 mm with the measurements at different initial beam energies in both homogeneous and heterogeneous targets.

Heralded photonic interaction between distant single ions

We establish a heralded interaction between two remotely trapped single (40)Ca(+) ions through the exchange of single photons. In the sender ion, we release single photons with a controlled temporal shape on the P(3/2) to D(5/2) transition and transmit them to the distant receiver ion. Individual absorption events in the receiver ion are detected by quantum jumps. For continuously generated photons, the absorption reduces significantly the lifetime of the long-lived D(5/2) state. For triggered single-photon transmission, we observe a coincidence between the emission at the sender and quantum jump events at the receiver.

Clinicopathological differences between breast cancer in patients with primary metastatic disease and those without: a multicentre study

OBJECTIVE

Approximately 6% of breast cancer (BC) patients present with primary metastatic disease (pmBC) at first diagnosis. The clinicopathological differences between tumours from patients who have metastatic disease and those who do not are unclear.

METHODS

This study was an exploratory analysis of patients with pmBC treated in 8 German breast cancer centres between 1998 and 2010. Phenotypes were defined using the following immunohistochemical markers: oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (Her2). The control arm included the group of patients who had neither local recurrence nor distant metastases at a follow-up of at least 30 months after initial diagnosis.

RESULTS

A total of 2214 patients were included. Of these, 1642 had non metastatic BC, and 572 had pmBC. Eighty-five patients (15%) with pmBC were diagnosed at stage T1. On multivariate analysis, factors associated with pmBC were as follows: positive lymph node status, grade 3, lobular histology and Luminal B phenotype (Her 2 positive). Of the sample, 197 patients (34%) with pmBC were diagnosed as stage T2, 90 patients (16%) were diagnosed as stage T3, and 200 patients (35%) were diagnosed as stage T4. Only positive lymph node status and grade 3 were reported as risk factors for distant metastases in patients with stage T3 and T4 cancer.

CONCLUSION

There are differences in the clinicopathological features among breast cancer patients with primary metastases and those without. Receptor expression and histological type play a minor role in the risk for metastasis in patients with stage T3 and T4 disease when compared to patients with T1 pmBC tumours. On initial diagnosis, lobular histology and Luminal B positivity (Her 2 positive) in T1 pmBC were determined to be risk factors for primary metastatic disease.

Mitochondrion-derived reactive oxygen species lead to enhanced amyloid beta formation

AIMS

Intracellular amyloid beta (Aβ) oligomers and extracellular Aβ plaques are key players in the progression of sporadic Alzheimer's disease (AD). Still, the molecular signals triggering Aβ production are largely unclear. We asked whether mitochondrion-derived reactive oxygen species (ROS) are sufficient to increase Aβ generation and thereby initiate a vicious cycle further impairing mitochondrial function.

RESULTS

Complex I and III dysfunction was induced in a cell model using the respiratory inhibitors rotenone and antimycin, resulting in mitochondrial dysfunction and enhanced ROS levels. Both treatments lead to elevated levels of Aβ. Presence of an antioxidant rescued mitochondrial function and reduced formation of Aβ, demonstrating that the observed effects depended on ROS. Conversely, cells overproducing Aβ showed impairment of mitochondrial function such as comprised mitochondrial respiration, strongly altered morphology, and reduced intracellular mobility of mitochondria. Again, the capability of these cells to generate Aβ was partly reduced by an antioxidant, indicating that Aβ formation was also ROS dependent. Moreover, mice with a genetic defect in complex I, or AD mice treated with a complex I inhibitor, showed enhanced Aβ levels in vivo.

INNOVATION

We show for the first time that mitochondrion-derived ROS are sufficient to trigger Aβ production in vitro and in vivo.

CONCLUSION

Several lines of evidence show that mitochondrion-derived ROS result in enhanced amyloidogenic amyloid precursor protein processing, and that Aβ itself leads to mitochondrial dysfunction and increased ROS levels. We propose that starting from mitochondrial dysfunction a vicious cycle is triggered that contributes to the pathogenesis of sporadic AD.

Parameters for calcium metabolism in women with polycystic ovary syndrome who undergo clomiphene citrate stimulation: a prospective cohort study

OBJECTIVE

To evaluate whether parameters for calcium metabolism were associated with characteristics of polycystic ovary syndrome (PCOS).

DESIGN

A prospective cohort study.

METHODS

Ninety-one anovulatory, infertile women with PCOS patients underwent clomiphene citrate (CC) stimulation. Main outcome measures were parathyroid hormone (PTH); 25-hydroxyvitamin D3 (25OHD3); serum levels of calcium, phosphorus, magnesium, albumin, and total protein; the serum calcium-phosphorus product; LH; FSH; sexual hormone binding globulin; testosterone; and androstenedione.

RESULTS

PTH correlated inversely with serum calcium (r=-0.235; P=0.004) and 25OHD3 (r=-0.664; P<0.001), whereas positive correlations were found between PTH and body mass index (BMI; r=0.270; P=0.010) and between PTH and testosterone (r=0.347; P=0.001). After stimulation with 50 mg CC, 57.1% (52/91) developed a follicle, whereas 26.4% (24/91) became pregnant. In a multivariate model to predict both follicle development and pregnancy, BMI and 25OHD3 deficiency were significant predictive parameters.

CONCLUSIONS

25OHD3 deficiency was an independent predictive parameter of CC stimulation outcome, in terms of follicle development and pregnancy. Our results suggest a substantial role of vitamin D in PCOS and infertility treatment in these patients.

Monitoring of patients treated with particle therapy using positron-emission-tomography (PET): the MIRANDA study

BACKGROUND

The purpose of this clinical study is to investigate the clinical feasibility and effectiveness of offline Positron-Emission-Tomography (PET) quality assurance for promoting the accuracy of proton and carbon ion beam therapy.

METHODS/DESIGN

A total of 240 patients will be recruited, evenly sampled among different analysis groups including tumors of the brain, skull base, head and neck region, upper gastrointestinal tract including the liver, lower gastrointestinal tract, prostate and pelvic region. From the comparison of the measured activity with the planned dose and its corresponding simulated activity distribution, conclusions on the delivered treatment will be inferred and, in case of significant deviations, correction strategies will be elaborated.

DISCUSSION

The investigated patients are expected to benefit from this study, since in case of detected deviations between planned and actual treatment delivery a proper intervention (e.g., correction) could be performed in a subsequent irradiation fraction. In this way, an overall better treatment could be achieved than without any in-vivo verification. Moreover, site-specific patient-population information on the precision of the ion range at HIT might enable improvement of the CT-range calibration curve as well as safe reduction of the treatment margins to promote enhanced treatment plan conformality and dose escalation for full clinical exploitation of the promises of ion beam therapy.

TRIAL REGISTRATION

NCT01528670.

P4-10-07: Clinico-Pathologic Features of Breast Cancer Patients with Primary Metastatic Disease Versus Localized Disease: A Multicenter Study

Objective: Approximately 6% of breast cancer patients present with primary metastatic disease (pmBC) at first diagnosis. Clinicopathological differences to non-metastatic patients are undetermined.

Methods: Exploratory analysis of patients with pmBC treated in 8 breast cancer units between 1998 and 2010. Tumor characteristics of these patients were compared with non-metastatic breast cancer patients (BC) of one breast cancer center who had neither local-recurrence nor distant metastases during 30 months of follow-up after first diagnosis. Standard staging in patients with first diagnosis of BC included chest X-ray, abdominal ultrasonography and bone scan. Molecular subtypes were analyzed and defined by immunohistochemical markers (ER, PR, Her2-receptor).

Results: 2.214 patients were included, 1.642 with BC and 572 with pmBC, respectively. Patients with pmBC were 7 years older (BC 58 years of age vs. pmBC 65 years; p=0.000) and were more likely to be postmenopausal (74% vs. 83%; p=0.000). Most common localizations of distant first metastases were bone (61,5%), liver (24%), lung (21%) and non-axillary lymph nodes (12%).

85 (15%) patients with pmBC were diagnosed in stage T1. Factors associated with pmBC in multivariate analysis for this group were positive lymph node status (OR 3.4; 95%CI 2.3−6.0; p=0.000), grading 3 (OR 2.3; 95%CI 1.3−4.0; p=0.003), lobular histology (OR 2.3; 95%CI 1.2−4.5; p=0,010) and phenotype Luminal B (OR 2.4; 95%CI 1.25−5.0; p=0.014). 197 (34%) patients with pmBC were diagnosed in stage T2; positive lymph node status (OR 4.8; 95%CI 1.1−3.0; p=0.017) and grading 3 (OR 1.6; 95% CI 1.6−2.3; p=0.019) were reported as risk factors for this group. 90 (16%) and 200 (35%) patients were diagnosed with stages T3 and T4, respectively. In T3/4 tumors a positive lymph node status (OR 5.2; 95% CI 2.9−9.3; p=0.000) and grading 3 (OR 2.2; 95%CI 1.2−3.9; p=0.009) could be defined as significant risk factors for distant metastases. Postmenopausal status was associated with primary metastases in stage T2 (OR 1.8; 95%CI 1.2−2.9; p=0.008) and T3/4 (OR 2.4; 95%CI 1.2−4.7; p=0.011) but not in T1 tumors (OR 1.3; 95%CI 0.7−2.1; p=0.420). There was no association with hormone or Her2 receptor status nor with a specific phenotype for T2-4 tumors.

Conclusion: The clinico-pathological features of breast cancer patients with or without primary metastases differ. In all stages positive lymph node status and higher grading were associated with pmBC significantly. Lobular histology was reported as a risk factor for T1-2 compared to patients without metastases. This feature was not found for T3/4 pmBC. T1 pmBC were likely to be associated with luminal B phenotype. T3-4 pmBC have not been associated with any phenotype or hormone receptor constellation as risk factor for metastases. Tumor biology seems to play a minor role for risk of metastases in T3-4 stages compared to patients with T1-tumors. Findings from this analysis should be considered in the choice of staging methods, especially in stage T1.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-10-07.