R. Hicks

Progressive Metabolic and Structural Cerebral Perturbations After Traumatic Brain Injury: An In Vivo Imaging Study in the Rat

Traumatic brain injury (TBI) has a high incidence of long-term neurologic and neuropsychiatric morbidity. Metabolic and structural changes in rat brains were assessed after TBI using serial 18F-FDG PET and 3-dimensional MRI in vivo. Methods: Rats underwent lateral fluid percussion injury (FPI; n = 16) or a sham procedure (n = 11). PET and MR images were acquired at 1 wk and at 1, 3, and 6 mo after injury. Morphologic changes were assessed using MRI-based regions of interest, and hippocampal shape changes were assessed with large-deformation high-dimensional mapping. Metabolic changes were assessed using region-of-interest analysis and statistical parametric mapping with the flexible factorial analysis. Anxiety-like behavior and learning were assessed at 1, 3, and 6 mo after injury. Results: PET analyses showed widespread hypometabolism in injured rats, in particular involving the ipsilateral cortex, hippocampus, and amygdalae, present at 1 wk after FPI, most prominent at 1 mo, and then decreasing. Compared with the sham group, rats in the FPI group had decreased structural volume which progressively increased over 3–6 mo, occurring in the ipsilateral cortex, hippocampus, and ventricles after FPI (P < 0.05). Large-deformation high-dimensional mapping showed evolving hippocampal shape changes across the 6 mo after FPI. Injured rats displayed increased anxiety-like behavior (P < 0.05), but there were no direct correlations between the severity of the behavior abnormalities and functional or structural imaging changes. Conclusion: In selected brain structures, FPI induces early hypometabolism and delayed progressive atrophic changes that are dynamic and continue to evolve for months. These findings have implications for the understanding of the pathophysiology and evolution of long-term neurologic morbidity following TBI, and indicate an extended window for targeted neuroprotective interventions.

Relationship of Hepatic Functional Imaging to Irinotecan Pharmacokinetics and Genetic Parameters of Drug Elimination

PURPOSE The marked variability of irinotecan (Ir) clearance warrants individualized dosing based on hepatic drug handling. The aims of this trial were to identify parameters from functional hepatic nuclear imaging (HNI) that correlate with (1) Ir pharmacology, and (2) single-nucleotide polymorphisms (SNPs) for the ABCB1 (P-glycoprotein) and UGT-1A1 genes, known to influence Ir handling. METHODS Patients underwent genotyping for ABCB1 SNPs and UTUGT-1A1*28 carriage and HNI with 99mTc-DIDA (acetanilidoiminodiacetic acid)/99mTc-DISIDA (disofenin) and MIBI (99mTc-sestamibi) scans, probes for biliary transport proteins ABCC1 and -2, and ABCB1 function. HNI data were analyzed by noncompartmental and deconvolutional analysis to provide hepatic extraction and biliary excretion parameters. Patients received Ir, fluorouracil, and folinic acid using a weekly x2, every-3-weeks schedule. Plasma was taken for Ir and SN-38 analysis on day 1, cycle 1. RESULTS Of the 21 patients accrued, Ir pharmacokinetics data were obtained from 16 patients. 99mTc-DIDA/DISIDA percent retention at 1 hour (1-hour RET) correlated to baseline serum bilirubin (P = .008). Both 99mTc-DIDA/DISIDA and MIBI 1-hour RET correlated with SN-38 area under the curve (AUC; P < .01). On multiple regression analysis, SN-38 AUC = -215 + 18.68 x bilirubin + 4.27 x MIBI 1-hour RET (P = .009, R2 = 44.2%). HNI parameters did not correlate with Ir toxicity or UGT1A1*28 carriage. MIBI excretion was prolonged in patients with the ABCB1 exon 26 TT variant allele relative to wild-type (P = .015). CONCLUSION Functional imaging of hepatic uptake and excretory pathways may have potential to predict Ir pharmacokinetics. Evaluation of a larger cohort as well as polymorphisms in other biliary transporters and UGT1A1 alleles is warranted.

Immune response to RB1-regulated senescence limits radiation-induced osteosarcoma formation

Ionizing radiation (IR) and germline mutations in the retinoblastoma tumor suppressor gene (RB1) are the strongest risk factors for developing osteosarcoma. Recapitulating the human predisposition, we found that Rb1+/- mice exhibited accelerated development of IR-induced osteosarcoma, with a latency of 39 weeks. Initial exposure of osteoblasts to carcinogenic doses of IR in vitro and in vivo induced RB1-dependent senescence and the expression of a panel of proteins known as senescence-associated secretory phenotype (SASP), dominated by IL-6. RB1 expression closely correlated with that of the SASP cassette in human osteosarcomas, and low expression of both RB1 and the SASP genes was associated with poor prognosis. In vivo, IL-6 was required for IR-induced senescence, which elicited NKT cell infiltration and a host inflammatory response. Mice lacking IL-6 or NKT cells had accelerated development of IR-induced osteosarcomas. These data elucidate an important link between senescence, which is a cell-autonomous tumor suppressor response, and the activation of host-dependent cancer immunosurveillance. Our findings indicate that overcoming the immune response to senescence is a rate-limiting step in the formation of IR-induced osteosarcoma.

Role of 18 FDG-positron Emission Tomography Scanning in the Management of Histiocytosis

Diagnostic evaluation of histiocytic malignancies often involves a range of imaging studies to characterize skeletal and extraskeletal sites of involvement. Functional imaging with 18 FDG PET provides a potential method for non-invasively detecting active disease. We report two cases where this modality was positive and facilitated therapeutic monitoring.

Changes in hippocampal GABAA/cBZR density during limbic epileptogenesis: relationship to cell loss and mossy fibre sprouting.

Reduced GABA(A)/central benzodiazepine receptor (GABA(A)/cBZR) density, mossy fibre sprouting (MFS) and hippocampal cell loss are well described pathological features of human temporal lobe epilepsy (TLE), and animal models thereof. However, the temporal relationship of their development, and their roles in the emergence of the epilepsy, are uncertain. This was investigated in the kainic acid (KA)-induced post-status epilepticus (SE) model of TLE. Male Wistar rats (7 weeks, n=53) were randomised into control and KA groups. At 24h, 2, 4 or 6 weeks sham and KA post-SE animals were euthanised, brains extracted and GABA(A)/cBZR density, neuronal loss and MFS measured in hippocampal sub-regions. GABA(A)/cBZR density (B(max)) was measured by saturation-binding analysis using [(3)H]-flumazenil. At 24h post-SE GABA(A)/cBZR density was increased in almost all hippocampal subregions, but was decreased at the later time points with the exception of the dentate gyrus. There was significant neuronal loss in the CA3 SPc region (-24 ± 9.3%, p<0.05) at 24h, which remained stable at the later time points associated with an elevated GABA(A)/cBZR density per surviving neuron at 24h post-SE (+56.4%; p<0.05) which returned to control levels by 6 weeks post-SE. MFS in the dentate gyrus progressively increased over the 6 weeks following SE (+70.6% at 6 weeks), at which time there was a significant inverse relationship with GABA(A)/cBZR binding (r(2)=0.87; p=0.02). The temporal evolution of GABA(A)/cBZR density changes post-KA-induced SE, and the relationship with decreases in hippocampal pyramidal cell numbers and MFS, may point to a key role for these changes in the pathogenesis of acquired limbic epileptogenesis.

Antitumor Effect of Somatostatin Analogs in Neuroendocrine Tumors

TO THE EDITOR: We read with interest the report by Rinke et al 1 of the interim analysis of a randomized, placebo-controlled trial of octreotide LAR, the long-acting somatostatin analog (SSA), in metastatic midgut neuroendocrine tumors (NETs), along with the companion editorial by Oberg. 2 These results are an important contribution to our understanding of the biology of NETs. However, although scientifically provocative and supportive of the long-held belief of many clinicians in this field that SSAs have an antiproliferative effect in this heterogeneous group of diseases, the data published thus far still leave some important issues unresolved. The study planned to enroll 162 patients, but after nearly 8 years, only 85 were randomly assigned. Despite the much-reduced accrual, Rinke et al reported a marked difference in median time to progression on the basis of WHO radiologic criteria in the intent-to-treat population of 14.3 months with octreotide LAR compared with 6.0 months with placebo (hazard ratio [HR], 0.33; 95% CI, 0.20 to 0.59;P.000072). Importantly, similar benefits were demonstrated regardless of the presence or absence of carcinoid syndrome ( 40% of patients had carcinoid syndrome). As impressive as these results seem, we have concerns about whether both study arms are comparable. Notably, there was a highlystatisticallysignificantimbalanceinthetimesincediagnosis between the study arms in favor of the octreotide LAR arm, with a medianof7.5monthscomparedwith3.3monthsfortheplaceboarm (P.0096). Given the heterogeneous natural history of these tumors and the relatively small size of the analyzed population, it is unclear how this imbalance might have influenced the overall outcome of the study. A longer duration between diagnosis and treatment suggests more indolent disease; if by chance more of these patients were in the experimental treatment arm, as seems to have been the case in this trial, a longer time to progression could have ensued, whether or not the treatment was effective. Similarly, the planned subgroup analysis suggested that the benefit of octreotide LAR was greatest in patients withlimited(0%to10%)liverinvolvement(HR,0.17;95%CI,0.08to 0.40). Conceivably, those patients with a longer time since diagnosis were also those with limited liver involvement as a result of lower biologic aggressiveness. However, the explanation for the suggestion ofreducedactivityofoctreotideLARinthosepatientswithsignificant liver involvement in this trial was not discussed. If there is a proportionate increase in the overall quantity of somatostatin receptors with tumor bulk, the dose of octreotide LAR used may have been inade

Clinical influence of 18F-fluorodeoxyglucose positron emission tomography on the management of primary tumours of the thymus

The objective of the current study was to evaluate the effect of PET on the management of primary tumours of the thymus. Patients with a primary tumour of the thymus who underwent PET were identified from a prospective database. Forty‐three PET scans were carried out on 26 patients with primary thymic tumours. Sensitivity, specificity and accuracy were 79, 100 and 85%, respectively. Conventional imaging and PET findings were discordant in 10 cases (23%). PET appropriately changed patient management in three (7.0%) cases based on accurate results that differed from pre‐PET imaging. Most PET scans carried out (88%) did not influence clinical management. Patient comorbidities, limited treatment options and already planned surgery are factors that may hinder the effect of PET in the setting of thymic tumours. The potential for false‐negative results, probably because of a combination of low‐fluorodeoxyglucose avidity and small volume residual disease, needs to be considered in management planning. However, the positive predictive value of PET is high and enables appropriate modification of management in a small, but potentially important subset of patients.

Preliminary experience of 18F-fluorodeoxyglucose positron emission tomography in Castleman's disease

Castleman’s disease (CD) is a benign lymphoproliferative disorder with clinical manifestations that vary from asymptomatic discrete lymphadenopathy to widespread lymphadenopathy, hepatosplenomegaly and systemic symptoms. Two histological variants exist: hyaline vascular variant and plasma cell variant, the latter being more commonly associated with systemic symptoms. The disease can further be classified by the extent of involvement with ‘unicentric’ being applied to those cases with localized lymphadenopathy and ‘multicentric’ to those with disseminated disease. Multicentric disease is most often of plasma cell type and carries a higher risk of progression to lymphoma [1]. F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a functional imaging technique widely used in the management of a variety of malignant diseases, including lymphoma. For both Hodgkin’s disease and non-Hodgkin’s lymphoma, it improves disease staging (upor down-staging disease) and response assessment, risk-stratifies patients for relapse post-treatment and, when compared to conventional imaging, can demonstrate early relapse [2 – 12]. By contrast to lymphoma, there is very little information in the literature regarding the use of FDG-PET in the context of CD. Four single cases have been reported in which abnormal soft tissue masses subsequently diagnosed pathologically as CD have demonstrated increased radiotracer uptake on FDG-PET imaging [1,13 – 15]. However, the role of FDG-PET in the specific clinical settings of staging, response assessment and relapse surveillance of CD has not been investigated to our knowledge. Here, we present a small case series describing our own experience of FDG-PET as an imaging modality in six patients with CD. The patients were identified by screening the Diagnostic Imaging databases located at Peter MacCallum Cancer Centre, Melbourne and Moorabbin Hospital, Melbourne for cases of CD in which FDG-PET imaging had been performed between January 2000 and August 2005. All six patients had undergone FDG-PET imaging as part of staging or follow-up (Table I) whereas two of the six had an FDG-PET scan to assess response to treatment. FDG-PET imaging indicated unicentric mediastinal CD in two of our six patients (patients 1 and 2) by lack of demonstration of FDG-avidity at other nodal sites observed on computed tomography (CT). All questionable nodal sites on CT were less than 2 cm in diameter. Although the discordant CT and PET findings were not investigated further in either patient by biopsy, we feel that on balance these are unlikely to represent active disease. This opinion is based on the apparent spontaneous regression of one site (inguinal lymphadenopathy, patient 1, Figure 1A) and the stability of the CT appearances of two other sites (axillary node, patient 1, Figure 1a;

Abstract CT238: Phase I safety and biodistribution study of 124I-PEG-AVP0458 diabody in patients with TAG-72 positive ovarian and prostate cancer

Background: The development of antibody therapeutics for imaging and payload delivery is complex, and intact IgG have long half-lives that impact on tumor:blood ratios and tumor penetrance. Smaller molecular weight antibody constructs (eg diabodies) have been developed for improved penetrance into tumor, faster blood clearance, and enhanced tumor: normal tissue uptake, however renal uptake may impact on imaging and therapeutic effects. Through a novel pegylation strategy to surface disulphides, a diabody to TAG-72 (AVP0458) has been generated, and produced under cGMP for a first-in-human clinical trial. Materials and Methods: We have conducted a phase I, open label, first-in-human trial of PEG-AVP0458. The primary study objective was the safety of single dose of I-124 PEG-AVP0458 in patients (pts) with TAG-72 +ve relapsed / metastatic prostate or ovarian cancer. Secondary study objectives were evaluation of the biodistribution, tumor targeting, pharmacokinetics (PK) and immunogenicity of I-124 PEG-AVP0458. Pts were infused with I-124 PEG-AVP0458 (3-5mCi) at one of two dose levels (1mg/m 2 and 10mg/m 2 ), and imaged sequentially over a one week period. Safety, PK, and immunogenicity was assessed up to 30 days post infusion. Results: Six pts (1F:5M; age range 62-85yrs; 1 ovarian cancer, 5 prostate cancer) were entered into the study, 3 at each dose level. I-124 PEG-AVP0458 was well tolerated, with no infusion-related adverse events, and no serious adverse events observed. There was consistent biodistribution on PET imaging of I-124 PEG-AVP0458, with no normal tissue uptake. High tumor uptake was evident in metastatic disease in liver and lymph nodes, with lesion uptake seen within 1-2 days post injection. PK analysis showed a T½β of 46.8 ± 12.4 hrs. There was no impact of protein dose on biodistribution, tumor uptake or PK. No immunogenicity to PEG-AVP0458 was evident. Conclusions: I-124 PEG-AVP0458 is safe, and demonstrates excellent, rapid targeting of tumor in vivo, with no specific normal organ uptake, and high tumor: blood ratios. This data demonstrates the feasibility of using pegylated diabodies for imaging and for delivery of radioisotopes (RIT) or cytotoxic drug payloads (ADC) in cancer patients. Citation Format: Andrew M. Scott, Timothy Akhurst, Fook-Thean Lee, Marika Ciprotti, Ian Davis, Andrew Weickhardt, Hui Gan, Pece Kocovski, Nancy Guo, Linda Mileshkin, Scott Williams, Declan Murphy, Rod Hicks, Kunthi Pathmaraj, Sze Ting Lee, Graeme O9Keefe, Sylvia Gong, Maggie Oh, Michael Wheatcroft, Peter J. Hudson. Phase I safety and biodistribution study of 124I-PEG-AVP0458 diabody in patients with TAG-72 positive ovarian and prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT238. doi:10.1158/1538-7445.AM2015-CT238

Abstract 3484: In vivo activity of combined PI3k/mTOR and MEK-inhibition in a K-RASG12D; PTEN deletion mouse model of ovarian cancer

The PI3K/Akt pathway is commonly deregulated in human cancer, making it an attractive target for novel anti-cancer therapeutics. We have utilized a mouse model of ovarian cancer generated by K-RAS G12D activation and PTEN deletion in the ovarian surface epithelium (Dinulescu, et al, 2005) for the pre-clinical assessment of a novel PI3K/mTOR inhibitor (PF-04691502, Pfizer). To enable high throughput studies, we have transplanted primary tumours from these mice orthotopically into the ovarian bursa. Tumour growth rates were monitored by small animal-Ultrasound, and when tumours reached an average of 200mm 3 , mice received vehicle or 10mg/kg PF-04691502 daily for 7 days. Ultrasound and FDG-PET scans were performed on day 0, day 2 and day 7 of therapy. PF-04691502 inhibited tumour growth at 7 days by 71.64%±8.93. Tumour weights measured post-mortem following 7 days treatment also showed a significant decrease in tumour mass in treated mice (0.78±0.13g in vehicle treated versus 0.38±0.06g in drug treated mice; p PF-04691502 was sufficient to inhibit PI3K/mTOR resulting in inhibition of tumour growth; however, we did not observe tumour regression in this model. Notably, tumours from PF-04691502 treated mice displayed activation of pERK, suggesting that activation of the MAPK pathway is a mechanism by which KRAS-mutant tumours can limit the efficacy of PI3K/mTOR inhibitors alone. To overcome the effects of RAS/MAPK signalling, we have performed studies evaluating PF-04691502 (7.5mg/kg, daily) in combination with an inhibitor of MEK (PD-0325901, Pfizer, 10mg/kg, daily). Ultrasound monitoring of tumour volume shows that over a 7 day treatment period, PF-04691502 led to tumour growth inhibition of 55%±10.27, PD-0325901 alone led to tumour regression (36.3%±20.45) and combined PD-0325901 and PF-04691502 led to a striking tumour regression of 80.7%±4.97. These data show that combined inhibition of PI3K/mTOR and MEK converts tumor growth delay with PI3K-inhibition alone to tumour regression in this KRAS and PTEN mutant mouse model of ovarian cancer. Therefore inhibition of MEK may enhance activity of PI3K/mTOR-inhibitors in tumours showing activation of the PI3K pathway by genomic changes such as mutation in KRAS combined with loss of PTEN. Dinulescu D. M., et al. (2005) Nat. Med. 11:63-70. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3484.