Related Articles

Purpose

Evaluation and comparison of 3’-[18F]-fluoro-3’-deoxy-L-thymidine (FLT) and 2-[18F]-fluoro-2-deoxyglucose (FDG)-PET to monitor early response following both cyclophosphamide and temsirolimus treatment in a mouse model of Burkitt lymphoma.

Methods

Daudi xenograft mice were treated with either cyclophosphamide or temsirolimus and imaged with FLT-PET and FDG-PET on appropriate days post therapy inititiation. Immunohistochemical (IHC) studies (H&E, TUNEL, CD20, PCNA and ki-67) and DNA flow cytometry studies were performed.

Results

FDG tumor uptake decreased immediately after cyclophosphamide treatment while FLT-PET showed only a late and less pronounced decrease. A fast induction of apoptosis was observed together with an early accumulation of cells in the S-phase of the cell cycle, suggesting DNA repair. Temsirolimus treatment reduced both FDG and FLT tumor uptake immediately after therapy and resulted in a fast induction of apoptosis and G0-G1 phase accumulation.

Conclusion

FLT response was less distinct than FDG response and may be controlled by DNA repair early after cyclophosphamide. Nevertheless, FLT-PET was able to reflect decreased proliferation following temsirolimus.

Purpose

Positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG-PET) has increasingly been used to evaluate the efficacy of anticancer agents. We investigated the role of FDG-PET as a predictive marker for response to mammalian target of rapamycin (mTOR) inhibition in advanced solid tumor patients and in murine xenograft models.

Patients and Methods

Thirty-four rapamycin-treated patients with assessable baseline and treatment FDG-PET and computed tomography scans were analyzed from two clinical trials. Clinical response was evaluated according to Response Evaluation Criteria in Solid Tumors, and FDG-PET response was evaluated by quantitative changes and European Organisation for Research and Treatment of Cancer (EORTC) criteria. Six murine xenograft tumor models were treated with temsirolimus. Small animal FDG-PET scans were performed at baseline and during treatment. The tumors were analyzed for the expression of pAkt and GLUT1.

Results

Fifty percent of patients with increased FDG-PET uptake and 46% with decreased uptake had progressive disease (PD). No objective response was observed. By EORTC criteria, the sensitivity of progressive metabolic disease on FDG-PET in predicting PD was 19%. Preclinical studies demonstrated similar findings, and FDG-PET response correlated with pAkt activation and plasma membrane GLUT1 expression.

Conclusion

FDG-PET is not predictive of proliferative response to mTOR inhibitor therapy in both clinical and preclinical studies. Our findings suggest that mTOR inhibitors suppress the formation of mTORC2 complex, resulting in the inhibition of Akt and glycolysis independent of proliferation in a subset of tumors. Changes in FDG-PET may be a pharmacodynamic marker for Akt activation during mTOR inhibitor therapy. FDG-PET may be used to identify patients with persistent Akt activation following mTOR inhibitor therapy.

PURPOSE: We report on a novel preclinical pancreatic cancer research model that uses bioluminescence imaging (BLI)-guided irradiation of orthotopic xenograft tumors, sparing of surrounding normal tissues, and quantitative, noninvasive longitudinal assessment of treatment response. MATERIALS AND METHODS: Luciferase-expressing MiaPaCa-2 pancreatic carcinoma cells were orthotopically injected in nude mice. BLI was compared to pathologic tumor volume, and photon emission was assessed over time. BLI was correlated to positron emission tomography (PET)/computed tomography (CT) to estimate tumor dimensions. BLI and cone-beam CT (CBCT) were used to compare tumor centroid location and estimate setup error. BLI and CBCT fusion was performed to guide irradiation of tumors using the small animal radiation research platform (SARRP). DNA damage was assessed by γ-H2Ax staining. BLI was used to longitudinally monitor treatment response. RESULTS: Bioluminescence predicted tumor volume (R = 0.8984) and increased linearly as a function of time up to a 10-fold increase in tumor burden. BLI correlated with PET/CT and necropsy specimen in size (P < .05). Two-dimensional BLI centroid accuracy was 3.5 mm relative to CBCT. BLI-guided irradiated pancreatic tumors stained positively for γ-H2Ax, whereas surrounding normal tissues were spared. Longitudinal assessment of irradiated tumors with BLI revealed significant tumor growth delay of 20 days relative to controls. CONCLUSIONS: We have successfully applied the SARRP to a bioluminescent, orthotopic preclinical pancreas cancer model to noninvasively: 1) allow the identification of tumor burden before therapy, 2) facilitate image-guided focal radiation therapy, and 3) allow normalization of tumor burden and longitudinal assessment of treatment response.

Despite the use of radiation and chemotherapy, the prognosis for children with diffuse brainstem gliomas is extremely poor. There is a need for relevant brainstem tumor models that can be used to test new therapeutic agents and delivery systems in pre-clinical studies. We report the development of a brainstem-tumor model in rats and the application of bioluminescence imaging (BLI) for monitoring tumor growth and response to therapy as part of this model. Luciferase-modified human glioblastoma cells from five different tumor cell sources (either cell lines or serially-passaged xenografts) were implanted into the pontine tegmentum of athymic rats using an implantable guide-screw system. Tumor growth was monitored by BLI and tumor volume was calculated by three-dimensional measurements from serial histopathologic sections. To evaluate if this model would allow detection of therapeutic response, rats bearing brainstem U-87 MG or GS2 glioblastoma xenografts were treated with the DNA methylating agent temozolomide (TMZ). For each of the tumor cell sources tested, BLI monitoring revealed progressive tumor growth in all animals, and symptoms caused by tumor burden were evident 26–29 days after implantation of U-87 MG, U-251 MG, GBM6, and GBM14 cells, and 37–47 days after implantation of GS2 cells. Histopathologic analysis revealed tumor growth within the pons in all rats and BLI correlated quantitatively with tumor volume. Variable infiltration was evident among the different tumors, with GS2 tumor cells exhibiting the greatest degree of infiltration. TMZ treatment groups were included for experiments involving U-87 MG and GS2 cells, and in each case TMZ delayed tumor growth, as indicated by BLI monitoring, and significantly extended survival of animal subjects. Our results demonstrate the development of a brainstem tumor model in athymic rats, in which tumor growth and response to therapy can be accurately monitored by BLI. This model is well suited for pre-clinical testing of therapeutics that are being considered for treatment of patients with brainstem tumors.

Small animal imaging provides diverse methods for evaluating tumor growth and acute response to therapy. This study compared the utility of non-invasive optical and ultrasound imaging to monitor growth of three diverse human tumor xenografts (brain U87-luc-mCherry, mammary MCF7-luc-mCherry, and prostate PC3-luc) growing in nude mice. Bioluminescence imaging (BLI), fluorescence imaging (FLI), and Power Doppler ultrasound (PD US) were then applied to examine acute vascular disruption following administration of arsenic trioxide (ATO).

During initial tumor growth, strong correlations were found between manual caliper measured tumor volume and FLI intensity, BLI intensity following luciferin injection, and traditional B-mode US. Administration of ATO to established U87 tumors caused significant vascular shutdown within 2 hrs at all doses in the range 5 to 10 mg/kg in a dose dependant manner, as revealed by depressed bioluminescent light emission. At lower doses substantial recovery was seen within 4 hrs. At 8 mg/kg there was >85% reduction in tumor vascular perfusion, which remained depressed after 6 hrs, but showed some recovery after 24 hrs. Similar response was observed in MCF7 and PC3 tumors. Dynamic BLI and PD US each showed similar duration and percent reductions in tumor blood flow, but FLI showed no significant changes during the first 24 hrs.

The results provide further evidence for comparable utility of optical and ultrasound imaging for monitoring tumor growth, More specifically, they confirm the utility of BLI and ultrasound imaging as facile assays of the vascular disruption in solid tumors based on ATO as a model agent.

Introduction and Purpose. Monitoring solid tumor growth and metastasis in small animals is important for cancer research. Noninvasive techniques make longitudinal studies possible, require fewer animals, and have greater statistical power. Such techniques include FDG positron emission tomography (FDG-PET), magnetic resonance imaging (MRI), and optical imaging, comprising bioluminescence imaging (BLI) and fluorescence imaging (FLI). This study compared the performance and usability of these methods in the context of mouse tumor studies. Methods. B16 tumor-bearing mice (n = 4 for each study) were used to compare practicality, performance for small tumor detection and tumor burden measurement. Using RETAAD mice, which develop spontaneous melanomas, we examined the performance of MRI (n = 6 mice) and FDG-PET (n = 10 mice) for tumor identification. Results. Overall, BLI and FLI were the most practical techniques tested. Both BLI and FDG-PET identified small nonpalpable tumors, whereas MRI and FLI only detected macroscopic, clinically evident tumors. FDG-PET and MRI performed well in the identification of tumors in terms of specificity, sensitivity, and positive predictive value. Conclusion. Each of the four methods has different strengths that must be understood before selecting them for use.

Purpose

To evaluate by sequential 18F-FDG PET/CT imaging the therapeutic response to a novel monoclonal antibody targeting human EMMPRIN (extracellular matrix metalloproteinase inducer) in combination with gemcitabine in a pancreatic-tumor xenograft murine model.

Procedures

Four groups of SCID mice bearing orthotopic pancreatic tumor xenografts were injected with PBS, gemcitabine (120mg/kg BW), anti-EMMPRIN antibody (0.2mg), or combination, respectively twice weekly for 2 weeks, while 18F-FDG PET/CT imaging was performed weekly for 3 weeks. Changes in mean standardized uptake value (SUVmean) of 18F-FDG and volume of tumors were determined.

Results

The tumor SUVmean change in the group receiving combination therapy was significantly lower than those of the other groups. Tumor-volume changes of groups treated with anti-EMMPRIN monotherapy or combined therapy were significantly lower than that of the control group.

Conclusions

These data provide support for clinical studies of anti-EMMPRIN therapy with gemcitabine for pancreatic cancer treatment.

We compared 68Ga-DOTA-F(ab′)2-herceptin (DOTA is 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid [HER2 PET]) and 18F-FDG PET for imaging of tumor response to the heat shock protein 90 (Hsp90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17AAG).

Methods

Mice bearing BT474 breast tumor xenografts were scanned with 18F-FDG PET and HER2 PET before and after 17AAG treatment and then biweekly for up to 3 wk.

Results

Within 24 h after treatment, a significant decrease in HER2 was measured by HER2 PET, whereas 18F-FDG PET uptake, a measure of glycolysis, was unchanged. Marked growth inhibition occurred in treated tumors but became evident only by 11 d after treatment. Thus, Her2 downregulation occurs independently of changes in glycolysis after 17AAG therapy, and Her2 reduction more accurately predicts subsequent tumor growth inhibition.

Conclusion

HER2 PET is an earlier predictor of tumor response to 17AAG therapy than 18F-FDG PET.

Bioluminescence imaging (BLI) has emerged as a powerful new modality for studies of viral infection and therapy in small animal models. BLI technology captures the light emitted from different luciferase enzymes to detect sites of viral infection and quantify viral replication in the context of a living animal. In this review, we discuss the biochemical features of various luciferase enzymes and modifications to these enzymes that can greatly enhance their ability to image viral infection, host responses and the effects of therapy. We also describe BLI instrumentation and technical aspects of BLI needed to optimize imaging data. Examples of BLI for quantitative analysis of viral infection and in vivo monitoring of antiviral and antibacterial therapy are presented to highlight the potential for BLI to accelerate discovery of new antiviral agents and determine efficacy of antiviral compounds. Ongoing research to use multiple luciferase enzymes to image viral infection, host immune signaling pathways, and cell trafficking in the same animal will continue to advance BLI for longitudinal, real-time quantification and analyses of viral infection and pre-clinical testing of promising therapeutic agents.

Background

Bioluminescent imaging (BLI) is based on the detection of light emitted by living cells expressing a luciferase gene. Stable transfection of luciferase in cancer cells and their inoculation into permissive animals allows the noninvasive monitorization of tumor progression inside internal organs. We have applied this technology for the development of a murine model of colorectal cancer involving the liver, with the aim of improving the pre-clinical evaluation of new anticancer therapies.

Results

A murine colon cancer cell line stably transfected with the luciferase gene (MC38Luc1) retains tumorigenicity in immunocompetent C57BL/6 animals. Intrahepatic inoculation of MC38Luc1 causes progressive liver infiltration that can be monitored by BLI. Compared with ultrasonography (US), BLI is more sensitive, but accurate estimation of tumor mass is impaired in advanced stages. We applied BLI to evaluate the efficacy of an immunogene therapy approach based on the liver-specific expression of the proinflammatory cytokine interleukin-12 (IL-12). Individualized quantification of light emission was able to determine the extent and duration of antitumor responses and to predict long-term disease-free survival.

Conclusion

We show that BLI is a rapid, convenient and safe technique for the individual monitorization of tumor progression in the liver. Evaluation of experimental treatments with complex mechanisms of action such as immunotherapy is possible using this technology.

Object

To evaluate the feasibility of positron emission tomography/magnetic resonance imaging (PET/MR) with 18fluoro-2-deoxyglucose (FDG) for therapy response evaluation of malignant lymphoma.

Materials and methods

Nine patients with malignant lymphoma who underwent FDG-PET/MR before and after chemotherapy were included in this retrospective study. Average time between the two scans was 70 days. The scans were evaluated independently by two nuclear medicine physicians. The Ann Arbor classification was used to describe lymphoma stage. Furthermore, the readers also rated PET image quality using a five point scale. Weighted kappa (κ) was used to calculate interrater agreement.

Results

The initial scan showed foci of increased FDG uptake in all patients, with Ann Arbor stage varying between I and IV. In the follow-up examination, all but one patient showed complete response to chemotherapy. PET image quality was rated as very good or excellent for all scans. Interrater agreement was excellent regarding Ann Arbor stage (κ = 0.97) and good regarding image quality (κ = 0.41).

Conclusion

PET/MR shows promising initial results for therapy response evaluation in lymphoma patients.

Purpose

To determine whether treatment response to the Aurora B kinase inhibitor, AZD1152, could be monitored early in the course of therapy by non-invasive [18F]FDG and/or [18F]FLT PET imaging.

Experimental design

AZD1152-treated and control HCT116 and SW620 xenograft-bearing animals were monitored for tumor size and by [18F]FDG and [18F]FLT PET imaging. Additional studies assessed the endogenous and exogenous contributions thymidine synthesis in the two cell lines.

Results

Both xenografts showed a significant volume-reduction to AZD1152. In contrast, [18F]FDG uptake did not demonstrate a treatment response. [18F]FLT uptake decreased to less than 20% of control values in AZD1152-treated HCT116 xenografts, whereas [18F]FLT uptake was near background levels in both treated and untreated SW620 xenografts. The EC50 for AZD1152-HQPA was ~10 nM in both SW620 and HCT116 cells; in contrast, SW620 cells were much more sensitive to Methotrexate (MTX) and 5-Fluorouracil (5FU) than HCT116 cells. Immunoblot analysis demonstrated marginally lower expression of thymidine kinase in SW620 compared to HCT116 cells. The above results suggest that SW620 xenografts have a higher dependency on the de novo pathway of thymidine utilization than HCT116 xenografts.

Conclusions

AZD1152 treatment showed anti-tumor efficacy in both colon cancer xenografts. Although [18F]FDG PET was inadequate in monitoring treatment-response, [18F]FLT PET was very effective in monitoring response in HCT116 xenografts, but not in SW620 xenografts. These observations suggest that de novo thymidine synthesis could be a limitation and confounding factor for [18F]FLT PET imaging and quantification of tumor proliferation, and this may apply to some clinical studies as well.

Recent developments have established molecular imaging of mouse models with small-animal PET and bioluminescence imaging (BLI) as an important tool in cancer research. One of the disadvantages of these imaging modalities is the lack of anatomic information. We combined small-animal PET and BLI technology with small-animal CT to obtain fusion images with both molecular and anatomic information.

Methods

We used small-animal PET/CT and BLI to detect xenografts of different cell lines and metastases of a melanoma cell line (A375M-3F) that had been transduced with a lentiviral vector containing a trimodality imaging reporter gene encoding a fusion protein with Renilla luciferase, monomeric red fluorescent protein, and a mutant herpes simplex virus type 1 thymidine kinase.

Results

Validation studies in mouse xenograft models showed a good coregistration of images from both PET and CT. Melanoma metastases were detected by 18F-FDG PET, 9-[4-18F-fluoro-3-(hydroxymethyl) butyl]guanine (18F-FHBG) PET, CT, and BLI and confirmed by ex vivo assays of Renilla luciferase and mutant thymidine kinase expression. 18F-FHBG PET/CT allowed detection and localization of lesions that were not seen on CT because of poor contrast resolution and were not seen on 18F-FDG PET because of higher background uptake relative to 18F-FHBG.

Conclusion

The combination of 18F-FHBG PET, small-animal CT, and BLI allows a sensitive and improved quantification of tumor burden in mice. This technique is potentially useful for the study of the biologic determinants of metastasis and for the evaluation of novel cancer treatments.

A 53-year-old man with a diagnosis of gastric non-Hodgkin lymphoma (NHL) underwent PET/CT scans both prior to starting chemotherapy and immediately following completion of chemotherapy to evaluate the response to therapy. Pre-therapy PET/CT images showed intense FDG uptake in the antral region of the stomach. Biodistribution of FDG was otherwise unremarkable. The patient was started on metformin in the middle of his therapy period to provide glycemic control. Post-therapy PET/CT study performed after 6 courses of chemotherapy showed complete resolution of the disease with no evidence of residual FDG uptake. However, intense and diffuse FDG accumulation is observed in the bowel, which was interpreted as physiological and most probably due to metformin administration. It should be borne in mind that there are a number of physiological variants of FDG biodistribution seen on PET/CT imaging. Recognizing physiologic bowel activity is crucial for the accuracy of PET image interpretation.

Conflict of interest:None declared.

Objectives: Most chemotherapy agents cause tumor cell death primarily by the induction of apoptosis. The ability to noninvasively image apoptosis in vivo could dramatically benefit pre-clinical and clinical evaluation of chemotherapeutics targeting the apoptotic pathway. This study aims to visualize the dynamics of apoptotic process with temporal bioluminescence imaging (BLI) using an apoptosis specific bioluminescence reporter gene. Methods: Both UM-SCC-22B human head and neck squamous carcinoma cells and 4T1 murine breast cancer cells were genetically modified with a caspase-3 specific cyclic firefly luciferase reporter gene (pcFluc-DEVD). Apoptosis induced by different concentrations of doxorubicin in the transfected cells was evaluated by both annexin V staining and BLI. Longitudinal BLI was performed in xenografted tumor models at different time points after doxorubicin or Doxil treatment, to evaluate apoptosis. After imaging, DNA fragmentation in apoptotic cells was assessed in frozen tumor sections using TUNEL staining. Results: Dose- and time-dependent apoptosis induced by doxorubicin in pcFluc-DEVD transfected UM-SCC-22B and 4T1 cells was visualized and quantified by BLI. Caspase-3 activation was confirmed by both caspase activity assay and GloTM luciferase assay. One dose of doxorubicin treatment induced a dramatic increase in BLI intensity as early as 24 h after treatment in 22B-pcFluc-DEVD xenografted tumors. Sustained signal increase was observed for the first 3 days and the fluorescent signal from ex vivo TUNEL staining was consistent with BLI imaging results. Long-term imaging revealed that BLI signal consistently increased and reached a maximum at around day 12 after the treatment with one dose of Doxil. Conclusions: BLI of apoptosis with pcFluc-DEVD as a reporter gene facilitates the determination of kinetics of the apoptotic process in a real-time manner, which provides a unique tool for drug development and therapy response monitoring.

Abstract

Current assessment of orthotopic tumor models in animals utilizes survival as the primary therapeutic end point. In vivo bioluminescence imaging (BLI) is a sensitive imaging modality that is rapid and accessible, and may comprise an ideal tool for evaluating anti-neoplastic therapies [1]. Using human tumor cell lines constitutively expressing luciferase, the kinetics of tumor growth and response to therapy have been assessed in intraperitoneal [2], subcutaneous, and intravascular [3] cancer models. However, use of this approach for evaluating orthotopic tumor models has not been demonstrated. In this report, the ability of BLI to noninvasively quantitate the growth and therapeutic-induced cell kill of orthotopic rat brain tumors derived from 9L gliosarcoma cells genetically engineered to stably express firefly luciferase (9LLuc) was investigated. Intracerebral tumor burden was monitored over time by quantitation of photon emission and tumor volume using a cryogenically cooled CCD camera and magnetic resonance imaging (MRI), respectively. There was excellent correlation (r=0.91) between detected photons and tumor volume. A quantitative comparison of tumor cell kill determined from serial MRI volume measurements and BLI photon counts following 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) treatment revealed that both imaging modalities yielded statistically similar cell kill values (P=.951). These results provide direct validation of BLI imaging as a powerful and quantitative tool for the assessment of antineoplastic therapies in living animals.

Positron emission tomography (PET) imaging has become a useful tool for assessing early biologic response to cancer therapy and may be particularly useful in the development of new cancer therapeutics. RAF265, a novel B-Raf/vascular endothelial growth factor receptor-2 inhibitor, was evaluated in the preclinical setting for its ability to inhibit the uptake of PET tracers in the A375M(B-RafV600E) human melanoma cell line. RAF265 inhibited 2-deoxy-2-[18F]fluoro-d-glucose (FDG) accumulation in cell culture at 28 hours in a dose-dependent manner. RAF265 also inhibited FDG accumulation in tumor xenografts after 1 day of drug treatment. This decrease persisted for the remaining 2 weeks of treatment. DNA microarray analysis of treated tumor xenografts revealed significantly decreased expression of genes regulating glucose and thymidine metabolism and revealed changes in apoptotic genes, suggesting that the imaging tracers FDG, 3-deoxy-3-[18F]fluorothymidine, and annexin V could serve as potential imaging biomarkers for RAF265 therapy monitoring. We concluded that RAF265 is highly efficacious in this xenograft model of human melanoma and decreases glucose metabolism as measured by DNA microarray analysis, cell culture assays, and small animal FDG PET scans as early as 1 day after treatment. Our results support the use of FDG PET in clinical trials with RAF265 to assess early tumor response. DNA microarray analysis and small animal PET studies may be used as complementary technologies in drug development. DNA microarray analysis allows for analysis of drug effects on multiple pathways linked to cancer and can suggest corresponding imaging tracers for further analysis as biomarkers of tumor response.

Multiple myeloma (MM) is an incurable B-cell neoplasia in which progressive skeletal lesions are a characteristic feature. Earlier we established an animal model for human MM in the immune-deficient RAG2-/-γc-/- mouse, in which the growth of luciferase-transduced MM cells was visualized using noninvasive bioluminescence imaging (BLI). This model appeared well suited to study disease progression and response to therapy by identifying the location of various foci of MM tumor growth scattered throughout the skeleton and at subsequent time points the quantitative assessment of the tumor load by using BLI. We report here on the corresponding high-resolution X-ray micro-computed tomographic (micro-CT) analysis to study skeletal defects in the mice with full-blown MM. Several anatomical derangements were observed, including abnormalities in geometry and morphology, asymmetrical bone structures, decreased overall density in the remaining bone, loss of trabecular bone mass, destruction of the inner microarchitecture, as well as cortical perforations. Using the combination of BLI, micro-CT imaging, and immune-histopathological techniques, we found a high correlation between the micro-CT-identified lesions, exact tumor location, and infiltration leading to structural lesions and local bone deformation. This confirms that this animal model strongly resembles human MM and has the potential for studying the biology of MM growth and for preclinical testing of novel therapies for MM and for repair of MM-induced bone lesions.

Purpose. The aim of this study was to prospectively evaluate whether FDG-PET allows an accurate assessment of histopathologic response to neoadjuvant treatment in adult patients with primary bone sarcomas. Methods. Twelve consecutive patients with resectable, primary high grade bone sarcomas were enrolled prospectively. FDG-PET/CT imaging was performed prior to the initiation and after completion of neoadjuvant treatment. Imaging findings were correlated with histopathologic response. Results. Histopathologic responders showed significantly more pronounced decreases in tumor FDG-SUVmax from baseline to late follow up than non-responders (64 ± 19% versus 29 ± 30 %, resp.; P = .03). Using a 60% decrease in tumor FDG-uptake as a threshold for metabolic response correctly classified 3 of 4 histopathologic responders and 7 of 8 histopathologic non-responders as metabolic responders and non-responders, respectively (sensitivity, 75%; specificity, 88%). Conclusion. These results suggest that changes in FDG-SUVmax at the end of neoadjuvant treatment can identify histopathologic responders and non-responders in adult primary bone sarcoma patients.

Testicular relapse of leukemia and lymphoma is a well-recognized phenomenon, with testicular relapse of lymphoma being more common in the adult population and leukemia relapse being more common in the pediatric population. With the advent of F-18 fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in the evaluation of lymphoma it is possible to evaluate testicular uptake of FDG and to detect primary testicular lymphoma or testicular relapse on the FDG-PET examination. Testicular relapse of non-Hodgkin lymphoma (NHL) detected on FDG-PET has been reported previously. We report an additional case in which there was testicular activity at presentation, a response to therapy (orchiectomy not performed) and then testicular relapse followed by orchiectomy. We review the literature with regard to testicular recurrence and testicular uptake of FDG-PET. There have been studies that have examined normal standardized uptake value maximum (SUVmax) values in the testicle, with normal values ranging from 2.81 (30–39 years) to 2.18 (80–89 years), depending upon age. However, it should be noted that there could be considerable variability in SUVmax values depending upon the units used (e.g. normalized to lean body mass vs. body weight) and depending upon examination variables such as dietary conditions, muscle uptake or extravasation of FDG. Elevated activity or lateralizing activity should be viewed with suspicion, with etiologies including primary testicular tumor, primary or secondary testicular lymphoma and metastatic disease with other etiologies less likely.

KITENIN (KAI1 C-terminal interacting tetraspanin) promotes invasion and metastasis in mouse colon cancer models. In the present study, we evaluated the effects of KITENIN knockdown by intravenous administration of short hairpin RNAs (shRNAs) in an orthotopic mouse colon cancer model, simulating a primary or adjuvant treatment setting. We established orthotopic models for colon cancer using BALB/c mice and firefly luciferase-expressing CT-26 (CT26/Fluc) cells. Tumor progression and response to therapy were monitored by bioluminescence imaging (BLI). In the primary therapy model, treatment with KITENIN shRNA substantially delayed tumor growth (P = 0.028) and reduced the incidence of hepatic metastasis (P = 0.046). In the adjuvant therapy model, KITENIN shRNA significantly reduced the extent of tumor recurrence (P = 0.044). Mice treated with KITENIN shRNA showed a better survival tendency than the control mice (P = 0.074). Our results suggest that shRNA targeting KITENIN has the potential to be an effective tool for the treatment of colon cancer in both adjuvant and metastatic setting.

Purpose

Response to neo-adjuvant chemotherapy is an important prognostic factor for osteosarcoma (OS) and the Ewing sarcoma family of tumors (ESFT). [F-18]-fluorodeoxy-D-glucose (FDG)-positron emission tomography (PET) is a non-invasive imaging modality that predicts histologic response to chemotherapy of various malignancies; however, limited data exist about the usefulness of FDG-PET in predicting the histologic response of pediatric bone tumors to chemotherapy. We analyzed the FDG-PET imaging characteristics of pediatric bone tumors and determined the association with response to chemotherapy.

Materials and Methods

Pediatric patients with OS (n=19) or ESFT (n=17) were evaluated for FDG-PET standard uptake values before (SUV1) and after (SUV2) chemotherapy. The relationship to the chemotherapy response was assessed by histopathology in surgically-excised tumors. A complete data set (SUV1, SUV2, and histologic response) was available in 23 patients.

Results

While the mean SUV1s were not different between patients with OSs and ESFTs (9.44 vs. 6.07, p=0.24), the SUV2s were greater in the patients with OSs than ESFTs (4.55 vs. 1.66, p=0.01). The ratios of SUV2-to-SUV1 (SUV2 : SUV1) were 0.65 and 0.35 for OS and ESFT, respectively (p=0.08). All of the patients with ESFTs and 47% of the patients with OS had a favorable histologic response to chemotherapy. The SUV2 : 1 [(SUV1-SUV2)/SUV1]≥0.5 and SUV2≤2.5 were related to favorable histologic responses to chemotherapy; the sensitivity and specificity of SUV2 : 1 at 0.5 and SUV2 at 2.5 were 93% and 88%, and 88% and 78%, respectively.

Conclusion

FDG-PET can be used as a non-invasive surrogate to predict response to chemotherapy in children with bone tumors.

Purpose of the study

Fever of unknown origin (FUO) is a challenging clinical entity in HIV patients. FDG-PET/CT is well validated in the work-up of FUO in HIV-negative patients but in HIV viremic patients, metabolism of HIV reactive lymph nodes could decrease its specificity. We prospectively evaluated the usefulness of FDG-PET/CT in FUO in HIV-positive patients and in particular whether HIV viremia impacts on FDG-PET/CT performance.

Methods

FDG-PET/CT was performed in 20 HIV patients with FUO and compared with FDG-PET/CT in 10 HIV viremic patients without FUO. Final diagnosis for FUO was based on histopathology, microbiology, or clinical and imaging follow-up. Mode of diagnosis, accordance of FDG-PET/CT with final diagnosis, localization of invasive diagnosis procedures was recorded in order to assess usefulness of FDG-PET/CT.

Results

FDG-PET/CT showed a different pattern in FUO and asymptomatic viremic patients. Reactive HIV lymph nodes in asymptomatic viremic patients were mostly peripheral with mean SUVmax of 6.5. In patients with FUO and underlying focal pathologies, hypermetabolic lymph nodes were central with mean SUVmax of 11.6. Presence of central lymph nodes with high FDG uptake in had a 100% specificity for focal pathology, even in viremic patients and absence of these had 100% negative predictive value. Lymph node biopsy in central hypermetabolic areas allowed identifying underlying disease in all FUO patients. For peripheral lymph nodes, a ROC curve was built in order to define the best cut-off of SUVmax for biopsy: SUVmax of 6–8 showed a sensitivity of 62.5% and specificity of 75%. Lymph nodes with SUVmax<4 had sensitivity of 0%.

Conclusions

FDG-PET/CT contributed to the diagnosis or exclusion of a focal etiology of the febrile state in 80% of HIV patients with FUO. Although number of patients was small, we could highlight several clear-cut features to help interpreting FDG-PET/CT in HIV patients with FUO. As in HIV-negative patients, we showed the usefulness of FDG-PET/CT in FUO in HIV patients even if they are viremic.

Abstract

This study investigates the relationship between FDG uptake as determined by positron emission tomography (PET) imaging and rates of tumor growth, cellular GLUT1 transporter density, and the activities of hexokinase and glucose-6-phosphatase in a solid tumor implant model. Five different human colorectal xenografts of different growth properties were implanted in athymic rats and evaluated by dynamic 18F-FDG-PET. The phosphorylating and dephosphorylating activities of the key glycolytic enzymes, hexokinase and glucose-6-phosphatase, were measured in these tumor types by spectrophotometric assays and the expression of GLUT1 glucose transporter protein was determined by immunohistochemistry. Correlations among FDG accumulation, hexokinase activity, and tumor doubling time are reported in these colon xenografts. The results indicate that the activity of tumor hexokinase may be a marker of tumor growth rate that can be determined by 18F-FDG-PET imaging. PET scanning may not only be a useful tool for staging patients for extent of disease, but may provide important prognostic information concerning the proliferative rates of malignancies.

Purpose of the Report

This study tested the feasibility of C11-acetate (acetate) positron emission tomography (PET) imaging to assess response to therapy in men with bone metastatic prostate cancer and compared results for disease detection and response evaluation with F-18 fluorodeoxyglucose (FDG) PET.

Materials and Methods

Men with ≥3 prostate cancer bone metastases identified by Tc-99m methylene diphosphonate (MDP) bone scintigraphy and/or computed tomography were enrolled in a prospective study of serial acetate and FDG PET imaging. Patients were imaged before and 6 to 12 weeks after initial androgen deprivation therapy for new metastatic prostate cancer or first-line chemotherapy with docetaxel for castration-resistant prostate cancer. Qualitative assessment and changes in the tumor:normal uptake ratio were used to assess response by both acetate and FDG PET. In addition, the detection of bone metastases pretherapy was compared for acetate and FDG PET.

Results

A total of 8 patients with documented bone metastases were imaged, of which 6 were imaged both pre- and post-therapy. Acetate PET detected bone metastases in all 8 patients, whereas FDG PET detected lesions in 6 of the 7 imaged patients. Acetate PET generally detected more metastases with a higher tumor:normal uptake ratio. Qualitative and quantitative assessments of post-treatment response correlated with composite clinical designations of response, stable disease, or progression in 6 of 6 and 5 of 6 by acetate and 4 of 5 and 3 of 5 by FDG PET, respectively.

Conclusions

In this pilot study, results indicate that acetate PET holds promise for response assessment of prostate cancer bone metastases and is complementary to FDG PET in bone metastasis detection.