Functional imaging of localized prostate cancer aggressiveness using 11C-acetate PET/CT and 1H-MR spectroscopy

Multi-Modality Imaging of Atheromatous Plaques in Peripheral Arterial Disease: Integrating Molecular and Imaging Markers

Peripheral artery disease (PAD) is a common and debilitating condition characterized by the narrowing of the limb arteries, primarily due to atherosclerosis. Non-invasive multi-modality imaging approaches using computed tomography (CT), magnetic resonance imaging (MRI), and nuclear imaging have emerged as valuable tools for assessing PAD atheromatous plaques and vessel walls. This review provides an overview of these different imaging techniques, their advantages, limitations, and recent advancements. In addition, this review highlights the importance of molecular markers, including those related to inflammation, endothelial dysfunction, and oxidative stress, in PAD pathophysiology. The potential of integrating molecular and imaging markers for an improved understanding of PAD is also discussed. Despite the promise of this integrative approach, there remain several challenges, including technical limitations in imaging modalities and the need for novel molecular marker discovery and validation. Addressing these challenges and embracing future directions in the field will be essential for maximizing the potential of molecular and imaging markers for improving PAD patient outcomes.

Molecular Imaging in Primary Staging of Prostate Cancer Patients: Current Aspects and Future Trends

Accurate primary staging is the cornerstone in all malignancies. Different morphological imaging modalities are employed in the evaluation of prostate cancer (PCa). Regardless of all developments in imaging, invasive histopathologic evaluation is still the standard method for the detection and staging of the primary PCa. Magnetic resonance imaging (MRI) and computed tomography (CT) play crucial roles; however, functional imaging provides additional valuable information, and it is gaining ever-growing acceptance in the management of PCa. Targeted imaging with different radiotracers has remarkably evolved in the past two decades. [111In]In-capromab pendetide scintigraphy was a new approach in the management of PCa. Afterwards, positron emission tomography (PET) tracers such as [11C/18F]choline and [11C]acetate were developed. Nevertheless, none found a role in the primary staging. By introduction of the highly sensitive small molecule prostate-specific membrane antigen (PSMA) PET/CT, as well as recent developments in MRI and hybrid PET/MRI systems, non-invasive staging of PCa is being contemplated. Several studies investigated the role of these sophisticated modalities in the primary staging of PCa, showing promising results. Here, we recapitulate the role of targeted functional imaging. We briefly mention the most popular radiotracers, their diagnostic accuracy in the primary staging of PCa, and impact on patient management.

Correlation between 18F-1-amino-3-fluorocyclobutane-1-carboxylic acid (18F-fluciclovine) uptake and expression of alanine-serine-cysteine-transporter 2 (ASCT2) and L-type amino acid transporter 1 (LAT1) in primary prostate cancer

Purpose

To evaluate the expression of alanine-serine-cysteine-transporter 2 (ASCT2) and L-type amino acid transporter1 (LAT1) in prostate cancer (PCa) and their impact on uptake of ¹⁸F-1-amino-3-fluorocyclobutane-1-carboxylic acid (¹⁸F-fluciclovine) which is approved for the detection of recurrent PCa.

Methods

Twenty-five hormone-naïve patients with histologically confirmed PCa underwent PET/CT before prostatectomy. Dynamic imaging was performed immediately after injection of 368 ± 10 MBq of ¹⁸F-fluciclovine and the uptake in PCa was expressed as SUV_max at six sequential 4-min time frames and as tracer distribution volume (V_T) using Logan plots over 0–24 min. The expression of ASCT2 and LAT1 was studied with immunohistochemistry (IHC) on a tissue microarray (TMA) containing three cores per carcinoma lesion. The TMA slides were scored independently by two trained readers based on visual intensity of ASCT2/LAT1 expression on a four-tiered scale. The correlations between ASCT2/LAT1 staining intensity, SUVmax/V_T, and Gleason grade group (GGG) were assessed using Spearman’s rank correlation coefficient (ρ).

Results

Forty tumor foci (> 0.5 mm in diameter, max. 3 per patient) were available for TMA. In visual scoring, low, moderate, and high staining intensity of ASCT2 was observed in 4 (10%), 24 (60%), and 12 (30%) tumors, respectively. No tumors showed high LAT1 staining intensity while moderate intensity was found in 10 (25%), 25 (63%) showed low, and the remaining 5 (12%) were negative for staining with LAT1. Tumors with GGG > 2 showed significantly higher uptake of ¹⁸F-fluciclovine and higher LAT1 staining intensity (p < 0.05). The uptake of ¹⁸F-fluciclovine correlated significantly with LAT1 expression (ρ = 0.39, p = 0.01, for SUV_max at 2 min and ρ = 0.39, p = 0.01 for V_T). No correlation between ASCT2 expression and ¹⁸F-fluciclovine uptake or GGG was found.

Conclusions

Our findings suggest that LAT1 is moderately associated with the transport of ¹⁸F-fluciclovine in local PCa not exposed to hormonal therapy. Both high and low Gleason grade tumors express ASCT2 while LAT1 expression is less conspicuous and may be absent in some low-grade tumors. Our observations may be of importance when using ¹⁸F-fluciclovine imaging in the planning of focal therapies for PCa.

Positron emission tomography in prostate cancer: An update on state of the art

Prostate cancer (PCa), one of the most common cancers in males, is a topic of active interest in imaging research. Positron emission tomography/computed tomography (PET/CT) and PET/magnetic resonance imaging (PET/MRI) have enabled the combination of morphologic and functional imaging with the promise of providing better information in guiding therapy. ¹⁸F-fluorodeoxyglucose, the workhorse radiopharmaceutical in PET imaging, has not found preference in PCa since these tumors show poor glucose uptake and can be obscured by the normal urinary excretion of the radiotracer. Hence, the last two decades have seen the development of multiple newer radiotracers and better optimization of the technical aspects of PET imaging. The combination of functional imaging and MRI holds great promise. We searched PubMed, Scopus, and Google Scholar for peer-reviewed literature concerning the advances and newer developments in the imaging of PCa between the years 2005 and 2017. This review aims at summarizing current evidence on the role of PET imaging in PCa and its impact on the diagnosis, staging, prognostication, response assessment, and restaging of this malignancy.

Prospective evaluation of 18F-FACBC PET/CT and PET/MRI versus multiparametric MRI in intermediate- to high-risk prostate cancer patients (FLUCIPRO trial)

PURPOSE

The purpose of this study was to evaluate ¹⁸F-FACBC PET/CT, PET/MRI, and multiparametric MRI (mpMRI) in detection of primary prostate cancer (PCa).

METHODS

Twenty-six men with histologically confirmed PCa underwent PET/CT immediately after injection of 369 ± 10 MBq ¹⁸F-FACBC (fluciclovine) followed by PET/MRI started 55 ± 7 min from injection. Maximum standardized uptake values (SUV_max) were measured for both hybrid PET acquisitions. A separate mpMRI was acquired within a week of the PET scans. Logan plots were used to calculate volume of distribution (V_T). The presence of PCa was estimated in 12 regions with radical prostatectomy findings as ground truth. For each imaging modality, area under the curve (AUC) for detection of PCa was determined to predict diagnostic performance. The clinical trial registration number is NCT02002455.

RESULTS

In the visual analysis, 164/312 (53%) regions contained PCa, and 41 tumor foci were identified. PET/CT demonstrated the highest sensitivity at 87% while its specificity was low at 56%. The AUC of both PET/MRI and mpMRI significantly (p < 0.01) outperformed that of PET/CT while no differences were detected between PET/MRI and mpMRI. SUV_max and V_T of Gleason score (GS) >3 + 4 tumors were significantly (p < 0.05) higher than those for GS 3 + 3 and benign hyperplasia. A total of 442 lymph nodes were evaluable for staging, and PET/CT and PET/MRI demonstrated true-positive findings in only 1/7 patients with metastatic lymph nodes.

CONCLUSIONS

Quantitative ¹⁸F-FACBC imaging significantly correlated with GS but failed to outperform MRI in lesion detection. ¹⁸F-FACBC may assist in targeted biopsies in the setting of hybrid imaging with MRI.

Molecular imaging probes derived from natural peptides

Covering: up to the end of 2015.Peptides are naturally occurring compounds that play an important role in all living systems and are responsible for a range of essential functions. Peptide receptors have been implicated in disease states such as oncology, metabolic disorders and cardiovascular disease. Therefore, natural peptides have been exploited as diagnostic and therapeutic agents due to the unique target specificity for their endogenous receptors. This review discusses a variety of natural peptides highlighting their discovery, endogenous receptors, as well as their derivatization to create molecular imaging agents, with an emphasis on the design of radiolabelled peptides. This review also highlights methods for discovering new and novel peptides when knowledge of specific targets and endogenous ligands are not available.

Evaluation of Prostate Cancer with 11C-Acetate PET/CT

In this article, we will first describe the metabolic fate of ¹¹C-acetate; then discuss its biodistribution in health and disease; and subsequently focus on its key clinical applications, the detection and localization of prostate cancer tissue in patients with primary or recurrent disease. Finally, we will discuss the potential role of ¹¹C-acetate in the context of other prostate cancer imaging probes and non-radionuclide-based imaging approaches.

PET Tracers Beyond FDG in Prostate Cancer

Conventional anatomical imaging with CT and MRI has limitations in the evaluation of prostate cancer. PET is a powerful imaging technique, which can be directed toward molecular targets as diverse as glucose metabolism, density of prostate-specific membrane antigen receptors, and skeletal osteoblastic activity. Although 2-deoxy-2-18F-FDG-PET is the mainstay of molecular imaging, FDG has limitations in typically indolent prostate cancer. Yet, there are many useful and emerging PET tracers beyond FDG, which provide added value. These include radiotracers interrogating prostate cancer via molecular mechanisms related to the biology of choline, acetate, amino acids, bombesin, and dihydrotestosterone, among others. Choline is used for cell membrane synthesis and its metabolism is upregulated in prostate cancer. 11C-choline and 18F-choline are in wide clinical use outside the United States, and they have proven most beneficial for detection of recurrent prostate cancer. 11C-acetate is an indirect biomarker of fatty acid synthesis, which is also upregulated in prostate cancer. Imaging of prostate cancer with 11C-acetate is overall similar to the choline radiotracers yet is not as widely used. Upregulation of amino acid transport in prostate cancer provides the biologic basis for amino acid-based radiotracers. Most recent progress has been made with the nonnatural alicyclic amino acid analogue radiotracer anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid (FACBC or fluciclovine) also proven most useful for the detection of recurrent prostate cancer. Other emerging PET radiotracers for prostate cancer include the bombesin group directed to the gastrin-releasing peptide receptor, 16β-18F-fluoro-5α-dihydrotestosterone (FDHT) that binds to the androgen receptor, and those targeting the vasoactive intestinal polypeptide receptor 1 (VPAC-1) and urokinase plasminogen activator receptor (uPAR), which are also overexpressed in prostate cancer.

Evaluation of fatty acid synthase in prostate cancer recurrence: SUV of [(11) C]acetate PET as a prognostic marker

AIM

High levels of fatty acid synthase have shown to correlate with the aggressiveness of prostate cancer. As [(11) C]acetate exhibits a close correlation with the level of fatty acid synthase, we aimed to assess whether the SUV in [(11) C]acetate PET serves as a suitable prognostic marker in patients with recurrent prostate cancer.

MATERIALS AND METHODS

In 123 consecutive patients, examined between 2010 and 2014, the maximum standardized uptake value (SUVmax) of local recurrences as well as lymph node and bone metastases was measured. Choosing the spleen as a standard for relatively high physiological uptake, a ratio of tumor to spleen uptake (SUVts) was calculated for standardizing the uptake, too. The corresponding initial Gleason scores (GS) and serum-PSA levels around the time of the performed PET/CT for each patient were retrospectively collected and PSA doubling together with PSA velocity were determined. For further analysis patients were divided with regard to their initial Gleason score (≤3 + 4 and ≥ 4 + 3). The median of PSA velocity was calculated to separate patients with a high and low PSA velocity and Mann-Whitney U or Student's t-test were used, testing for significant differences. For correlation Spearmen-Rho test was used.

RESULTS

PET was positive for recurrence in 82/123 patients. PSA was significantly higher in PET-positive than in negative patients (5.9 vs. 3.2 ng/ml; P = 0.006). Initial Gleason score did not differ in PET negative and positive patients (P = 0.3), whereas PSA velocity was markedly higher in PET positive patients (0.4 vs. 0.1 ng/ml/month; P = 0.01). Median SUVmax of PET positive patients was 5.23 (mean 5.78; range 0.9-16.8) and meadian SUVts was 0.78 (mean 0.84, range 0.14-2.50). SUVts was significantly higher in patients with high PSA velocity (SUVts 0.76 vs. 0.92; P = 0.009), whereas SUVmax failed statistical significance (5.4 vs. 6.3 ng/ml/month; P = 0.08). Patients with a high SUVmax proved to have a significantly higher median Gleason score compared to low uptake 8.0 vs. 7.0; P = 0.004). Vice versa both SUVmax (GS 6: 5.0; GS 7: 5.6; GS 8: 5.7; GS 9: 6.5; r = 0.30, P = 0.008) and SUVts (GS 6: 0.63; GS 7: 0.68; GS 8: 0.85; GS 9: 0.89; r = 0.30, P = 0.006) significantly correlated with Gleason score. Patients with a Gleason score ≤ 3 + 4 had a significantly lower SUVmax (4.8 vs. 5.7; P = 0.02) and SUVts (0.67 vs. 0.85; P = 0.02) as compared to a Gleason score ≥ 4 + 3.

CONCLUSION

[(11) C]acetate uptake demonstrated to correlate with initial Gleason score. Furthermore, patients with a high PSA velocity proved to have higher [(11) C]acetate uptake in tumor lesions.

Current Status of Hybrid PET/MRI in Oncologic Imaging

OBJECTIVE

This review article explores recent advancements in PET/MRI for clinical oncologic imaging.

CONCLUSION

Radiologists should understand the technical considerations that have made PET/MRI feasible within clinical workflows, the role of PET tracers for imaging various molecular targets in oncology, and advantages of hybrid PET/MRI compared with PET/CT. To facilitate this understanding, we discuss clinical examples (including gliomas, breast cancer, bone metastases, prostate cancer, bladder cancer, gynecologic malignancy, and lymphoma) as well as future directions, challenges, and areas for continued technical optimization for PET/MRI.

Comparison of meta-analyses among elastosonography (ES) and positron emission tomography/computed tomography (PET/CT) imaging techniques in the application of prostate cancer diagnosis

The early diagnosis of prostate cancer (PCa) appears to be of vital significance for the provision of appropriate treatment programs. Even though several sophisticated imaging techniques such as positron emission tomography/computed tomography (PET/CT) and elastosonography (ES) have already been developed for PCa diagnosis, the diagnostic accuracy of these imaging techniques is still controversial to some extent. Therefore, a comprehensive meta-analysis in this study was performed to compare the accuracy of various diagnostic imaging methods for PCa, including 11C-choline PET/CT, 11C-acetate PET/CT, 18F-fluorocholine PET/CT, 18F-fluoroglucose PET/CT, transrectal real-time elastosonography (TRTE), and shear-wave elastosonography (SWE). The eligible studies were identified through systematical searching for the literature in electronic databases including PubMed, Cochrane, and Web of Science. On the basis of the fixed-effects model, the pooled sensitivity (SEN), specificity (SPE), and area under the receiver operating characteristics curve (AUC) were calculated to estimate the diagnostic accuracy of 11C-choline PET/CT, 11C-acetate PET/CT, 18F-fluorocholine (FCH) PET/CT, 18F-fluoroglucose (FDG) PET/CT, TRTE, and SWE. All the statistical analyses were conducted with R language Software. The present meta-analysis incorporating a total of 82 studies demonstrated that the pooled sensitivity of the six imaging techniques were sorted as follows: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 11C-acetate PET/CT > 18F-FDG PET/CT; the pooled specificity were also compared: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 18F-FDG PET/CT > 11C-acetate PET/CT; finally, the pooled diagnostic accuracy of the six imaging techniques based on AUC were ranked as below: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 11C-acetate PET/CT > 18F-FDG PET/CT. SWE and 18F-FCH PET/CT imaging could offer more assistance in the early diagnosis of PCa than any other studied imaging techniques. However, the diagnostic ranking of the six imaging techniques might not be applicable to the clinical phase due to the shortage of stratified analysis.

A prospective study of the efficacy of magnetic resonance spectroscopy imaging for predicting locally advanced prostate cancer

OBJECTIVE

To evaluate the efficacy of magnetic resonance spectroscopy imaging (MRSI) for predicting locally advanced prostate cancer (PC).

MATERIALS AND METHODS

Between April 2009 and July 2012, 80 consecutive patients with clinically localized PC had undergone endorectal MRSI before radical retropubic prostatectomy. Clinicopathological parameters, including age, preoperative prostate-specific antigen (PSA), Gleason score (GS) at biopsy, perinural invasion at biopsy, prostate weight at surgery, GS of surgical specimen, and pathological staging were recorded. The MRSI findings were compared with the histopathological findings of the radical prostatectomy. The diagnostic accuracy measures consisting of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) of MRSI, and other variables in the diagnosis of locally advanced PC (Pathology Stages pT3a, pT3b, or pT4) were evaluated.

RESULTS

Sensitivity, specificity, PPV, and NPV of MRSI in detecting locally advanced PC is 42.4%, 93.6%, 82.3%, and 69.8%, respectively [area under the receiver operating characteristic (ROC) curve=0.658, p value <0.0001]. MRSI, cancer-positive core percentage at biopsy, and GS at biopsy are more accurate factors among all the predictive variables in predicting locally advanced PC.

CONCLUSION

MRSI may be considered as a complementary diagnostic modality with high specificity and moderate sensitivity in predicting locally advanced PC. Combination of this modality with other predictive factors helps the surgeon and patient to select an appropriate treatment strategy.

Radiopharmaceuticals as probes to characterize tumour tissue

Tumour cells exhibit several properties that allow them to grow and divide. A number of these properties are detectable by nuclear imaging methods. We discuss crucial tumour properties that can be described by current radioprobe technologies, further discuss areas of emerging radioprobe development, and finally articulate need areas that our field should aspire to develop. The review focuses largely on positron emission tomography and draws upon the seminal 'Hallmarks of Cancer' review article by Hanahan and Weinberg in 2011 placing into context the present and future roles of radiotracer imaging in characterizing tumours.

Rotating frame relaxation imaging of prostate cancer: Repeatability, cancer detection, and Gleason score prediction

PURPOSE

To investigate relaxation along a fictitious field (RAFF) and continuous wave (cw) T1ρ imaging of prostate cancer (PCa) in the terms of repeatability, PCa detection, and characterization.

METHODS

Thirty-six patients (PSA 11.6 ± 7.6 ng/mL, mean ± standard deviation) with histologically confirmed PCa underwent two repeated 3T MR examinations using surface array coils before prostatectomy. Relaxation along fictitious field, cw T1ρ, and T2 relaxation times (TRAFF, T1ρcw, T2) were measured and averaged over regions of interest placed in PCa, normal peripheral zone (PZ), and normal central gland (CG) positioned using whole-mount prostatectomy sections and anatomical T2-weighted images. Receiver operating characteristic curve analysis with area under the curve (AUC) was calculated to distinguish PCa from PZ/CG and PCa with Gleason score (GS) of 3+3 from GS of 3+4/≥ 3+4.

RESULTS

TRAFF and T1ρcw relaxation times were repeatable with coefficients of repeatability as a percentage of median value in the range of 7.8-23.2%. AUC (mean, 95% confidence interval) in the differentiation of PCa with GS of 3+3 from PCa with CS of ≥ 3+4 were 0.88 (0.72-0.99), 0.69 (0.46-0.90), and 0.68 (0.45-0.88), for TRAFF, T1ρcw, and T2, respectively.

CONCLUSION

In quantitative region of interest based analysis, TRAFF outperformed T1ρcw and T2 in PCa detection and characterization.

Preclinical comparison of Al18F- and 68Ga-labeled gastrin-releasing peptide receptor antagonists for PET imaging of prostate cancer

Gastrin-releasing peptide receptor (GRPR) is overexpressed in human prostate cancer and is being used as a target for molecular imaging. In this study, we report on the direct comparison of 3 novel GRPR-targeted radiolabeled tracers: Al(18)F-JMV5132, (68)Ga-JMV5132, and (68)Ga-JMV4168 (JMV5132 is NODA-MPAA-βAla-βAla-[H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2], JMV4168 is DOTA-βAla-βAla-[H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2], and NODA-MPAA is 2-[4-(carboxymethyl)-7-{[4-(carboxymethyl)phenyl]methyl}-1,4,7-triazacyclononan-1-yl]acetic acid).

METHODS

The GRPR antagonist JMV594 (H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) was conjugated to NODA-MPAA for labeling with Al(18)F. JMV5132 was radiolabeled with (68)Ga and (18)F, and JMV4168 was labeled with (68)Ga for comparison. The inhibitory concentration of 50% values for binding GRPR of JMV4168, JMV5132, (nat)Ga-JMV4168, and (nat)Ga-JMV5132 were determined in a competition-binding assay using GRPR-overexpressing PC-3 tumors. The tumor-targeting characteristics of the compounds were assessed in mice bearing subcutaneous PC-3 xenografts. Small-animal PET/CT images were acquired, and tracer biodistribution was determined by ex vivo measurements.

RESULTS

JMV5132 was labeled with (18)F in a novel 1-pot, 1-step procedure within 20 min, without need for further purification and resulting in a specific activity of 35 MBq/nmol. Inhibitory concentration of 50% values (in nM) for GRPR binding of JMV5132, JMV4168, (nat)Ga-JMV5132, (nat)Ga-JMV4168, and Al(nat)F-JMV5132 were 6.8 (95% confidence intervals [CIs], 4.6-10.0), 13.2 (95% CIs, 5.9-29.3), 3.0 (95% CIs, 1.5-6.0), 3.2 (95% CIs, 1.8-5.9), and 10.0 (95% CIs, 6.3-16.0), respectively. In mice with subcutaneous PC-3 xenografts, all tracers cleared rapidly from the blood, exclusively via the kidneys for (68)Ga-JMV4168 and partially hepatobiliary for (68)Ga-JMV5132 and Al(18)F-JMV5132. Two hours after injection, the uptake of (68)Ga-JMV4168, (68)Ga-JMV5132, and Al(18)F-JMV5132 in PC-3 tumors was 5.96 ± 1.39, 5.24 ± 0.29, 5.30 ± 0.98 (percentage injected dose per gram), respectively. GRPR specificity was confirmed by significantly reduced tumor uptake of the 3 tracers after coinjection of a 100-fold excess of unlabeled JMV4168 or JMV5132. Small-animal PET/CT clearly visualized PC-3 tumors, with the highest resolution observed for Al(18)F-JMV5132.

CONCLUSION

JMV5132 could be rapidly and efficiently labeled with (18)F. Al(18)F-JMV5132, (68)Ga-JMV5132, and (68)Ga-JMV4168 all showed comparable high and specific accumulation in GRPR-positive PC-3 tumors. These new PET tracers are promising candidates for future clinical translation.

¹¹C-acetate PET/CT imaging: physiologic uptake, variants, and pitfalls

(11)C-acetate PET is used in the assessment of various cardiologic and oncologic diseases. This article describes the physiologic uptake of (11)C-acetate and presents the common benign findings in different anatomic parts of the body. Salivary glands, tonsils, thyroid, meningeal tuberculoma, meningiomas, and macroadenomas of pituitary gland are sites of mild to moderate tracer uptake in the head and neck region. Parenchymal diseases of the lung and reactive and/or inflammatory mediastinal lymphadenopathies cause benign (11)C-acetate uptake in the thorax. Liver, spleen, pancreas, and rectum show an increased uptake. Urinary tract and prostate gland show faint tracer uptake.

Localized prostate cancer detection with 18F FACBC PET/CT: comparison with MR imaging and histopathologic analysis

PURPOSE

To characterize uptake of 1-amino-3-fluorine 18-fluorocyclobutane-1-carboxylic acid ((18)F FACBC) in patients with localized prostate cancer, benign prostatic hyperplasia (BPH), and normal prostate tissue and to evaluate its potential utility in delineation of intraprostatic cancers in histopathologically confirmed localized prostate cancer in comparison with magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained for this HIPAA-compliant prospective study. Twenty-one men underwent dynamic and static abdominopelvic (18)F FACBC combined positron emission tomography (PET) and computed tomography (CT) and multiparametric (MP) 3-T endorectal MR imaging before robotic-assisted prostatectomy. PET/CT and MR images were coregistered by using pelvic bones as fiducial markers; this was followed by manual adjustments. Whole-mount histopathologic specimens were sliced with an MR-based patient-specific mold. (18)F FACBC PET standardized uptake values (SUVs) were compared with those at MR imaging and histopathologic analysis for lesion- and sector-based (20 sectors per patient) analysis. Positive and negative predictive values for each modality were estimated by using generalized estimating equations with logit link function and working independence correlation structure.

RESULTS

(18)F FACBC tumor uptake was rapid but reversible. It peaked 3.6 minutes after injection and reached a relative plateau at 15-20 minutes (SUVmax[15-20min]). Mean prostate tumor SUVmax(15-20min) was significantly higher than that of the normal prostate (4.5 ± 0.5 vs 2.7 ± 0.5) (P < .001); however, it was not significantly different from that of BPH (4.3 ± 0.6) (P = .27). Sector-based comparison with histopathologic analysis, including all tumors, revealed sensitivity and specificity of 67% and 66%, respectively, for (18)F FACBC PET/CT and 73% and 79%, respectively, for T2-weighted MR imaging. (18)F FACBC PET/CT and MP MR imaging were used to localize dominant tumors (sensitivity of 90% for both). Combined (18)F FACBC and MR imaging yielded positive predictive value of 82% for tumor localization, which was higher than that with either modality alone (P < .001).

CONCLUSION

(18)F FACBC PET/CT shows higher uptake in intraprostatic tumor foci than in normal prostate tissue; however, (18)F FACBC uptake in tumors is similar to that in BPH nodules. Thus, it is not specific for prostate cancer. Nevertheless, combined (18)F FACBC PET/CT and T2-weighted MR imaging enable more accurate localization of prostate cancer lesions than either modality alone.

Electrical property sensing biopsy needle for prostate cancer detection

BACKGROUND

Significant electrical property differences have been demonstrated to exist between malignant and benign prostate tissues. We evaluated how well a custom designed clinically deployable electrical property sensing biopsy needle is able to discriminate between these tissue types in an ex vivo prostate model.

METHODS

An electrical impedance spectroscopy (EIS) sensing biopsy (Bx) needle was developed to record resistive (ρR) and reactive (ρX) components of electrical impedance from 100 Hz to 1 MHz. Standard twelve-core biopsy protocols were followed, in which the EIS-Bx device was used to gauge electrical properties prior to extracting tissue cores through biopsy needle firing from 36 ex vivo human prostates. Histopathological assessment of the cores was statistically compared to the impedance spectrum gauged from each core.

RESULTS

The magnitudes of the mean resistive and reactive components were significantly higher in cancer tissues (P < 0.05). ROC curves showed that ρR at 63.09 kHz was optimal for discriminating cancer from benign tissues; this parameter had 75.4% specificity, 76.1% sensitivity, and ROC AUC of 0.779. Similarly, 251.1 kHz was optimal when using ρX to discriminate cancer from benign tissues; this parameter had a 77.9% specificity, 71.4% sensitivity, and ROC AUC of 0.79.

CONCLUSION

Significant electrical property differences noted between benign and malignant prostate tissues suggest the potential efficacy an EIS-Bx device would provide for cancer detection in a clinical setting. By sensing a greater fraction of the prostate's volume in real-time, the EIS-Bx device has the potential to improve the accuracy of cancer grading and volume estimation made with current biopsy procedures.

Update on positron emission tomography for imaging of prostate cancer

Prostate cancer is the most common non-cutaneous malignancy among men in the Western world, and continues to be a major health problem. Imaging has recently become more important in the clinical management of prostate cancer patients, including diagnosis, staging, choice of optimal treatment strategy, treatment follow up and restaging. Positron emission tomography, a functional and molecular imaging technique, has opened a new field in clinical oncological imaging. The most common positron emission tomography radiotracer, 18F-fluorodeoxyglucose, has been limited in imaging of prostate cancer. Recently, however, other positron emission tomography tracers, such as 11C-acetate and 11C- or (18) F-choline, have shown promising results. In the present review article, we overview the potential and current use of positron emission tomography or positron emission tomography/computed tomography imaging employing the four most commonly used positron emission tomography radiotracers, 18F-fluorodeoxyglucose, 11C-acetate and 11C- or 18F-choline, for imaging evaluation of prostate cancer.

In vivo imaging of prostate cancer using [68Ga]-labeled bombesin analog BAY86-7548

PURPOSE

A novel [(68)Ga]-labeled DOTA-4-amino-1-carboxymethyl-piperidine-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 peptide (BAY86-7548) having high affinity to bombesin receptor subtype II to detect primary and metastatic prostate carcinoma using positron emission tomography/computed tomography (PET/CT) was synthesized and evaluated for prostate cancer.

EXPERIMENTAL DESIGN

In this first human study with BAY86-7548, 14 men scheduled for radical prostatectomy (n = 11) or with biochemical recurrence after surgery or hormonal therapy (n = 3) were enrolled. The patients received an intravenous injection of BAY86-7548 followed by over 60-minute dynamic imaging of prostate gland (n = 10) and/or subsequent whole-body imaging (n = 14). The visual assessment of PET/CT images included evaluation of intraprostatic (12 subsextants) and pelvic nodal uptake of BAY86-7548 in 11 surgical patients and detection of potential metastatic foci in all patients. In patients with biochemical recurrence, results were compared with those of either [(11)C]-acetate (n = 2) or [(18)F]-fluoromethylcholine (n = 1) PET/CT.

RESULTS

We found a sensitivity, specificity, and accuracy of 88%, 81% and 83%, respectively, for detection of primary PCa and sensitivity of 70% for metastatic lymph nodes using histology as gold standard. BAY86-7548 correctly detected local recurrence in prostate bed and showed nodal relapse in accordance with [(11)C]-acetate PET/CT in 2 patients with biochemical relapse. In the third hormone refractory patient, BAY86-7548 failed to show multiple bone metastases evident on [(18)F]-fluoromethylcholine PET/CT.

CONCLUSION

BAY86-7548 PET/CT is a promising molecular imaging technique for detecting intraprostatic prostate cancer.

Functional and molecular imaging: applications for diagnosis and staging of localised prostate cancer

Prostate cancer is currently the most common solid organ cancer type among men in the Western world. Currently, all decision-making algorithms and nomograms rely on demographics, clinicopathological data and symptoms. Such an approach can easily miss significant cancers while detecting many insignificant cancers. In this review, novel functional and molecular imaging techniques used in the diagnosis and staging of localised prostate cancer and their effect on treatment decisions are discussed.

Functional and molecular imaging of localized and recurrent prostate cancer

Prostate cancer is the most common malignancy among American men. Imaging of localized and recurrent prostate cancer is challenging since conventional imaging techniques are limited. New imaging techniques such as multiparametric MRI and PET with targeted tracers have been investigated extensively in the last decade. As a result, the role of novel imaging techniques for the detection of localized and recurrent prostate cancer has recently expanded. In this review, novel functional and molecular imaging techniques used in the management of localized and recurrent prostate cancer are discussed.

Spatially matched in vivo and ex vivo MR metabolic profiles of prostate cancer -- investigation of a correlation with Gleason score

MR metabolic profiling of the prostate is promising as an additional diagnostic approach to separate indolent from aggressive prostate cancer. The objective of this study was to assess the relationship between the Gleason score and the metabolic biomarker (choline + creatine + spermine)/citrate (CCS/C) measured by ex vivo high-resolution magic angle spinning MRS (HR-MAS MRS) and in vivo MRSI, and to evaluate the correlation between in vivo- and ex vivo-measured metabolite ratios from spatially matched prostate regions. Patients (n = 13) underwent in vivo MRSI prior to radical prostatectomy. A prostate tissue slice was snap-frozen shortly after surgery and the locations of tissue samples (n = 40) collected for ex vivo HR-MAS were matched to in vivo MRSI voxels (n = 40). In vivo MRSI was performed on a 3T clinical MR system and ex vivo HR-MAS on a 14.1T magnet. Relative metabolite concentrations were calculated by LCModel fitting of in vivo spectra and by peak integration of ex vivo spectra. Spearman's rank correlations (ρ) between CCS/C from in vivo and ex vivo MR spectra, and with their corresponding Gleason score, were calculated. There was a strong positive correlation between the Gleason score and CCS/C measured both in vivo and ex vivo (ρ = 0.77 and ρ = 0.69, respectively; p < 0.001), and between in vivo and ex vivo metabolite ratios from spatially matched regions (ρ = 0.67, p < 0.001). Our data indicate that MR metabolic profiling is a potentially useful tool for the assessment of cancer aggressiveness. Moreover, the good correlation between in vivo- and ex vivo-measured CCS/C demonstrates that our method is able to bridge MRSI and HR-MAS molecular analysis.

Magnetic resonance imaging for prostate cancer clinical application

As prostate cancer is a biologically heterogeneous disease for which a variety of treatment options are available, the major objective of prostate cancer imaging is to achieve more precise disease characterization. In clinical practice, magnetic resonance imaging (MRI) is one of the imaging tools for the evaluation of prostate cancer, the fusion of MRI or dynamic contrast-enhanced MRI (DCE-MRI) with magnetic resonance spectroscopic imaging (MRSI) is improving the evaluation of cancer location, size, and extent, while providing an indication of tumor aggressiveness. This review summarizes the role of MRI in the application of prostate cancer and describes molecular MRI techniques (including MRSI and DCE-MRI) for aiding prostate cancer management.

Novel targeted nuclear imaging agent for gastric cancer diagnosis: glucose-regulated protein 78 binding peptide-guided 111In-labeled polymeric micelles

Increased expression of cellular membrane bound glucose-regulated protein 78 (GRP78) is considered to be one of the biomarkers for gastric cancers. Therefore, peptides or molecules with specific recognition to GRP78 can act as a guiding probe to direct conjugated imaging agents to localized cancers. Based on this rationale, GRP78-guided polymeric micelles were designed and manufactured for nuclear imaging detection of tumors. Thiolated GRP78 binding peptide (GRP78BP) was first labeled with maleimide-terminated poly(ethylene glycol)– poly(ɛ-caprolactone) and then mixed with diethylenetriaminepentaacetic acid (DTPA)-linked poly(ethylene glycol)–poly(ɛ-caprolactone) to form DTPA/GRP78BP-conjugated micelles. The coupling efficiency of micelles with radioisotope indium-111 (¹¹¹In) was measured and analyzed by instant thin layer chromatography. The coupling efficiency of DTPA-conjugated micelles and DTPA/GRP78BP-conjugated micelles with ¹¹¹In was 85% and 93%, respectively. For characterization and trace imaging, the radioisotope ¹¹¹In-targeting tumors were detected and imaged in a xenograft murine model using nano single photon emission computed tomography/computed tomography. The results revealed that the radioactive intensity measured in the animals administered with GRP78BP-guided ¹¹¹In-labeled micelles was statistically higher than that in animals administered with ¹¹¹In-labeled micelles, demonstrating that GRP78BP more than doubled the accumulation of micelles to the tumor tissue (P < 0.05). The results indicate that the gastric cancer biomarker GRP78 is a probing target in the application of nuclear imaging for tumor diagnosis. This novel GRP78BP-guided micelle agent may be applied in clinical practice to complement the histological diagnosis.

Functional imaging for prostate cancer: therapeutic implications

Functional radionuclide imaging modalities, now commonly combined with anatomical imaging modalities computed tomography (CT) or magnetic resonance imaging (single photon emission computed tomography [SPECT]/CT, positron emission tomography [PET]/CT, and PET/magnetic resonance imaging), are promising tools for the management of prostate cancer, particularly for therapeutic implications. Sensitive detection capability of prostate cancer using these imaging modalities is one issue; however, the treatment of prostate cancer using the information that can be obtained from functional radionuclide imaging techniques is another challenging area. There are not many SPECT or PET radiotracers that can cover the full spectrum of the management of prostate cancer from initial detection to staging, prognosis predictor, and all the way to treatment response assessment. However, when used appropriately, the information from functional radionuclide imaging improves, and sometimes significantly changes, the whole course of the cancer management. The limitations of using SPECT and PET radiotracers with regard to therapeutic implications are not so much different from their limitations solely for the task of detecting prostate cancer; however, the specific imaging target and how this target is reliably imaged by SPECT and PET can potentially make significant impact in the treatment of prostate cancer. Finally, although the localized prostate cancer is considered manageable, there is still significant need for improvement in noninvasive imaging of metastatic prostate cancer, in treatment guidance, and in response assessment from functional imaging, including radionuclide-based techniques. In this review article, we present the rationale of using functional radionuclide imaging and the therapeutic implications for each of radionuclide imaging agent that have been studied in human subjects.

Choline PET and PET/CT in Primary Diagnosis and Staging of Prostate Cancer

PET and PET/CT using [(11)C]- and [(18)F]-labelled choline derivates is increasingly being used for imaging of primary and recurrent prostate cancer. While PET and PET/CT with [(11)C]- and [(18)F]-labelled choline derivates in patients suffering from biochemical recurrence of prostate cancer has been examined in many studies that demonstrate an increasing importance, its role in the primary staging of prostate cancer is still a matter of debate.Morphological and functional imaging techniques such as CT, MRI and TRUS have demonstrated only limited accuracy for the diagnosis of primary prostate cancer. Molecular imaging with PET and PET/CT could potentially increase accuracy to localize primary prostate cancer. A considerable number of studies have examined the value of PET/CT with [(11)C]- and [(18)F]- labelled choline derivates for the diagnosis of primary prostate cancer with mixed results. Primary prostate cancer can only be detected with moderate sensitivity using [(11)C]- and [(18)F]choline PET and PET/CT. The detection rate depends on the tumour configuration. Detection is also limited by a considerable number of microcarcinomas that cannot be detected due to partial volume effects. Therefore small and in part rind-like tumours can often not be visualized. Furthermore, the differentiation between benign changes like prostatitis, high-grade intraepithelial neoplasia (HGPIN) or prostatic hyperplasia is not always possible. Therefore, at the present time, the routine use of PET/CT with [(11)C]- and [(18)F]-labelled choline derivates cannot be recommended as a first-line screening procedure for primary prostate cancer in men at risk. A potential application of choline PET and PET/CT may be to increase the detection rate of clinically suspected prostate cancer with multiple negative prostate biopsies, for example in preparation of a focused re-biopsy and may play a role in patient stratification with respect to primary surgery and radiation therapy in the future.

Improved detection of localized prostate cancer using co-registered MRI and 11C-acetate PET/CT

OBJECTIVES

We aimed to study the ability of contrast enhanced MRI at 1.5 T and 11C-acetate PET/CT, both individually and using fused data, to detect localized prostate cancer.

METHODS

Thirty-six men with untreated prostate cancer and negative for metastatic disease on pelvic CT and bone scan were prospectively enrolled. A pelvic 11C-acetate PET/CT scan was performed in all patients, and a contrast enhanced MRI scan in 33 patients (6 examinations using both endorectal coil and surface coils, and 27 examinations using surface coils only). After the imaging studies 10 patients underwent prostatectomy and 26 were treated by image guided external beam radiation treatment. Image fusion of co-registered PET and MRI data was performed based on anatomical landmarks visible on CT and MRI using an advanced in-house developed software package. PET/CT, MRI and fused PET/MRI data were evaluated visually and compared with biopsy findings on a lobar level, while a sextant approach was used for patients undergoing prostatectomy.

RESULTS

When using biopsy samples as method of reference, the sensitivity, specificity and accuracy for visual detection of prostate cancer on a lobar level by contrast enhanced MRI was 85%, 37%, 73% and that of 11C-acetate PET/CT 88%, 41%, 74%, respectively. Fusion of PET with MRI data increased sensitivity, specificity and accuracy to 90%, 72% and 85%, respectively.

CONCLUSIONS

Fusion of sequentially obtained PET/CT and MRI data for the localization of prostate cancer is feasible and superior to the performance of each individual modality alone.

11C-Acetate PET/CT in localized prostate cancer: a study with MRI and histopathologic correlation

This work characterizes the uptake of (11)C-acetate in prostate cancer (PCa), benign prostate hyperplasia, and normal prostate tissue in comparison with multiparametric MRI, whole-mount histopathology, and clinical markers to evaluate the potential utility of (11)C-acetate for delineating intraprostatic tumors in a population of patients with localized PCa.

METHODS

Thirty-nine men with presumed localized PCa underwent dynamic-static abdominal-pelvic (11)C-acetate PET/CT for 30 min and 3-T multiparametric MRI before prostatectomy. PET/CT images were registered to MR images using pelvic bones for initial rotation-translation, followed by manual adjustments to account for prostate motion and deformation from the MRI endorectal coil. Whole-mount pathology specimens were sectioned using an MRI-based patient-specific mold resulting in improved registration between the MRI, PET, and pathology. (11)C-acetate PET standardized uptake values were compared with multiparametric MRI and pathology.

RESULTS

(11)C-acetate uptake was rapid but reversible, peaking at 3-5 min after injection and reaching a relative plateau at approximately 10 min. The average maximum standardized uptake value (10-12 min) of tumors was significantly higher than that of normal prostate tissue (4.4 ± 2.05 [range, 1.8-9.2] vs. 2.1 ± 0.94 [range, 0.7-3.4], respectively; P < 0.001); however, it was not significantly different from that of benign prostatic hyperplasia (4.8 ± 2.01 [range, 1.8-8.8]). A sector-based comparison with histopathology, including all tumors greater than 0.5 cm, revealed a sensitivity and specificity of 61.6% and 80.0%, respectively, for (11)C-acetate PET/CT and 82.3% and 95.1%, respectively, for MRI. The (11)C-acetate accuracy was comparable to that of MRI when only tumors greater than 0.9 cm were considered. In a small cohort (n = 9), (11)C-acetate uptake was independent of fatty acid synthase expression using immunohistochemistry.

CONCLUSION

(11)C-acetate PET/CT demonstrates higher uptake in tumor foci than in normal prostate tissue; however, (11)C-acetate uptake in tumors is similar to that in benign prostate hyperplasia nodules. Although (11)C-acetate PET/CT is not likely to have utility as an independent modality for evaluation of localized PCa, the high uptake in tumors may make it useful for monitoring focal therapy when tissue damage after therapy may limit anatomic imaging methods.

Targeted near-infrared imaging of the erythropoietin receptor in human lung cancer xenografts

The putative presence of the erythropoietin receptor (EpoR) on human cancer cells has given rise to controversial discussion about the use of recombinant human erythropoietin (rhuEpo) for treatment of patients with chemotherapy-induced anemia. In vivo analysis of the EpoR status in tumors could help in elucidating the role of erythropoietin in cancer. Thus, the aim of this study was to develop a targeted EpoR probe for the investigation of EpoR expression in human lung cancer xenografts by fluorescence-mediated tomography.

METHODS

Epo-Cy5.5 was generated by coupling Cy5.5 to rhuEpo. In vitro binding assays were performed using the EpoR-positive non-small cell lung cancer (NSCLC) cell lines A549 (lower EpoR expression) and H838 (higher EpoR expression), the EpoR-negative cell line H2030, and EpoR/EGFP-overexpressing HeLa cells. In vivo specificity of Epo-Cy5.5 was confirmed by competition analyses using micro-CT/fluorescence-mediated tomography fusion imaging. Biodistribution was analyzed over 50 h after injection. Binding of Epo-Cy5.5 was validated on tumor cryosections.

RESULTS

After intravenous injection, the probe was rapidly cleared from the circulation. An accumulation was observed in liver and kidneys, with a maximum at 7 h after injection followed by a decline, indicating renal excretion. Almost constant accumulation of Epo-Cy5.5 was found in bone marrow and tumors, indicating specific receptor binding. The probe allowed the discrimination between H838 with higher EpoR expression (89.54 ± 15.91 nM at 25 h) and A549 tumors with lower EpoR expression (60.45 ± 14.59 nM at 25 h, P < 0.05). Tumor accumulation of Epo-Cy5.5 could be significantly reduced by adding unlabeled rhuEpo (P < 0.05 at 4, 7, and 24 h). In vitro validation confirmed specific binding of Epo-Cy5.5 to the tumor cells, and this binding correlated with the EpoR expression level. Binding was also observed on endothelial cells. Vessel density and Epo-Cy5.5 binding on endothelial cells were comparable.

CONCLUSION

Epo-Cy5.5 allows the longitudinal analysis of EpoR expression in tumors and thereby can investigate the influence of erythropoietin on EpoR expression, tumor growth, and angiogenesis.

Feasibility of 11C-acetate PET/CT for imaging of fatty acid synthesis in the atherosclerotic vessel wall

Fatty acids are a common constituent of atherosclerotic plaque and may be synthesized in the plaque itself. Fatty acid synthesis requires acetyl-coenzyme-A (CoA) as a main substrate, which is produced from acetate. Currently, (11)C-acetate PET/CT is used for the evaluation of malignancies. There are no data concerning its potential for the characterization of atherosclerotic plaque. Therefore, the purpose of the present study was to examine the prevalence, distribution, and topographic relationship of arterial (11)C-acetate uptake and vascular calcification in major arteries.

METHODS

Thirty-six patients were examined by whole-body (11)C-acetate PET/CT. Tracer uptake in various arterial segments was analyzed both qualitatively and semiquantitatively by measuring the blood-pool-corrected standardized uptake value (target-to-background ratio). CT images were used to measure calcified plaque burden.

RESULTS

(11)C-acetate uptake was observed at 220 sites in 32 (88.8%) of the 36 study patients, and mean target-to-background ratio was 2.5 ± 1.0. Calcified atherosclerotic lesions were observed at 483 sites in 30 (83.3%) patients. Sixty-four (29.1%) of the 220 lesions with marked (11)C-acetate uptake were colocalized with arterial calcification. However, only 13.3% of all arterial calcification sites demonstrated increased radiotracer accumulation.

CONCLUSION

Our data indicate the feasibility of using (11)C-acetate PET/CT for imaging of fatty acid synthesis in the atherosclerotic vessel wall. This study provides a rationale to incorporating (11)C-acetate PET into further preclinical and clinical studies to obtain new insights into fatty acid synthesis in atherosclerotic lesions and to evaluate whether it may be used to monitor pharmacologic intervention with fatty acid synthase inhibitors.

Underestimation of Gleason score at prostate biopsy reflects sampling error in lower volume tumours

OBJECTIVE

• To determine the influence of tumour and prostate gland volumes on the underestimation of prostate cancer Gleason score in diagnostic core biopsies.

PATIENTS AND METHODS

• Patients undergoing radical prostatectomy with matched diagnostic biopsies were identified from a prospectively recorded database. • Tumour volumes were measured in serial whole-mount sections with image analysis software as part of routine histological assessment. • Differences in various metrics of tumour and prostate volume between upgraded tumours and tumours concordant for the lower or higher grade were analysed.

RESULTS

• In all, 684 consecutive patients with Gleason score 6 or 7 prostate cancer on diagnostic biopsy were identified. • Of 298 patients diagnosed with Gleason 6 tumour on biopsy, 201 (67.4%) were upgraded to Gleason 7 or higher on final pathology. Similarly, of 262 patients diagnosed with Gleason 3 + 4 = 7 prostate cancer on initial biopsy, 60 (22.9%) were upgraded to Gleason score 4 + 3 = 7 or higher. • Tumours upgraded from Gleason 6 to 7 had a significantly lower index tumour volume (1.73 vs 2 mL, P= 0.029), higher calculated prostate volume (41.6 vs 39 mL, P= 0.017) and lower relative percentage of tumour to benign glandular tissue (4.3% vs 5.9%, P= 0.001) than tumours concordant for the higher grade. • Similarly, tumours that were Gleason score 3 + 4 on biopsy and upgraded on final pathology to 4 + 3 were significantly smaller as measured by both total tumour volume (2.3 vs 3.3 mL, P= 0.005) and index tumour volume (2.2 vs 3, P= 0.027) and occupied a smaller percentage of the gland volume (6.3% vs 8.9%, P= 0.017) compared with tumours concordant for the higher grade. • On multivariate analysis, lower prostate weight (hazard ratio 0.97, 95% confidence interval 0.96-0.99, P < 0.001) and larger total tumour volume (hazard ratio 1.87, 95% confidence interval 1.4-2.6, P < 0.001) independently predicted an upgrade in Gleason score from 6 to 7. In tumours upgraded from biopsy Gleason 3 + 4, only higher index tumour volume (hazard ratio 3.1, 95% confidence interval 1.01-9.3, P= 0.048) was a significant predictor of upgrading on multivariate analysis.

CONCLUSIONS

• Under-graded tumours are significantly smaller than tumours concordant for the higher grade, indicating that incomplete tumour sampling plays a significant role in Gleason score assignment error. • Surrogate measures of tumour volume may predict those at greatest risk of Gleason score upgrade.

In vivo assessment of prostate cancer aggressiveness using magnetic resonance spectroscopic imaging at 3 T with an endorectal coil

BACKGROUND

One of the most important clinical challenges in prostate cancer (PCa) management is an in vivo assessment of cancer aggressiveness.

OBJECTIVE

To validate the performance of magnetic resonance (MR) spectroscopic imaging (MRSI) of the prostate at 3 T for the purpose of assessing tumour aggressiveness based on the ratio of choline plus creatine to citrate (Cho+Cr/Cit) and of choline to creatine (Cho/Cr), using the Gleason score of the radical prostatectomy (RP) specimen as the gold standard.

DESIGN, SETTING, AND PARTICIPANTS

A total of 43 biopsy-proven PCa patients with 53 clinically relevant tumour foci were retrospectively included in this study.

MEASUREMENTS

Patients underwent MR imaging and MRSI examination followed by RP. From MRSI, all spectroscopy voxels containing tumour were selected by a radiologist guided by the prostatectomy histopathology map only. For each tumour, two spectroscopists determined the maximum Cho+Cr/Cit, Cho/Cr, and malignancy rating using a standardised threshold approach, incorporating both metabolic ratios. The maximum Cho+Cr/Cit, Cho/Cr, and malignancy ratings showed a relation to tumour aggressiveness and so were used to differentiate among tumour aggressiveness classes.

RESULTS AND LIMITATIONS

The maximum Cho+Cr/Cit ratio, maximum Cho/Cr ratio, and malignancy rating of a standardised threshold approach separated low-grade from higher-grade tumours, with areas under the receiver operating characteristic (ROC) curves of 0.70, 0.74, and 0.78, respectively.

CONCLUSIONS

MRSI offers possibilities for an in vivo, noninvasive assessment of PCa aggressiveness. The combination of the different metabolite ratios was used with promising results for discrimination among different aggressiveness classes.

A PET/CT Directed, 3D Ultrasound-Guided Biopsy System for Prostate Cancer

Prostate cancer affects 1 in 6 men in the USA. Systematic transrectal ultrasound (TRUS)-guided biopsy is the standard method for a definitive diagnosis of prostate cancer. However, this "blind" biopsy approach can miss at least 20% of prostate cancers. In this study, we are developing a PET/CT directed, 3D ultrasound image-guided biopsy system for improved detection of prostate cancer. In order to plan biopsy in three dimensions, we developed an automatic segmentation method based wavelet transform for 3D TRUS images of the prostate. The segmentation was tested in five patients with a DICE overlap ratio of more than 91%. In order to incorporate PET/CT images into ultrasound-guided biopsy, we developed a nonrigid registration algorithm for TRUS and PET/CT images. The registration method has been tested in a prostate phantom with a target registration error (TRE) of less than 0.4 mm. The segmentation and registration methods are two key components of the multimodality molecular image-guided biopsy system.