Value of 11C-choline PET and PET/CT in patients with suspected prostate cancer

The Evolving Role of 18F-FDG PET/CT in Diagnosis and Prognosis Prediction in Progressive Prostate Cancer

Positron emission tomography/computed tomography (PET/CT) is widely used in prostate cancer to evaluate the localized tumor burden and detect symptomatic metastatic lesions early. ¹⁸F-FDG is the most used tracer for oncologic imaging, but it has limitations in detecting early-stage prostate cancer. ⁶⁸Ga-PSMA is a new tracer that has high specificity and sensibility in detecting local and metastatic tumors. But with the progression of prostate cancer, the enhancement of glucose metabolism in progressive prostate cancer provides a chance for ¹⁸F-FDG. This review focuses on PET/CT in the detection and prognosis of prostate cancer, summarizing the literature on ¹⁸F-FDG and ⁶⁸Ga-PSMA in prostate cancer and highlighting that ¹⁸F-FDG has advantages in detecting local recurrence, visceral and lymph node metastases compared to ⁶⁸Ga-PSMA in partial progressive prostate cancer and castration-resistant prostate cancer patients. We emphasize ¹⁸F-FDG PET/CT can compensate for the weakness of ⁶⁸Ga-PSMA PET/CT in progressive prostate cancer.

18F-choline PET/computed tomography and clinical parameters in the detection of significant prostate cancer in patients with increased prostate-specific antigen levels and previous negative biopsies

OBJECTIVES

The aim of this study is to assess the value of the F-choline PET/computed tomography (CT) in predicting significant prostate cancer (sPCa) in patients with persistently increased prostate-specific antigen (PSA) levels and previous negative biopsies. To study the possible predictive added value of F-choline PET/CT to clinical variables and biomarkers derived from PSA in detecting sPCa.

METHODS

We evaluated patients who underwent F-choline PET/CT because of ongoing suspicion of prostate cancer (PCa) due to elevated PSA levels (4-20 ng/mL) and at least one previous negative or no conclusive prostate biopsy for PCa. Age, PSA, free PSA, free/total PSA ratio, PSA velocity, PSA doubling time, PSA density and score risk were obtained. F-choline PET/CT was classified as negative/positive (PET-categorical). Additionally, we subclassified F-choline PET/CT according to the radiotracer uptake patterns (PET-pattern). The reference standard was the histological confirmation. Accuracy of PET/CT was evaluated. Univariate and multivariate logistic regression analyses were performed for metabolic and clinical variables.

RESULTS

A total of 78 patients were included in our study, 23 had PCa (15 with sPCa). The PET pattern showed the highest accuracy and was the most powerful predictor of sPCa. In this research, the prediction of sPCa was improved combining PET pattern and score risk.

CONCLUSION

F-choline PET/CT is a potential tool for predicting sPCa in patients with persistently increased PSA levels and previous negative biopsies, and also it could improve the performance of score risk in predicting sPCa.

Kinetic analysis of dominant intraprostatic lesion of prostate cancer using quantitative dynamic [18F]DCFPyL-PET: comparison to [18F]fluorocholine-PET

Purpose

Identification of the dominant intraprostatic lesion(s) (DILs) can facilitate diagnosis and treatment by targeting biologically significant intra-prostatic foci. A PSMA ligand, [¹⁸F]DCFPyL (2-(3-{1-carboxy-5-[(6-[¹⁸F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid), is better than choline-based [¹⁸F]FCH (fluorocholine) in detecting and localizing DIL because of higher tumour contrast, particularly when imaging is delayed to 1 h post-injection. The goal of this study was to investigate whether the different imaging performance of [¹⁸F]FCH and [¹⁸F]DCFPyL can be explained by their kinetic behaviour in prostate cancer (PCa) and to evaluate whether DIL can be accurately detected and localized using a short duration dynamic positron emission tomography (PET).

Methods

19 and 23 PCa patients were evaluated with dynamic [¹⁸F]DCFPyL and [¹⁸F]FCH PET, respectively. The dynamic imaging protocol with each tracer had a total imaging time of 22 min and consisted of multiple frames with acquisition times from 10 to 180 s. Tumour and benign tissue regions identified by sextant biopsy were compared using standardized uptake value (SUV) and tracer kinetic parameters from kinetic analysis of time-activity curves.

Results

For [¹⁸F]DCFPyL, logistic regression identified K_i and k₄ as the optimal model to discriminate tumour from benign tissue (84.2% sensitivity and 94.7% specificity), while only SUV was predictive for [¹⁸F]FCH (82.6% sensitivity and 87.0% specificity). The higher k₃ (binding) of [¹⁸F]FCH than [¹⁸F]DCFPyL explains why [¹⁸F]FCH SUV can differentiate tumour from benign tissue within minutes of injection. Superior [¹⁸F]DCFPyL tumour contrast was due to the higher k₄/k₃ (more rapid washout) in benign tissue compared to tumour tissue.

Conclusions

DIL was detected with good sensitivity and specificity using 22-min dynamic [¹⁸F]DCFPyL PET and avoids the need for delayed post-injection imaging timepoints. The dissimilar in vivo kinetic behaviour of [¹⁸F]DCFPyL and [¹⁸F]FCH could explain their different SUV images.

Clinical Trial Registration NCT04009174 (ClinicalTrials.gov).

Development of Novel PSMA Ligands for Imaging and Therapy with Copper Isotopes

Prostate-specific membrane antigen (PSMA)-binding tracers have been shown to be promising agents for the specific targeting of prostate tumors. On labeling with the short-lived isotopes ¹⁸F and ⁶⁸Ga, excellent molecular imaging performance is achieved. This potential could be further exploited using long-lived isotopes. Because of the favorable half-life of ⁶⁴Cu, tracers labeled with this PET nuclide could solve logistic problems. Moreover, this isotope provides a theranostic pair with the therapeutic copper isotope ⁶⁷Cu. Hence, 9 novel tracers that combine dedicated copper chelators with the PSMA-specific urea-based binding motif were developed. Methods: The precursors were obtained by solid-phase synthesis. The purity and molecular weight of the PSMA ligands were confirmed by high-performance liquid chromatography and liquid chromatography-mass spectrometry. The compounds were labeled with ⁶⁴Cu, with a radiolabeling yield of more than 99%. Competitive cell binding assays and internalization assays were performed with C4-2 cells, a subline of the PSMA-positive cell line LNCaP (human lymph node carcinoma of the prostate). In vitro serum stability, the stability of ⁶⁴Cu-CA003 in blood, and the in vivo fate of neat ⁶⁴Cu-chloride or ⁶⁴Cu-CA003 were determined to prove whether the stability of the radiolabeled compounds is sufficient to ensure no significant loss of copper during the targeting process. For PET imaging and biodistribution studies, a C4-2 tumor-bearing mouse model was used. Results: The radiolabeled ⁶⁴Cu-PSMA ligands showed high serum stability. All PSMA ligands showed high inhibition potencies, with equilibrium inhibition constants in the low nanomolar range. ⁶⁴Cu-CA003 and ⁶⁴Cu-CA005 showed high internalization ratios (34.6% ± 2.8 and 18.6% ± 4.4, respectively). Both the in vitro serum stability determination and the in vivo characterization of the main radiolabeled compounds confirmed that, except for ⁶⁴Cu-PSMA-617, all compounds showed high serum stability within the observation period of 24 h. Small-animal PET imaging demonstrated high tumor uptake within 20 min. Organ distribution studies confirmed high specific uptake in the tumor, with 30.8 ± 12.6 percentage injected dose (%ID)/g at 1 h after injection. Rapid clearance from the kidneys was observed-a decrease from 67.0 ± 20.9 %ID/g at 1 h after injection to 7.5 ± 8.51 %ID/g at 24 h after injection (in the case of CA003). The performance of CA003, the compound with the best preclinical properties, was assessed in a first patient. In line with its preclinical data, PET imaging resulted in clear visualization of the cancer lesions, with high contrast. Conclusion: The ⁶⁴Cu-labeled PSMA ligands are promising agents to target PSMA and visualize PSMA-positive tumor lesions as shown in preclinical evaluation by small-animal PET studies, organ distribution, and a patient application. Most importantly, the images obtained at 20 h enabled delineation of unclear lesions, showing that the compounds fulfill the prerequisite for dosimetry in the course of therapy planning with ⁶⁷Cu. Thus, we suggest clinical use of copper-labeled CA003 for diagnostics and radiotherapy of prostate cancer.

Dynamic 11C-Choline PET / CT for the primary diagnosis of prostate cancer

OBJECTIVES

To test the ability of dynamic 11C-PET / CT to discriminate cancerous tissue from background tissue in patients with localized prostate cancer.

MATERIALS AND METHODS

Twenty-four consecutive patients with prostate cancer were prospectively evaluated with dynamic 11C-choline PET / CT prior to radical prostatectomy. The PET / CT scan was divided into 18 sequences of 5 seconds each, followed by 9 sequences of 60 seconds each. Whole-mount sections of harvested prostates served as reference standards. Volumes of interest were positioned on the dynamic PET / CT images and the following quantitative variables were calculated: perfusion coefficient (K1), washout constant (K2), area under the curve (AUC) at 175 and 630 seconds, and average and maximum standardized uptake values (SUVavg, and SUVmax). Wilcoxon signed-ranks test was used to compare benign and cancerous areas of the prostate.

RESULTS

Areas of cancerous tissue were characterized by higher SUVavg and SUVmax than areas of benign tissue (3.67 ± 2.7 vs. 2.08 ± 1.3 and 5.91 ± 4.4 vs. 3.71 ± 3.7, respectively, P < 0.001), in addition to a higher K1 (0.95 ± 0.58 vs. 0.43 ± 0.24, P < 0.001) and greater cumulative tracer uptake, represented by the AUC at 175 and 630 seconds (P <0.001). No associations were found between dynamic parameters and preoperative prostate specific antigen level or Gleason score.

CONCLUSIONS

In this pilot study, 11C-choline PET / CT demonstrated increased tracer uptake with higher values of static and dynamic parameters in areas of prostate cancer compared to areas of benign tissue. Larger studies are warranted to validate these results and examine the potential applicability of 11C-choline dynamic PET / CT for the diagnosis of prostate cancer.

Anatomic and Molecular Imaging in Prostate Cancer

Prostate cancer is characterized by a complex set of heterogeneous disease states. This review aims to describe how imaging has been studied within each specific state. As physicians transition into an era of precision medicine, multiparametric magnetic resonance imaging (mpMRI) is proving to be a powerful tool leading the way for a paradigm shift in the diagnosis and management of localized prostate cancer. With further research and development, molecular imaging modalities will likely change the way we approach recurrent and metastatic disease. Given the range of possible oncological progression patterns, a thorough understanding of the underlying carcinogenesis, as it relates to imaging, is a requisite if we are to appropriately manage prostate cancer in future decades.

Quantitative 18F-fluorocholine positron emission tomography for prostate cancer: correlation between kinetic parameters and Gleason scoring

BACKGROUND

The use of radiolabeled choline as a positron emission tomography (PET) agent for imaging primary tumors in the prostate has been evaluated extensively over the past two decades. There are, however, conflicting reports of its sensitivity and the relationship between choline PET imaging and disease staging is not fully understood. Moreover, relatively few studies have investigated the correlation between tracer uptake and histological tumor grade. This work quantified 18F-fluorocholine in tumor and healthy prostate tissue using pharmacokinetic modeling and stratified uptake parameters by histology grade. Additionally, the effect of scan time on the estimation of the kinetic exchange rate constants was evaluated, and the tracer influx parameters from full compartmental analysis were compared to uptake values quantified by Patlak and standardized uptake value (SUV) analyses. 18F-fluorocholine was administered as a 222 MBq bolus injection to ten patients with biopsy-confirmed prostate tumors, and dynamic PET data were acquired for 60 min. Image-derived arterial input functions were scaled by discrete blood samples, and a 2-tissue, 4-parameter model accounting for blood volume (2T4k+Vb) was used to perform fully quantitative compartmental modeling on tumor, healthy prostate, and muscle tissue. Subsequently, all patients underwent radical prostatectomy, and histological analyses were performed on the prostate specimens; kinetic parameters for tumors were stratified by Gleason score. Correlations were investigated between compartmental K 1 and K i parameters and SUV and Patlak slope; the effect of scan time on parameter bias was also evaluated.

RESULTS

Choline activity curves in seven tumors, eight healthy prostate regions, and nine muscle regions were analyzed. Net tracer influx was generally higher in tumor relative to healthy prostate, with the values in the highest grade tumors markedly higher than those in lower grade tumors. Influx terms from Patlak and full compartmental modeling showed good correlation within individual tissue groups. Kinetic parameters calculated from the entire 60-min scan data were accurately reproduced from the first 30 min of acquired data (R 2 ≈ 0.9).

CONCLUSIONS

Strong correlations were observed between K i and Patlak slope in tumor tissue, and K 1 and SUV were also correlated but to a lesser degree. Reliable estimates of all kinetic parameters can be achieved from the first 30 min of dynamic 18F-choline data. Although SUV, K 1, K i, and Patlak slope were found to be poor differentiators of low-grade tumor compared to healthy prostate tissue, they are strong indicators of aggressive disease.

Targeted 11C-choline PET-CT/TRUS software fusion-guided prostate biopsy in men with persistently elevated PSA and negative mpMRI after previous negative biopsy

Background

We evaluated the feasibility and accuracy of 11C–choline PET-CT/TRUS fusion-guided prostate biopsy in men with persistently elevated PSA and negative mpMRI or contraindication to MRI, after previous negative biopsy. Clinical data were part of a prospective on-going observational clinical study: “Diagnostic accuracy of target mpMRI/US fusion biopsy in patients with suspected prostate cancer after initial negative biopsy”. Patients with a negative biopsy and negative mpMRI (PI-RADS v.2 < 3) or absolute contraindications to MRI and persistently elevated PSA, were included. All patients underwent 11C–choline PET with dedicated acquisition of the pelvis and PET-CT/TRUS-guided prostate biopsy by Bio-Jet™ fusion system (D&K Technologies, Germany). The primary endpoint was to assess the accuracy of 11C–choline PET-CT to determine the presence and the topographical distribution of PCa.

Results

Overall, 15 patients (median age 71 yrs. ± 8.89; tPSA 13.5 ng/ml ± 4.3) were analysed. Fourteen had a positive PET scan, which revealed 30 lesions. PCa was detected in 7/15 patients (46.7%) and four patients presented a clinically significant PCa: GS > 6. Over 58 cores, 25 (43.1%) were positive. No statistically significant difference in terms of mean and median values for SUVmax and SUVratio between benign and malignant lesions was found. PCa lesions with GS 3 + 3 (n = 3) showed a median SUVmax and SUVratio of 4.01 and 1.46, compared to 5.45 and 1.57, respectively for lesions with GS >6 (n = 4).

Conclusion

Software PET-CT/TRUS fusion-guided target biopsy could be a diagnostic alternative in patients with a suspected primary PCa and negative mpMRI, but its specificity appeared low.

PET and PET/CT with radiolabeled choline in prostate cancer: a critical reappraisal of 20 years of clinical studies

We here aim to provide a comprehensive and critical review of the literature concerning the clinical applications of positron emission tomography/computed tomography (PET/CT) with radiolabeled choline in patients with prostate cancer (PCa). We will initially briefly summarize the historical context that brought to the synthesis of [¹¹C]choline, which occurred exactly 20 years ago. We have arbitrarily grouped the clinical studies in three different periods, according to the year in which they were published and according to their relation with their applications in urology, radiotherapy and oncology. Studies at initial staging and, more extensively, studies in patients with biochemical failure, as well as factors predicting positive PET/CT will be reviewed. The capability of PET/CT with radiolabeled choline to provide prognostic information on PCa-specific survival will also be examined. The last sections will be devoted to the use of radiolabeled choline for monitoring the response to androgen deprivation therapy, radiotherapy, and chemotherapy. The accuracy and the limits of the technique will be discussed according to the information available from standard validation processes, including biopsy or histology. The clinical impact of the technique will be discussed on the basis of changes induced in the management of patients and in the evaluation of the response to therapy. Current indications to PET/CT, as officially endorsed by guidelines, or as routinely performed in the clinical practice will be illustrated. Emphasis will be made on methodological factors that might have influenced the results of the studies or their interpretation. Finally, we will briefly highlight the potential role of positron emission tomography/magnetic resonance and of new radiotracers for PCa imaging.

An Assessment of Early Response to Targeted Therapy via Molecular Imaging: A Pilot Study of 3'-deoxy-3'[(18)F]-Fluorothymidine Positron Emission Tomography 18F-FLT PET/CT in Prostate Adenocarcinoma

Fluorothymidine is a thymidine analog labeled with fluorine-18 fluorothymidine for positron emission tomography (¹⁸F-FLT-PET) imaging. Thymidine is a nucleic acid that is used to build DNA. Fluorine-18 fluorothymidine (¹⁸F-FLT) utilizes the same metabolic pathway as does thymidine but has a very low incidence of being incorporated into the DNA (<1%). ¹⁸F-FLT-PET could have a role in the evaluation of response to targeted therapy. We present here a pilot study where we investigated cellular metabolism and proliferation in patients with prostate cancer before and after targeted therapy. Seven patients with Stage IV prostate adenocarcinoma, candidates for targeted therapy inhibiting the hepatocyte growth factor/tyrosine-protein kinase Met (HGF/C-MET) pathway, were included in this study. The HGF/C-MET pathway is implicated in prostate cancer progression, and an evaluation of the inhibition of this pathway could be valuable. ¹⁸F-FLT was performed at baseline and within four weeks post-therapy. Tumor response was assessed semi-quantitatively and using visual response criteria. The range of SUVmax for ¹⁸F-FLT at baseline in the prostate varied from 2.5 to 4.2. This study demonstrated that ¹⁸F-FLT with positron emission tomography/computerized tomography (¹⁸F-FLT PET/CT) had only limited applications in the early response evaluation of prostate cancer. ¹⁸F-FLT PET/CT may have some utility in the assessment of response in lymph node disease. However, ¹⁸F-FLT PET/CT was not found to be useful in the evaluation of the prostate bed, metastatic skeletal disease, and liver disease.

Role of 18F-Choline PET/CT in guiding biopsy in patients with risen PSA levels and previous negative biopsy for prostate cancer

OBJECTIVES

To study ¹⁸F-Choline PET/CT in the diagnosis and biopsy guide of prostate cancer (pCa) in patients with persistently high prostate-specific antigen (PSA) and previous negative prostate biopsy. To compare the clinical risk factors and metabolic variables as predictors of malignancy.

METHODS

Patients with persistently elevated PSA in serum (total PSA >4ng/mL) and at least a previous negative or inconclusive biopsy were consecutively referred for a whole body ¹⁸F-Choline PET/CT. Patient age, PSA level, PSA doubling time (PSAdt) and PSA velocity (PSAvel) were obtained. PET images were visually (positive or negative) and semiquantitatively (SUVmax) reviewed. ¹⁸F-Choline uptake prostate patterns were defined as focal, multifocal, homogeneous or heterogeneous. Histology on biopsy using transrectal ultrasound-guided approach was the gold standard. Sensitivity (Se), specificity (Sp) and accuracy (Ac) of PET/CT for diagnosis of pCa were evaluated using per-patient and per-prostate lobe analysis. Receiver-operating-characteristic (ROC) curve analysis was used to assess the value of SUVmax to diagnose pCa. Correlation between PET/CT and biopsy results per-prostate lobe was assessed using the Chi-square test. Univariate and multivariate logistic regression analysis were applied to compare clinical risk factors and metabolic variables as predictors of malignancy.

RESULTS

Thirty-six out of 43 patients with histologic confirmation were included. In 11 (30.5%) patients, pCa was diagnosed (Gleason score from 4 to 9). The mean values of patient age, PSA level, PSAdt and PSAvel were: 65.5 years, 15.6ng/ml, 28.1 months and 8.5ng/mL per year, respectively. Thirty-three patients had a positive PET/CT; 18 had a focal pattern, 7 multifocal, 4 homogeneous and 4 heterogeneous. Se, Sp and Ac of PET/CT were of 100%, 12% and 38% in the patient based analysis, and 87%, 29% and 14% in the prostate lobe based analysis, respectively. The ROC curve analysis of SUVmax showed an AUC of 0.568 (p=0.52). On a lobe analysis, poor agreement was observed between PET/CT findings and biopsy results (p=0.097). In the univariate/multivariate analysis, none of clinical and metabolic variables were statistically significant as predictor of pCa.

CONCLUSION

Choline PET/CT is a suitable procedure for the detection of pCa in highly selected patients, however, a high rate of false positive should be expected.

Diagnostic value of integrated PET/MRI for detection and localization of prostate cancer: Comparative study of multiparametric MRI and PET/CT

PURPOSE

To evaluate the diagnostic value of integrated positron emission tomography/magnetic resonance imaging (PET/MRI) compared with conventional multiparametric MRI and PET/computed tomography (CT) for the detailed and accurate segmental detection/localization of prostate cancer.

MATERIALS AND METHODS

Thirty-one patients who underwent integrated PET/MRI using ¹⁸ F-choline and ¹⁸ F-FDG with an integrated PET/MRI scanner followed by radical prostatectomy were included. The prostate was divided into six segments (sextants) according to anatomical landmarks. Three radiologists noted the presence and location of cancer in each sextant on four different image interpretation modalities in consensus (1, multiparametric MRI; 2, integrated ¹⁸ F-FDG PET/MRI; 3, integrated ¹⁸ F-choline PET/MRI; and 4, combined interpretation of 1 and ¹⁸ F-FDG PET/CT). Sensitivity, specificity, accuracy, positive and negative predictive values, likelihood ratios, and diagnostic performance based on the DOR (diagnostic odds ratio) and NNM (number needed to misdiagnose) were evaluated for each interpretation modality, using the pathologic result as the reference standard. Detection rates of seminal vesicle invasion and extracapsular invasion were also evaluated.

RESULTS

Integrated ¹⁸ F-choline PET/MRI showed significantly higher sensitivity than did multiparametric MRI alone in high Gleason score patients (77.0% and 66.2%, P = 0.011), low Gleason score patients (66.7% and 47.4%, P = 0.007), and total patients (72.5% and 58.0%, P = 0.008) groups. Integrated ¹⁸ F-choline PET/MRI and ¹⁸ F-FDG PET/MRI showed similar sensitivity and specificity to combined interpretation of multiparametric MRI and ¹⁸ F-FDG PET/CT (for sensitivity, 58.0%, 63.4%, 72.5%, and 68.7%, respectively, and for specificity, 87.3%, 80.0%, 81.8%, 72.7%, respectively, in total patient group). However, integrated ¹⁸ F-choline PET/MRI showed the best diagnostic performance (as DOR, 11.875 in total patients, 27.941 in high Gleason score patients, 5.714 in low Gleason score groups) among the imaging modalities, regardless of Gleason score. Integrated ¹⁸ F-choline PET/MRI showed higher sensitivity and diagnostic performance than did integrated ¹⁸ F-FDG PET/MRI (as DOR, 6.917 in total patients, 15.143 in high Gleason score patients, 3.175 in low Gleason score groups) in all three patient groups.

CONCLUSION

Integrated PET/MRI carried out using a dedicated integrated PET/MRI scanner provides better sensitivity, accuracy, and diagnostic value for detection/localization of prostate cancer compared to multiparametric MRI. Generally, integrated ¹⁸ F-choline PET/MRI shows better sensitivity, accuracy, and diagnostic performance than does integrated ¹⁸ F-FDG PET/MRI as well as combined interpretation of multiparametric MRI with ¹⁸ F-FDG PET/CT.

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:597-609.

PET Imaging of Prostate Cancer Using Radiolabeled Choline

Although PET using fludeoxyglucose F 18 (FDG) is a promising modality for metabolic imaging of different tumors, the results in prostate cancer have been somewhat inconsistent. Low FDG avidity of most prostate cancer cells and urinary activity are suggested as the main limitations of FDG PET for the evaluation of prostate cancer. Prostate cancer exhibits increased choline metabolism, which is the rationale for using radiolabeled choline for PET. This article describes the basic concepts of radiolabeled choline regarding pharmacokinetics, radiation dosimetry, synthesis, and biodistribution, in addition to advances concerning clinical PET using 11C- and 18F-choline in primary staging and restaging of prostate cancer patients.

Positron emission tomography in imaging evaluation of staging, restaging, treatment response, and prognosis in prostate cancer

Prostate cancer is a prevalent public health problem worldwide. While imaging has played a major role in this disease, there still remain many challenges and opportunities. Positron emission tomography with various physiologically based radiotracers is fundamentally suited to interrogate this biologically and clinically heterogeneous disease along the course of its natural history. In this article, I review briefly the published evidence for the use of positron emission tomography with 18F-fluorodeoxyglucose, 11C-acetate, and 18F- or 11C-choline in the imaging evaluation of prostate cancer. Although the focus of the article will be on these radiotracers given the accumulated experience with them, but I will also comment on the outlook for the use of other emerging PET radiotracers such as those targeted to the prostate-specific membrane antigen and the amino acid metabolism pathway. It is anticipated that PET will play major role in the evaluation of prostate cancer in the current evidence-based medicine environment. There will also be exciting novel prospects for the use of therapeutic-diagnostic (theransotic) pairs in the management of patients with prostate cancer.

The Utility of Molecular Imaging in Prostate Cancer

Prostate cancer is the commonest solid-organ cancer diagnosed in males and represents an important source of morbidity and mortality worldwide. Imaging plays a crucial role in diagnosing prostate cancer and informs the ongoing management of the disease at all stages. Several novel molecular imaging technologies have been developed recently that have the potential to revolutionise disease diagnosis and the surveillance of patients living with prostate cancer. These innovations include hyperpolarised MRI, choline PET/CT and PSMA PET/CT. The major utility of choline and PSMA PET/CT currently lies in their sensitivity for detecting early recurrence after radical treatment for prostate cancer and identifying discrete lesions that may be amenable to salvage therapy. Molecular imaging is likely to play a future role in characterising genetic and biochemical signatures in individual tumours, which may be of particular significance as cancer therapies move into an era of precision medicine.

Increased choline uptake in macrophages and prostate cancer cells does not allow for differentiation between benign and malignant prostate pathologies

INTRODUCTION

Inflammatory cells may contribute to the choline uptake in different prostate pathologies. The aim of this study was (i) to assess if inflammatory cells incorporate choline and (ii) to potentially detect differences compared to FDG uptake. Therefore we investigated the uptake of [(3)H]choline and [(18)F]FDG in human prostate carcinoma cells and human inflammatory cells.

METHODS

Macrophages were cultured from isolated mononuclear cells, gained by density gradient centrifugation of human buffy coats. T-lymphocytes, B-lymphocytes and granulocytes were enriched by density gradient centrifugation before cell sorting by means of flow cytometry was performed. [(3)H]choline and [(18)F]FDG uptake of isolated inflammatory cells as well as of LNCaP and PC-3 human prostate carcinoma cells was assessed simultaneously in dual tracer uptake experiments.

RESULTS

Macrophages showed highest [(3)H]choline and [(18)F]FDG uptake compared to the tracer uptake rates of leukocytes. [(3)H]choline uptake of macrophages was in the same range as in prostate cancer cells. Lipopolysaccharide stimulation of macrophages resulted in an increase of [(18)F]FDG uptake in macrophages, but not in an increased [(3)H]choline uptake.

CONCLUSIONS

The high [(3)H]choline uptake in macrophages may be a source of false-positive PET results in diagnosis of prostate cancer by choline-PET/CT. As already known from FDG-PET, discrimination between tumor and inflammation in prostate cancer patients is not possible via choline-PET.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

The application of choline-PET for reliable primary prostate cancer detection and delineation has to be queried.

Imaging metabolic heterogeneity in cancer

As our knowledge of cancer metabolism has increased, it has become apparent that cancer metabolic processes are extremely heterogeneous. The reasons behind this heterogeneity include genetic diversity, the existence of multiple and redundant metabolic pathways, altered microenvironmental conditions, and so on. As a result, methods in the clinic and beyond have been developed in order to image and study tumor metabolism in the in vivo and in vitro regimes. Both regimes provide unique advantages and challenges, and may be used to provide a picture of tumor metabolic heterogeneity that is spatially and temporally comprehensive. Taken together, these methods may hold the key to appropriate cancer diagnoses and treatments in the future.

Index lesion characterization by (11)C-Choline PET/CT and Apparent Diffusion Coefficient parameters at 3 Tesla MRI in primary prostate carcinoma

BACKGROUND

Index lesion characterization is important in the evaluation of primary prostate carcinoma (PPC). The aim of this study was to analyze the contribution of (11) C-Choline PET/CT and the Apparent Diffusion Coefficient maps (ADC) in detecting the Index Lesion and clinically significant tumors in PPC.

METHODS

Twenty-one untreated patients with biopsy-proven PPC and candidates for radical prostatectomy (RP) were prospectively evaluated by means of Ultra-High Definition PET/CT and 3T MRI, which included T2-weighted imaging (T2WI) and ADC maps obtained from diffusion weighted imaging (DWI). Independent experts analyzed all the images separately and were unaware of the pathological data. In each case, the Index lesion was defined as the largest tumor measured on histopathology (Index H). In addition, the largest lesion observed on MRI (Index MRI) and the highest avid (11) C-Choline uptake lesion (Index PET) were obtained. The Gleason scores (GS) of the tumors were determined. PET/CT and ADC map quantitative parameters were also calculated. Measures of correlation among imaging parameters as well as the sensitivity (S), specificity (Sp), negative and positive predictive values (NPV and PPV) for tumor detection were analyzed. All data was validated with the pathological study.

RESULTS

In the morphological study, 139 foci of carcinoma were identified, 47 of which corresponded to clinically significant tumors (>0.5 cm(3)). The remaining foci presented a maximum diameter (dmax ) of 0.1 cm ± SD 0.75 and were not classified as clinically significant. Thirty-two tumors presented a GS (3 + 3), nine GS (3 + 4), and six GS (4 + 3). A total of 21 Index H (dmax = 1.37 cm SD ± 0.61) were identified. The S, Sp, NPV, and PPV for tumor detection with PET were 100%, 70%, 83%, 100%, and for MRI were 46%, 100%, 100%, 54%, respectively. Both Index PET and Index MRI were complementary and identified 95% of the Index H when quantitative criteria were used.

CONCLUSION

In spite of the fact that PET imaging has higher tumor sensitivity than MRI, (11) C-Choline PET and ADC maps have complementary roles in the evaluation of Index Lesion in PPC. Index PET and Index MRI could be complementary targets in the therapeutic planning of PPC.

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.

Initial prostate cancer diagnosis and disease staging--the role of choline-PET-CT

An early and correct diagnosis together with accurate staging of prostate cancer is necessary in order to plan the most appropriate treatment strategy. Morphological imaging modalities such as transrectal ultrasonography (TRUS), CT, and MRI can have some limitations regarding their accuracy for primary diagnosis and staging of prostate cancer; for instance, they have limited specificity in differentiating cancer from benign prostatic conditions and, by using size as the only criterion to characterize lymph node metastases, they might not be accurate enough for tumour characterization. In this scenario, PET-CT with (11)C-labelled or (18)F-labelled choline derivatives provides morphological and functional characterization and could overcome the limitations of the conventional imaging techniques. PET-CT is one of the most investigated molecular imaging modalities for prostate cancer diagnosis and staging. Currently, the main investigations on the role of PET-CT in the diagnosis and staging of prostate cancer have been performed on a retrospective basis and this type of analysis might be one of the main reasons why different results regarding its diagnostic accuracy have been reported.

Incidental abnormal FDG uptake in the prostate on 18-fluoro-2-deoxyglucose positron emission tomography-computed tomography scans

18-fluoro-2-deoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) scans are commonly used for the staging and restaging of various malignancies, such as head and neck, breast, colorectal and gynecological cancers. However, the value of FDG PET/CT for detecting prostate cancer is unknown. The aim of this study was to evaluate the clinical value of incidental prostate 18F-FDG uptake on PET/CT scans. We reviewed 18F-FDG PET/CT scan reports from September 2009 to September 2013, and selected cases that reported focal/diffuse FDG uptake in the prostate. We analyzed the correlation between 18F-FDG PET/CT scan findings and data collected during evaluations such as serum prostate-specific antigen (PSA) levels, digital rectal examination (DRE), transrectal ultrasound (TRUS), and/or biopsy to confirm prostate cancer. Of a total of 18,393 cases, 106 (0.6%) exhibited abnormal hypermetabolism in the prostate. Additional evaluations were performed in 66 patients. Serum PSA levels were not significantly correlated with maximum standardized uptake values (SUVmax) in all patients (rho 0.483, p=0.132). Prostate biopsies were performed in 15 patients, and prostate cancer was confirmed in 11. The median serum PSA level was 4.8 (0.55-7.06) ng/mL and 127.4 (1.06-495) ng/mL in the benign and prostate cancer groups, respectively. The median SUVmax was higher in the prostate cancer group (mean 10.1, range 3.8-24.5) than in the benign group (mean 4.3, range 3.1-8.8), but the difference was not statistically significant (p=0.078). There was no significant correlation between SUVmax and serum PSA, prostatic volume, or Gleason score. 18F-FDG PET/CT scans did not reliably differentiate malignant or benign from abnormal uptake lesions in the prostate, and routine prostate biopsy was not usually recommended in patients with abnormal FDG uptake. Nevertheless, patients with incidental prostate uptake on 18F-FDG PET/ CT scans should not be ignored and should be undergo further clinical evaluations, such as PSA and DRE.

Preclinical Evaluation of a Tailor-Made DOTA-Conjugated PSMA Inhibitor with Optimized Linker Moiety for Imaging and Endoradiotherapy of Prostate Cancer

Despite many advances in the past years, the treatment of metastatic prostate cancer still remains challenging. In recent years, prostate-specific membrane antigen (PSMA) inhibitors were intensively studied to develop low-molecular-weight ligands for imaging prostate cancer lesions by PET or SPECT. However, the endoradiotherapeutic use of these compounds requires optimization with regard to the radionuclide-chelating agent and the linker moiety between chelator and pharmacophore, which influence the overall pharmacokinetic properties of the resulting radioligand. In an effort to realize both detection and optimal treatment of prostate cancer, a tailor-made novel naphthyl-containing DOTA-conjugated PSMA inhibitor has been developed.

METHODS

The peptidomimetic structure was synthesized by solid-phase peptide chemistry and characterized using reversed-phase high-performance liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry. Subsequent (67/68)Ga and (177)Lu labeling resulted in radiochemical yields of greater than 97% or greater than 99%, respectively. Competitive binding and internalization experiments were performed using the PSMA-positive LNCaP cell line. The in vivo biodistribution and dynamic small-animal PET imaging studies were investigated in BALB/c nu/nu mice bearing LNCaP xenografts.

RESULTS

The chemically modified PSMA inhibitor PSMA-617 demonstrated high radiolytic stability for at least 72 h. A high inhibition potency (equilibrium dissociation constant [K(i)] = 2.34 ± 2.94 nM on LNCaP; K(i) = 0.37 ± 0.21 nM enzymatically determined) and highly efficient internalization into LNCaP cells were demonstrated. The small-animal PET measurements showed high tumor-to-background contrasts as early as 1 h after injection. Organ distribution revealed specific uptake in LNCaP tumors and in the kidneys 1 h after injection. With regard to therapeutic use, the compound exhibited a rapid clearance from the kidneys from 113.3 ± 24.4 at 1 h to 2.13 ± 1.36 percentage injected dose per gram at 24 h. The favorable pharmacokinetics of the molecule led to tumor-to-background ratios of 1,058 (tumor to blood) and 529 (tumor to muscle), respectively, 24 h after injection.

CONCLUSION

The tailor-made DOTA-conjugated PSMA inhibitor PSMA-617 presented here is sustainably refined and advanced with respect to its tumor-targeting and pharmacokinetic properties by systematic chemical modification of the linker region. Therefore, this radiotracer is suitable for a first-in-human theranostic application and may help to improve the clinical management of prostate cancer in the future.

Role for (11)C-choline PET in active surveillance of prostate cancer

INTRODUCTION

Active surveillance (AS) is an increasingly popular management strategy for men diagnosed with low-risk indolent prostate cancer. Current tests (prostate-specific antigen [PSA], clinical staging, and prostate biopsies) to monitor indolent disease lack accuracy. (11)C-choline positron emission tomography (PET) has excellent detection rates in local and distant recurrence of prostate cancer. We examine (11)C-choline PET for identifying aggressive prostate cancer warranting treatment in the AS setting.

METHODS

In total, 24 patients on AS had clinical assessment and PSA testing every 6 months and (11)C-choline PET and prostate biopsies annually. The sensitivity and specificity to identify prostate cancer and progressive disease (PD) were calculated for each (11)C-choline PET scan.

RESULTS

In total, 62 biopsy-paired, serial (11)C-choline PET scans were analyzed using a series of standard uptake value-maximum (SUVmax) cut-off thresholds. During follow-up (mean 25.3 months), 11 of the 24 low-risk prostate cancer patients developed PD and received definitive treatment. The prostate cancer detection rate with (11)C-choline PET had moderate sensitivity (72.1%), but low specificity (45.0%). PD prediction from baseline (11)C-choline PET had satisfactory sensitivity (81.8%), but low specificity (38.5%). The addition of clinical parameters to the baseline (11)C-choline PET improved specificity (69.2%), with a slight reduction in sensitivity (72.7%) for PD prediction.

CONCLUSIONS

Addition of (11)C-choline PET imaging during AS may help to identify aggressive disease earlier than traditional methods. However, (11)C-choline PET alone has low specificity due to overlap of SUV values with benign pathologies. Triaging low-risk prostate cancer patients into AS versus therapy will require further optimization of PET protocols or consideration of alternative strategies (i.e., magnetic resonance imaging, biomarkers).

Comparison between conventional imaging (abdominal-pelvic computed tomography and bone scan) and [(18)F]choline positron emission tomography/computed tomography imaging for the initial staging of patients with intermediate- tohigh-risk prostate cancer: A retrospective analysis

OBJECTIVE

The aim of this study was to evaluate the efficiency of [(18)F]fluorocholine positron emission tomography/computed tomography (FCH PET/CT) in detecting lymph-node and bone involvement in comparison with conventional imaging, such as abdominal-pelvic CT and bone scan, in the initial staging of prostate cancer (PCa).

MATERIALS AND METHODS

The study retrospectively evaluated 48 patients who had FCH PET/CT for the initial staging of PCa. At the same time, 32 of the 48 patients had a bone scan and 26 of the 48 patients had abdominal-pelvic diagnostic CT. Diagnostic performance of FCH PET/CT, i.e. sensitivity, specificity and accuracy, was evaluated on a per-patient basis for the whole population and then separately on a per-risk classification, and later in comparison with conventional imaging. Histological specimens or follow-up data were used as the standard of reference.

RESULTS

The overall accuracy of FCH PET/CT for lymph-node involvement was 83.3%. The sensitivity of FCH was higher in the high-risk subset (83.3%) than in the intermediate-risk group (33.3%), whereas FCH specificity was similar. In comparison with dedicated CT scan, FCH PET/CT showed a higher sensitivity and a similar specificity (46.2% vs 69.2% and 92.3% vs 92.3%, respectively). Moreover, the sensitivity and specificity of PET/CT were higher than those of bone scan (100% vs 90% and 86.4% vs 77.2%, respectively). In contrast with conventional imaging, PET/CT changed the staging of the PCa in 33.3% patients.

CONCLUSIONS

The efficiency of FCH PET/CT in detecting both bone and lymph-node involvement of PCa at initial staging was found to be higher than that of conventional imaging. Prospective clinical trials are needed to confirm these findings.

Management of urological malignancies: Has positron emission tomography/computed tomography made a difference?

Positron emission tomography/computed tomography (PET/CT) technology has been a significant, but expensive addition to the oncologist's armamentarium. The aim of this review was to determine the clinical utility of PET/CT in urological oncology, its impact on disease outcome and cost-effectiveness. We searched MedLine and peer reviewed journals for all relevant literature available online from the year 2000 until January 2014 regarding the use of PET/CT in the management of urological malignancies. (11)C-choline PET/CT has emerged as a powerful tool for assessment of biochemical relapse in prostate cancer. Use of novel radiotracers like (124)I-girentuximab has shown promise in the diagnosis of clear cell renal carcinoma. Fluorodeoxyglucose PET has a proven role in seminoma for the evaluation of postchemotherapy residual masses and has shown encouraging results when used for detection of metastasis in renal, bladder, and penile cancer. Introduction of novel radiotracers and advanced technology has led to a wider application of PET/CT in urological oncology. However, testicular seminoma aside, its impact on disease outcome and cost-effectiveness still needs to be established.

Imaging biomarkers in prostate cancer: role of PET/CT and MRI

Prostate-specific antigen (PSA) is currently the most widely used biomarker of prostate cancer (PCa). PSA suggests the presence of primary tumour and disease relapse after treatment, but it is not able to provide a clear distinction between locoregional and distant disease. Molecular and functional imaging, that are able to provide a detailed and comprehensive overview of PCa extension, are more reliable tools for primary tumour detection and disease extension assessment both in staging and restaging. In the present review we evaluate the role of PET/CT and MRI in the diagnosis, staging and restaging of PCa, and the use of these imaging modalities in prognosis, treatment planning and response assessment. Innovative imaging strategies including new radiotracers and hybrid scanners such as PET/MRI are also discussed.

Combined PET imaging and diffusion-weighted imaging of intermediate and high-risk primary prostate carcinomas with simultaneous [18F] choline PET/MRI

Purpose

To characterize intermediate and high-risk prostate carcinomas with measurements of standardized uptake values (SUVs) and apparent diffusion coefficient (ADC) values by means of simultaneous [¹⁸F] choline PET/MRI.

Materials and Methods

35 patients with primary prostate cancer underwent simultaneous [¹⁸F] choline PET/MRI. From these, 21 patients with an intermediate and high risk constellation who were not under ongoing hormonal therapy were included. Altogether 32 tumor lesions with a focal uptake of [¹⁸F] choline could be identified. Average ADC values (ADC_aver) minimum ADC values (ADC_min) as well as maximum and mean SUVs (SUV_max, SUV_mean) of tumor lesions were assessed with volume-of-interest (VOI) and Region-of-interest (ROI) measurements. As a reference, also ADC_aver, ADC_min and SUV_max and SUV_mean of non-tumorous prostate tissue were measured. Statistical analysis comprised calculation of descriptive parameters and calculation of Pearson’s product moment correlations between ADC values and SUVs of tumor lesions.

Results

Mean ADC_aver and ADC_min of tumor lesions were 0.94±0.22×10⁻³ mm²/s and 0.65±0.21×10⁻³ mm²/s, respectively. Mean SUV_max and SUV_mean of tumor lesions were 6.3±2.3 and 2.6±0.8, respectively. These values were in each case significantly different from the reference values (p<0.001). There was no significant correlation between the measured SUVs and ADC values (SUV_max vs. ADC_aver: R = −0.24, p = 0.179; SUV_max vs. ADC_min: R = −0.03, p = 0.877; SUV_mean vs. ADC_aver: R = −0.27, p = 0.136; SUV_mean vs. ADC_min: R = −0.08, p = 0.679).

Conclusion

Both SUVs and ADC values differ significantly between tumor lesions and healthy tissue. However, there is no significant correlation between these two parameters. This might be explained by the fact that SUVs and ADC values characterize different parts of tumor biology.

PET/CT imaging in cancer: current applications and future directions

Positron emission tomography (PET) is a radiotracer imaging method that yields quantitative images of regional in vivo biology and biochemistry. PET, now used in conjunction with computed tomography (CT) in PET/CT devices, has had its greatest impact to date on cancer and is now an important part of oncologic clinical practice and translational cancer research. In this review of current applications and future directions for PET/CT in cancer, the authors first highlight the basic principles of PET followed by a discussion of the biochemistry and current clinical applications of the most commonly used PET imaging agent, (18) F-fluorodeoxyglucose (FDG). Then, emerging methods for PET imaging of other biologic processes relevant to cancer are reviewed, including cellular proliferation, tumor hypoxia, apoptosis, amino acid and cell membrane metabolism, and imaging of tumor receptors and other tumor-specific gene products. The focus of the review is on methods in current clinical practice as well as those that have been translated to patients and are currently in clinical trials.

Imaging in prostate carcinoma

Imaging plays a central role in the detection, diagnosis, staging, and follow-up of prostate carcinoma. This article discusses the role of multiple imaging modalities in the diagnosis and staging of prostate cancer, with attention to imaging features of localized and metastatic disease, imaging adjuncts to improve prostate biopsy, and potential imaging biomarkers. In addition, the role of imaging in the management of prostate cancer, with emphasis on surveillance, evaluation of response to new therapies, and detection of recurrent disease is described. Lastly, future directions in prostate cancer imaging are presented.

Study of inter- and intra-observer reproducibility in the interpretation of [(18)F]choline PET/CT examinations in patients suffering from biochemically recurrent prostate cancer following curative treatment

Background

The aim of this study was to investigate the reproducibility of intra- and inter-observer interpretation of [¹⁸F]choline positron emission tomography/computed tomography examinations in patients suffering from biochemically recurrent prostate cancer following curative treatment.

Methods

A total of 60 patients with biochemical recurrence after curative treatment were included in this bicentric study. The interpretations were based on a systematic analysis of several anatomic regions and all the four nuclear medicine physicians used identical result consoles. The examinations were interpreted with no knowledge of the patients' clinical context. Two months later, a second interpretation of all these examinations was performed using the same method, in random order.

Results

To evaluate local recurrences, when the prostate is in place, the results showed moderate inter- and intra-observer reproducibility: concordance of all 4 physicians has a Fleiss' kappa coefficient of 0.553 with a confidence interval of (0.425 to 0.693). For patients who had had a prostatectomy, there was excellent concordance for the negative examinations. For the lymphatic basin, inter- and intra-observer reproducibility was excellent with a Fleiss' kappa coefficient of 0.892 with a confidence interval of (0.788 to 0.975). The lymphatic sub-group analysis was also good. For the lymphatic groups in the right or left hemi-pelves, all Fleiss' kappa and Cohen's kappa coefficients are varying from 0.760 to 1 with narrow confidence intervals from (0.536 to 0.984) to (1 to 1) in favour of good/excellent inter-observer reproducibility. To evaluate bone metastasis, inter-observer reproducibility was good with a Fleiss' kappa coefficient of 0.703 and a confidence interval of (0.407 to 0.881).

Conclusion

Our study is at time the only one on the reproducibility of interpretation of [¹⁸F]choline positron emission tomography/computed tomography examinations, which is a key examination for the treatment of patients suffering biochemical recurrence of prostate cancer. Interpretation of the [¹⁸F]choline positron emission tomography/computed tomography examination is not so useful at prostate level in patients not previously treated with prostatectomy but has a great interest on patients treated by prostatectomy. It showed good concordance in the interpretation of sub-diaphragmatic lymphatic recurrences as well as in bone metastasis.

3D prostate histology reconstruction: an evaluation of image-based and fiducial-based algorithms

PURPOSE

Evaluation of in vivo prostate imaging modalities for determining the spatial distribution and aggressiveness of prostate cancer ideally requires accurate registration of images to an accepted reference standard, such as histopathological examination of radical prostatectomy specimens. Three-dimensional (3D) reconstruction of prostate histology facilitates these registration-based evaluations by reintroducing 3D spatial information lost during histology processing. Because the reconstruction accuracy may constrain the clinical questions that can be answered with these data, it is important to assess the tradeoffs between minimally disruptive methods based on intrinsic image information and potentially more robust methods based on extrinsic fiducial markers.

METHODS

Ex vivo magnetic resonance (MR) images and digitized whole-mount histology images from 12 radical prostatectomy specimens were used to evaluate four 3D histology reconstruction algorithms. 3D reconstructions were computed by registering each histology image to the corresponding ex vivo MR image using one of two similarity metrics (mutual information or fiducial registration error) and one of two search domains (affine transformations or a constrained subset thereof). The algorithms were evaluated for accuracy using the mean target registration error (TRE) computed from homologous intrinsic point landmarks (3-16 per histology section; 232 total) identified on histology and MR images, and for the sensitivity of TRE to rotational, translational, and scaling initialization errors.

RESULTS

The algorithms using fiducial registration error and mutual information had mean ± standard deviation TREs of 0.7 ± 0.4 and 1.2 ± 0.7 mm, respectively, and one algorithm using fiducial registration error and affine transforms had negligible sensitivities to initialization errors. The postoptimization values of the mutual information-based metric showed evidence of errors due to both the optimizer and the similarity metric, and variation of parameters of the mutual information-based metric did not improve its performance.

CONCLUSIONS

The extrinsic fiducial-based algorithm had lower mean TRE and lower sensitivity to initialization than the intrinsic intensity-based algorithm using mutual information. A model relating statistical power to registration error for certain imaging validation study designs estimated that a reconstruction algorithm with a mean TRE of 0.7 mm would require 27% fewer subjects than the method used to initialize the algorithms (mean TRE 1.3 ± 0.7 mm), suggesting the choice of reconstruction technique can have a substantial impact on the design of imaging validation studies, and on their overall cost.

Evaluation of positron emission tomographic tracers for imaging of papillomavirus-induced tumors in rabbits

In this study, simultaneous positron emission tomography (PET)/magnetic resonance (MR) imaging was employed to evaluate the feasibility of the PET tracers 2-deoxy-2-18F-fluoro-d-glucose (18F-FDG), 11C-choline, and 18F-fluorothymidine (18F-FLT) to detect papillomavirus-induced tumors in an established rabbit model system. The combined PET/MR allowed the analysis of tracer uptake of the tumors using the morphologic information acquired by MR. New Zealand White rabbits were infected with cottontail rabbit papillomavirus genomes and were imaged for up to 10 months with a simultaneous PET/MR system during the course of infection. The uptake characteristics of the PET tracers 11C-choline and 18F-FLT of tumors and reference tissues were examined relative to the clinical standard, 18F-FDG. Tracer biodistribution of various organs was measured by gamma-counting after the last PET scan and compared to the in vivo PET/MR 18F-FDG uptake. Increased tracer uptake was found 2 months postinfection in primary tumors with 18F-FDG and 11C-choline, whereas 18F-FLT failed to detect the tumors at all measured time points. Our data show that the PET tracer 18F-FDG is superior for imaging papillomavirus-induced tumors in rabbits compared to 11C-choline and 18F-FLT. However, 11C-choline imaging, which has previously been applied to detect various tumor entities in patients, appears to be an alternative to 18F-FDG.

Advanced imaging for the early diagnosis of local recurrence prostate cancer after radical prostatectomy

Currently the diagnosis of local recurrence of prostate cancer (PCa) after radical prostatectomy (RT) is based on the onset of biochemical failure which is defined by two consecutive values of prostate-specific antigen (PSA) higher than 0.2 ng/mL. The aim of this paper was to review the current roles of advanced imaging in the detection of locoregional recurrence. A nonsystematic literature search using the Medline and Cochrane Library databases was performed up to November 2013. Bibliographies of retrieved and review articles were also examined. Only those articles reporting complete data with clinical relevance for the present review were selected. This review article is divided into two major parts: the first one considers the role of PET/CT in the restaging of PCa after RP; the second part is intended to provide the impact of multiparametric-MRI (mp-MRI) in the depiction of locoregional recurrence. Published data indicate an emerging role for mp-MRI in the depiction of locoregional recurrence, while the performance of PET/CT still remains unclear. Moreover Mp-MRI, thanks to functional techniques, allows to distinguish between residual glandular healthy tissue, scar/fibrotic tissue, granulation tissue, and tumour recurrence and it may also be able to assess the aggressiveness of nodule recurrence.

Fluorodeoxyglucose positron emission tomography may aid the diagnosis of aggressive primary prostate cancer: A case series study

Recent evidence has shown that positive results may be observed for fluorodeoxyglucose-positron emission tomography (FDG-PET) in undifferentiated, biologically aggressive and metastatic tumors. The present study describes a case series of six patients with normal prostate-specific antigen (PSA) serum levels who underwent FDG-PET due to other causes. Positive PET results were observed at the prostate and the patients were subsequently diagnosed with high-risk prostate cancer. Clinical, anamnestic, laboratory and instrumental data were collected from six asymptomatic patients with total serum PSA levels of <4 ng/ml who had undergone FDG-PET due to other causes. The FDG-PET and prostate biopsy were positive for prostate cancer. All the patients were treated with radical intent. The median age was 66 years (range, 52-72 years), the median total PSA value was 2.4 ng/ml (range, 1.5-3.9 ng/ml) and the body mass index was 26.4 (range, 21.8-30.2). Three of the six patients underwent FDG-PET due to a clinical suspicion of multiple myeloma, while three patients were examined for other oncological diseases. The pathological analysis at the prostate biopsy revealed three patients with a Gleason score of 6, two with a score of 7 (4+3) and one with a score of 8 (4+4). Five of the six patients were treated by radical prostatectomy and one by radiotherapy. The pathological analysis revealed one patient of pT2a stage, three of pT2c and one of pT3b. No patients demonstrated lymph node invasion. The definitive Gleason score was 3+3 in one patient, 4+3 in one patient, 4+4 in two patients and 5+3 in one patient. Following a median follow-up time of six months (range, 1-12 months), five of the six patients underwent FDG-PET again, which revealed negative results. At the end of this study, these patients were alive without evidence of disease. By contrast, one patient demonstrated positive FDG-PET results. In conclusion, FDG-PET has been used to characterize prostate cancers in patients with apparently normal PSA levels.

Correlation of metabolic tumor volume and 11C-choline uptake with the pathology of prostate cancer: evaluation by use of simultaneously recorded MR and PET images

PURPOSE

This study was conducted to assess the relationship between (11)C-choline uptake and pathologic findings obtained by combined use of magnetic resonance (MR) and positron emission tomography (PET) imaging of patients with prostate cancer.

MATERIALS AND METHODS

We retrospectively evaluated 69 patients with prostate cancer who underwent (11)C-choline PET-CT and magnetic resonance imaging before radical prostatectomy. Combined MR-PET images were acquired to obtain precise anatomic information. The maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) were compared with pathologic findings from resected specimens as the reference standard.

RESULTS

The mean and standard deviation of tumor SUVmax and MTV were 3.9 ± 1.8 and 12.9 ± 16.4, respectively. Tumors with high MTV (≧8.2) were more likely to be admixed with prostatic intraepithelial neoplasia (PIN) (p < 0.0001) or hyperplasia (p < 0.0001) in the background than those without these findings. Multiple regression analysis also revealed that the presence of hyperplasia (OR; 4.25, 95% CI 1.25-14.4, p = 0.02) and PIN (OR; 9.22, 95% CI 2.60-32.7, p = 0.001) were associated with tumors with high MTV.

CONCLUSION

We have demonstrated, by pathologic evaluation of patients with prostate cancer, that (11)C-choline uptake volume is greater for prostate cancer admixed with PIN and hyperplasia than that without.

Simultaneous 18F choline positron emission tomography/magnetic resonance imaging of the prostate: initial results

PURPOSE

The purposes of this study were to evaluate the feasibility of simultaneous 18F choline positron emission tomography (PET) and magnetic resonance imaging (MRI) of the prostate and to present the first clinical results of the method.

MATERIALS AND METHODS

From March 2012 to October 2012, a total of 15 consecutive patients were examined with simultaneous 18F choline PET/MRI. At the time of the examination, 8 patients had histologically proven prostate cancer, 2 patients had repeated prostate biopsies with negative results, and 5 patients had suspected prostate cancer with an elevated or rising prostate specific antigene level but did not have a prostate biopsy. Sequence protocol comprised T2-weighted high-resolution images and diffusion-weighted images of the prostate in addition to PET imaging. Image quality was assessed by 2 radiologists, and the PET images were evaluated qualitatively and quantitatively.

RESULTS

Simultaneous PET/MRI of the prostate was accomplished successfully in all patients. The method proved to be robust without technical failure, and the image quality was rated to be diagnostic in all examinations except in 1 diffusion-weighted imaging (DWI) data set that was judged to be nondiagnostic because of susceptibility artifacts. High-resolution T2-weighted images allowed exact correlation of elevated focal or diffuse choline uptake to suspicious T2-weighted lesions of the prostate. A high accordance was found between PET and DWI. However, PET-positive lesions were found in 3 patients wherein DWI did not indicate tumor in suspicious T2-weighted lesions.

CONCLUSIONS

Simultaneous positron emission tomography/magnetic resonance imaging of the prostate has the advantage of combining high-resolution prostate images, functional studies, and metabolic/molecular imaging. The PET component adds diagnostic confidence to the MRI-based parameters in identifying and localizing tumor in the prostate.

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.

Overview of randomized controlled treatment trials for clinically localized prostate cancer: implications for active surveillance and the United States preventative task force report on screening?

Prostate cancer and its management have been intensely debated for years. Recommendations range from ardent support for active screening and immediate treatment to resolute avoidance of screening and active surveillance. There is a growing body of level I evidence establishing a clear survival advantage for treatment of subsets of patients with clinically localized prostate cancer. This chapter presents a review of these randomized controlled trials. We argue that an understanding of this literature is relevant not only to those considering active surveillance but also to those evaluating the merits of screening. In addition, a number of important evidence-based conclusions concerning what should and should not be done can be gleaned from these trials.

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.

Choline PET/CT for imaging prostate cancer: an update

Whole-body positron emission tomography/computed tomography (PET/CT) with [(11)C]- and [(18)F]-labeled choline derivates has emerged as a promising molecular imaging modality for the evaluation of prostate cancer. (11)C- and (18)F-choline PET/CT are used successfully for restaging prostate cancer in patients with biochemical recurrence of disease after definitive therapy, especially when the serum prostate-specific antigen level is >1.0 ng/mL. (11)C- and (18)F-choline PET/CT have more limited roles for the initial staging of prostate cancer and for the detection of tiny lymph node metastases due to the low spatial resolution inherent to PET. Overall, these modalities are most useful in patients with a high pre-test suspicion of metastatic disease. The following is a review of the current clinical roles of (11)C- and (18)F-choline PET/CT in the management of prostate cancer.

The role of 11C-choline and 18F-fluorocholine positron emission tomography (PET) and PET/CT in prostate cancer: a systematic review and meta-analysis

CONTEXT

The role of positron emission tomography (PET) and PET/computed tomography (PET/CT) in prostate cancer (PCa) imaging is still debated, although guidelines for their use have emerged over the last few years.

OBJECTIVE

To systematically review and conduct a meta-analysis of the available evidence of PET and PET/CT using 11C-choline and 18F-fluorocholine as tracers in imaging PCa patients in staging and restaging settings.

EVIDENCE ACQUISITION

PubMed, Embase, and Web of Science (by citation of reference) were searched. Reference lists of review articles and included articles were checked to complement electronic searches.

EVIDENCE SYNTHESIS

In staging patients with proven but untreated PCa, the results of the meta-analysis on a per-patient basis (10 studies, n = 637) showed pooled sensitivity, specificity, and diagnostic odds ratio (DOR) of 84% (95% confidence interval [CI], 68-93%), 79% (95% CI, 53-93%), and 20.4 (95% CI, 9.9-42.0), respectively. The positive and negative likelihood ratios were 4.02 (95% CI, 1.73-9.31) and 0.20 (95% CI, 0.11-0.37), respectively. On a per-lesion basis (11 studies, n = 5117), these values were 66% (95% CI, 56-75%), 92% (95% CI, 78-97%), and 22.7 (95% CI, 8.9-58.0), respectively, for pooled sensitivity, specificity, and DOR; and 8.29 (95% CI, 3.05-22.54) and 0.36 (95% CI, 0.29-0.46), respectively, for positive and negative likelihood ratios. In restaging patients with biochemical failure after local treatment with curative intent, the meta-analysis results on a per-patient basis (12 studies, n = 1055) showed pooled sensitivity, specificity, and DOR of 85% (95% CI, 79-89%), 88% (95% CI, 73-95%), and 41.4 (95% CI, 19.7-86.8), respectively; the positive and negative likelihood ratios were 7.06 (95% CI, 3.06-16.27) and 0.17 (95% CI, 0.13-0.22), respectively.

CONCLUSIONS

PET and PET/CT imaging with 11C-choline and 18F-fluorocholine in restaging of patients with biochemical failure after local treatment for PCa might help guide further treatment decisions. In staging of patients with proven but untreated, high-risk PCa, there is limited but promising evidence warranting further studies. However, the current evidence shows crucial limitations in terms of its applicability in common clinical scenarios.

Role of choline PET/CT in guiding target volume delineation for irradiation of prostate cancer

Choline PET/CT has shown limitations for the detection of primary prostate cancer and nodal metastatic disease, mainly due to limited sensitivity and specificity. Conversely in the restaging of prostate cancer recurrence, choline PET/CT is a promising imaging modality for the detection of local regional and nodal recurrence with an impact on therapy management. This review highlights current literature on choline PET/CT for radiation treatment planning in primary and recurrent prostate cancer. Due to limited sensitivity and specificity in differentiating between benign and malignant prostatic tissues in primary prostate cancer, there is little enthusiasm for target volume delineation based on choline PET/CT. Irradiation planning for the treatment of single lymph node metastases on the basis of choline PET/CT is controversial due to its limited lesion-based sensitivity in primary nodal staging. In high-risk prostate cancer, choline PET/CT might diagnose lymph node metastases, which potentially can be included in the conventional irradiation field. Prior to radiation treatment of recurrent prostate cancer, choline PET/CT may prove useful for patient stratification by excluding distant disease which would require systemic therapy. In patients with local recurrence, choline PET/CT can be used to delineate local sites of recurrence within the prostatic resection bed allowing a boost to PET-positive sites. In patients with lymph node metastases outside the prostatic fossa and regional metastatic lymph nodes, choline PET/CT might influence radiation treatment planning by enabling extension of the target volume to lymphatic drainage sites with or without a boost to PET-positive lymph nodes. Further clinical randomized trials are required to assess treatment outcomes following choline-based biological radiation treatment planning in comparison with conventional radiation treatment planning.