Choline PET/CT for imaging prostate cancer: an update

Novel tracers to assess myocardial inflammation with radionuclide imaging

Myocardial inflammation plays a central role in the pathophysiology of various cardiac diseases. While FDG-PET is currently the primary method for molecular imaging of myocardial inflammation, its effectiveness is hindered by physiological myocardial uptake as well as its propensity for uptake by multiple disease-specific mechanisms. Novel radiotracers targeting diverse inflammatory immune cells and molecular pathways may provide unique insight through the visualization of underlying mechanisms central to the pathogenesis of inflammatory cardiac diseases, offering opportunities for increased understanding of immunocardiology. Moreover, the potentially enhanced specificity may lead to better quantification of disease activity, aiding in the guidance and monitoring of immunomodulatory therapy. This review aims to provide an update on advancements in non-FDG radiotracers for imaging myocardial inflammatory diseases, with a focus on cardiac sarcoidosis, myocarditis, and acute myocardial infarction.

Cancer of unknown primary eventually diagnosed as poorly differentiated prostate cancer: a case report

BACKGROUND

Prostate cancer has been well known to have a high prevalence among middle-aged and older men, with high incidence of metastases to the bone-the main metastatic site. However, prostate cancer among those less than 50 years of age is extremely rare, and neck swelling is seldom the initial symptom.

CASE PRESENTATION

We herein report case of a 47-year-old Japanese male with poorly differentiated prostate cancer that had been initially diagnosed as a cancer of unknown primary with multiple lymph node and bone metastases before reaching a definitive diagnosis. The patient has been started on endocrine therapy and is currently alive without progression.

DISCUSSION AND CONCLUSION

When locating the primary lesion in men with cancer of unknown primary, it is important to consider the possibility of prostate cancer, confirm serum prostate-specific antigen levels, and perform local prostate evaluation.

Validity of Anti-PSMA ScFvD2B as a Theranostic Tool: A Narrative-Focused Review

Prostate cancer (PCa) is the second leading cause of cancer among men, and its diagnosis and adequate staging are fundamental. Among the biomarkers identified in recent years for PCa management, prostate-specific-membrane-antigen (PSMA), physiologically expressed at a low level on healthy prostate and in other normal tissues and highly overexpressed in PCa, represents a reliable marker ideal for imaging and therapy. The development of anti-PSMA antibodies, such as D2B, demonstrated slow clearance of intact antibodies compared with fragments resulting in low tumor-to-blood ratios; however, the modular structural and functional nature of antibodies allowed the generation of smaller fragments, such as scFvs. In this review of the anti-PSMA antibody fragment scFvD2B, we combined further characterization of its biomolecular and tissue cross-reactivity characteristics with a comprehensive summary of what has already been performed in preclinical models to evaluate imaging and therapeutic activities. A molecular dynamics study was performed, and ScFvD2B occupied a limited conformational space, characterized by low-energy conformational basins, confirming the high stability of the protein structure. In the cross-reactivity study, the weak/absent immunoreactivity in non-tumor tissues was comparable to the PSMA expression reported in the literature. Biodistribution studies and therapeutic treatments were conducted in different animal models obtained by subcutaneous or locoregional injection of PSMA-positive-versus-negative xenografts. The maximum tumor uptake was observed for ¹²³I(SPECT), ¹²⁴I(PET), and optical imaging, which avoids kidney accumulation (compared with radiometals) and leads to an optimal tumor-to-kidney and tumor-to-background ratios. Regarding its possible use in therapy, experimental data suggested a strong and specific antitumor activity, in vitro and in vivo, obtained using CAR-T or NK-92/CAR cells expressing scFvD2B. Based on presented/reviewed data, we consider that scFvD2B, due to its versatility and robustness, seems to: (i) overcome some problems observed in other studied scFvs, very often relatively unstable and prone to form aggregates; (ii) have sufficient tumor-to-background ratios for targeting and imaging PSMA-expressing cancer; (iii) significantly redirect immune killing cells to PSMA-positive tumors when inserted in second-generation CAR-T or NK-92/CAR cells. These data suggest that our product can be considered the right reagent to fill the gap that still exists in PCa diagnosis and treatment.

Comparison of rigid and deformable coregistration between mpMRI and CT images in radiotherapy of prostate bed cancer recurrence

PURPOSE

To evaluate the accuracy of rigid coregistration between multiparametric magnetic resonance (mpMR) and computed tomography (CT) images for radiotherapy of prostate bed cancer recurrence.

MATERIALS AND METHOD

Fifty-three patients (59 nodules) accrued in a prospective study on salvage radiotherapy for prostatic bed recurrence were suitable for the analysis. Patients underwent a pre radiotherapy mpMR exam and a planning CT in the same treatment position and with control of organ filling. The site of recurrence was delineated on mpMR images and contours transferred on planning CT images using both rigid and deformable registrations. Coregistrations were evaluated by mathematical operators that quantify deformation (Jacobian determinant and vector curl) and similarity indices (Dice and Jaccard coefficients). Dose coverage was evaluated.

RESULTS

Deformable registration did not change volumes, (p = 0.92 MW test). The Jacobian coefficient and the vector curl revealed no important image deformations. Dice and Jaccard coefficients indicated dislocation of the nodule volumes. Dislocation magnitude was d = (5.6 ± 3.1) mm. Organ filling was not correlated with deformation or dislocation. Volumes were covered by the 95% isodose in 96% of cases when rigid registration was performed versus 75% of cases when deformed.

CONCLUSIONS

Rigid image coregistration is sufficiently accurate in this setting. The results indicate that the deformable registration tends to shrink the voxels and to dislocate the ROI, the adopted expansion for the recurrence volume adequately accounts for the observed deformation and dislocation, provided that organ filling is controlled.

A Prospective Study Assessing the Post-Prostatectomy Detection Rate of a Presumed Local Failure at mpMR with Either 64CuCl2 or 64CuPSMA PET/CT

Simple Summary

The role of PET/CT with two novel tracers was investigated in prostate cancer patients with both a biochemical failure after surgery and a presumed local failure at multiparametric MR. Overall, both PET tracers detected only about 50% of local failures. Therefore, multiparametric MR remains the exam of choice to investigate the prostatic fossa in patients who fail surgery.

Abstract

Background: We aimed assess the detection rate (DR) of positron emission tomography/computed tomography with two novel tracers in patients referred for salvage radiotherapy (sRT) with a presumed local recurrence at multiparametric magnetic resonance (mpMR) after radical prostatectomy (RP). Methods: The present prospective study was conducted at a single institution between August 2017 and June 2020. Eligibility criteria were undetectable PSA after RP; subsequent biochemical recurrence (two consecutive PSA rises to 0.2 ng/mL or greater); a presumed local failure at mpMR; no distant metastases at ¹⁸F-fluorocholine PET/CT (CH/PET); no previous history of androgen deprivation therapy. Patients were offered both ⁶⁴CuCl₂ PET/CT (CU/PET) and ⁶⁴Cu-PSMA PET/CT (PSMA/PET) before sRT. After image co-registration, PET findings were compared to mpMR ones in terms of DR and independent predictors of DR investigated at logistic regression. Results: A total of 62 patients with 72 nodules at mpMR were accrued. Compared to mpMR (DR = 100%, 95%CI: 94.9–100%), DRs were 47.2% (95%CI: 36.1–58.6%) and 54.4% (95%CI: 42.7–65.7%) for CU/PET and PSMA/PET, respectively (p < 0.001 for both). Both experimental PET/CT performed particularly poorly at PSA levels consistent with early sRT. Conclusions: The two novel radiotracers are inferior to mpMR in restaging the prostatic fossa for sRT planning purposes, particularly in the context of early salvage radiotherapy.

PSA and PSA Kinetics Thresholds for the Presence of 68Ga-PSMA-11 PET/CT-Detectable Lesions in Patients With Biochemical Recurrent Prostate Cancer

⁶⁸Ga-PSMA-11 positron-emission tomography/computed tomography (PET/CT) is commonly used for restaging recurrent prostate cancer (PC) in European clinical practice. The goal of this study is to determine the optimum time for performing these PET/CT scans in a large cohort of patients by identifying the prostate-specific-antigen (PSA) and PSA kinetics thresholds for detecting and localizing recurrent PC. This retrospective analysis includes 581 patients with biochemical recurrence (BC) by definition. The performance of ⁶⁸Ga-PSMA-11 PET/CT in relation to the PSA value at the scan time as well as PSA kinetics was assessed by the receiver-operating-characteristic-curve (ROC) generated by plotting sensitivity versus 1-specificity. Malignant prostatic lesions were identified in 77%. For patients that were treated with radical prostatectomy (RP) a PSA value of 1.24 ng/mL was found to be the optimal cutoff level for predicting positive and negative scans, while for patients previously treated with radiotherapy (RT) it was 5.75 ng/mL. In RP-patients with PSA value <1.24 ng/mL, 52% scans were positive, whereas patients with PSA ≥1.24 ng/mL had positive scan results in 87%. RT-patients with PSA <5.75 ng/mL had positive scans in 86% and for those with PSA ≥5.75 ng/mL 94% had positive scans. This study identifies the PSA and PSA kinetics threshold levels for the presence of ⁶⁸Ga-PSMA-11 PET/CT-detectable PC-lesions in BC patients.

Head-to-Head Comparison of 18F-Prostate-Specific Membrane Antigen-1007 and 18F-Fluorocholine PET/CT in Biochemically Relapsed Prostate Cancer

PURPOSE OF THE REPORT

The aim of the study was to prospectively compare performance of F-fluorocholine (FCH) and F-prostate-specific membrane antigen (PSMA)-1007 PET/CT in patients with biochemical relapse (BCR) of prostate cancer and low prostate-specific antigen levels.

METHODS

We prospectively enrolled 40 BCR patients after radical treatment and prostate-specific antigen levels 2.0 ng/mL or less. F-FCH and F-PSMA-1007 PET/CT imaging was performed within a mean interval of 54 ± 21 days. Scans were done 87 ± 10 and 95 ± 12 minutes after injecting 248 ± 35 and 295 ± 14 MBq of F-FCH and F-PSMA-1007, respectively. Rates of negative, equivocal, and positive scan results were compared per patient. Per lesion, findings were grouped as equivocal or highly suggestive of malignancy and then compared for their number, localization (local relapse, lymph nodes, bones), and SUVmax values.

RESULTS

Positive, equivocal, and negative results were reported in 60%, 27.5%, and 12.5% of F-PSMA-1007 and in 5%, 37.5%, and 57.5% of F-FCH scans, respectively. In 70% of scans, F-PSMA-1007 PET/CT upgraded F-FCH PET/CT results. F-PSMA-1007 scans also showed significantly more lesions (184 vs 63, P = 0.0006). Local relapse, lymph node, and bone lesions accounted, respectively, for 9%, 58%, and 33% of F-PSMA-1007 and 5%, 89%, and 6% F-FCH of PET/CT findings. Highly suspicious lesions accounted for 74% of F-PSMA-1007 and 11% of F-FCH PET/CT findings. In F-PSMA-1007 PET/CT SUVmax values of highly suggestive lesions were significantly higher than in equivocal lesions (median, 3.6 vs 2.5; P < 0.00001).

CONCLUSIONS

In early BCR patients F-PSMA-1007 showed a higher detection rate than F-FCH PET/CT. The former also showed more lesions in total, more highly suggestive lesions and less equivocal lesions.

The positivity rate of 68Gallium-PSMA-11 ligand PET/CT depends on the serum PSA-value in patients with biochemical recurrence of prostate cancer

Background: The aim of the present study is to analyze the efficacy of 68Gallium (Ga)-PSMA-11 PET/CT for detecting and localizing recurrent prostate carcinoma (PC) in patients with different prostate-specific antigen (PSA), PSA velocity (PSAvel) and doubling time (PSAdt).

Results: The PR of 68Ga-PSMA-11 PET/CT showed a positive relationship with PSA levels. Even at restaging PSA-values (PSAV) of lower than 0.2 ng/ml, PR was 41%. For PSAV of 0.2-<0.5 ng/ml the PR was 45%, 62% for PSAV of 0.5-<1.0 and 72% for PSAV of 1.0-<2.0 ng/ml. The PR increased to 85% for PSAV of 2.0-<5.0 and reached 94% at PSAV of ≥5.0 ng/ml. At PSA of <1 ng/ml/y the PR of PSAvel was 50% and increased to 98% at PSA >5 ng/ml/y. No significant association was found for PSAdt.

Methods: PET/CT scans of 660 patients with biochemical recurrence (BCR) after primary therapy of PC were included in the analysis. We correlated serum PSA levels, measured at the time of imaging with PSMA PET/CT-positivity rates (PR) as well as PSAvel (in 225 patients) and PSAdt (660 patients). Additionally we compared the incidence of localized disease to metastases as related to these PSA-biomarkers.

Conclusion: We have shown, in a large cohort of patients, that 68Ga-PSMA-11 PET/CT is a sensitive tool for restaging PC and has a high detection efficacy, even in patients with very low PSA levels (<0.2 ng/ml). Thus 68Ga-PSMA-11 PET/CT both identify and localize recurrent disease with implications for a more direct treatment approach (localized vs. systemic therapy).

Bone Scintigraphy in Staging of Newly Diagnosed Prostate Cancer in Regard of Different Risk Groups

Objectives

Prostate cancer (PC) is the most common cancer in men over 50 years of age. Bone scintigraphy is still performed in many institutions at the time of primary diagnosis. We aimed to evaluate the role of bone scan in the primary staging of PC in regard of different risk groups.

Methods

A retrospective analysis of bone scans in 296 patients (mean age 64±6 y) acquired at the time of primary diagnosis was performed in our institution. The median prostate specific antigen (PSA) was 6.73 ng/ml, all patients had a Gleason score of >5.

Results

Only 11/296 patients had a positive bone scan, 1 being in the intermediate risk group, 10 in the high-risk group and none in the low-risk group according to D'Amico classification.

Conclusion

Our results support the few published studies that less than 10% of patients with newly diagnosed PC by biopsy would develop bone metastasis, all in the intermediate or high-risk groups. Therefore, a staging by bone scan can only be recommended in patients with intermediate or high-risk, or symptomatic patients only.

Performance and Impact of Prostate Specific Membrane Antigen-Based Diagnostics in the Management of Men with Biochemical Recurrence of Prostate Cancer and its Role in Salvage Lymph Node Dissection

Up to 50% of patients initially treated for prostate cancer in a curative intent experience biochemical recurrence, possibly requiring adjuvant treatment. However, salvage treatment decisions, such as lymph node dissection or radiation therapy, are typically based on prostate specific antigen (PSA) recurrence. Importantly, common imaging modalities (e.g., computed tomography [CT], magnetic resonance imaging, and bone scan) are limited and the detection of recurrent disease is particularly challenging if PSA is low. Prostate specific membrane antigen (PSMA) positron-emission tomography/computed tomography (PET/CT) is a novel and promising imaging modality which aims to overcome the incapability of early identification of distant and regional metastases. Within this review, we summarize the current evidence related to PSMA-PET/CT in prostate cancer men diagnosed with biochemical recurrence after local treatment with curative intent. We discuss detection rates of PSMA-PET/CT stratified by PSA-levels and its impact on clinical decision making. Furthermore, we compare different image-fusion techniques such as PSMA-PET vs. F-/C-Choline-PET scans vs. PSMA-single photon emission computed tomography/CT. Finally, we touch upon the contemporary role of radio-guided-PSMA salvage lymphadenectomy.

Direct comparison of choline PET/CT and MRI in the diagnosis of lymph node metastases in patients with prostate cancer

BACKGROUND

Lymph node detection in prostate cancer is challenging and critical to determine treatment policy. Choline PET/CT (positron emission tomography/computed tomography) and magnetic resonance imaging (MRI) have been used for the evaluation of lymph node metastasis in patients with prostate cancer for the past decade. However, only limited patients underwent direct comparison studies.

PURPOSE

To evaluate the diagnostic performance of choline PET/CT compared with MRI imaging for detecting lymph node metastases in prostate cancer patients.

MATERIAL AND METHODS

Relevant English-language articles published before February 2018 were searched in PubMed database, Embase database, and Cochrane Library databases search using the keywords: (Prostate Neoplasm OR Prostate Cancer OR prostate carcinoma) and (Lymph Node) and (PET/CT OR positron emission tomography/computed tomography) and (choline or 2-hydroxy-N,N,N-trimethylethanaminium) and (magnetic resonance imaging OR MRI). Articles were included that directly compare the diagnostic performance and clinical utility of choline PET/CT and MRI for detecting lymph node metastases in prostate cancer patients. Study quality was assessed with QUADAS criteria. Analyses were performed on a per patient and a per node basis. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) were calculated using Meta-Disc 1.4 software. Summary receiver-operating characteristic (SROC) curves constructed.

RESULTS

A total of 362 patients from 8 studies involving fulfilled the inclusion criteria. On patient-based analysis, the pooled sensitivity, specificity, and DOR with a 95% confidence interval (CI) for choline PET/CT imaging were 0.59 (95%CI, 0.50-0.67), 0.92 (95%CI, 0.87-0.96), 17.37 (95%CI, 4.42-68.33), and for MRI imaging, they were 0.52 (95%CI, 0.44-0.61), 0.87 (95%CI, 0.81-0.92), 6.05 (95%CI, 3.09-11.85), respectively. On node-based, the corresponding values for choline PET/CT imaging were 0.51 (95%CI, 0.46-0.57), 0.99 (95%CI, 0.98-0.99), 65.55 (95%CI, 23.55-182.45), and for MRI imaging, they were 0.39 (95%CI, 0.34-0.44), 0.97 (95%CI, 0.96-0.97), 15.86 (95%CI, 8.96-28.05), respectively.

CONCLUSION

Choline PET/CT performed better than MRI imaging in evaluating the lymph nodes metastasis of prostate cancer patients and had the potential to be broadly applied in clinical practice.

Comparison of 11C-choline Positron Emission Tomography/Computed Tomography (PET/CT) and Conventional Imaging for Detection of Recurrent Prostate Cancer

We aimed to compare ¹¹C-choline positron emission tomography/computed tomography (PET/CT) with conventional imaging, including pelvic magnetic resonance imaging (MRI), contrast-enhanced chest, abdomen, and pelvic computed tomography (CT), and bone scintigraphy, for prostate cancer restaging. Thirty patients (median prostate-specific antigen [PSA: 11.8 ng/mL]) with suspected recurrent prostate cancer following definitive treatment underwent ¹¹C-choline PET/CT and conventional imaging, including pelvic MRI, contrast-enhanced chest, abdomen, and pelvic CT, and bone scintigraphy. The results were compared with regard to patient- and lesion-based diagnostic performance for local recurrence, and for lymph node and bony metastases using receiver operating characteristic (ROC) analysis and McNemar’s test. Documented local recurrence and node and bony metastases were present in 11 (36.7%), 10 (33.3%), and 17 (56.7%) cases, respectively, of the enrolled patients. Patient-based sensitivity / specificity / accuracy / area under the ROC curve for ¹¹C-choline-PET/CT for diagnosing local recurrence were 90.9% / 94.7% / 93.3% / 0.975 and for conventional imaging were 90.9% / 100% / 96.7% / 1.0. Those who underwent ¹¹C-choline-PET/CT for node metastasis were 90.0% / 95.0% / 93.3% / 0.925 and for conventional imaging were 70.0% / 95.0% / 86.7% / 0.905. Those who underwent ¹¹C-choline-PET/CT for bone metastasis were 94.1% / 92.3% / 93.3% / 0.991 and who underwent conventional imaging were 94.1% / 84.6% / 90.0% / 0.982. No significant differences were observed among them. The lesion-based detection rate of ¹¹C-choline PET/CT for local recurrences and node and bone metastases as compared to conventional imaging was 92.9% (13/14) vs. 92.9% (13/14); 87.1% (27/31) vs. 54.8% (17/31); and 96.9% (219/226) vs. 90.3% (204/226) respectively, with significant differences noted for detection of node and bone lesions (p=0.0044 and p=0.00030, respectively). ¹¹C-choline-PET/CT is more accurate in the detection of recurrent prostate cancer nodes and bony metastatic lesions compared to conventional imaging and has the advantage of restaging the disease in a single step.

18F-choline PET/MRI in suspected recurrence of prostate carcinoma

OBJECTIVE

To evaluate the usefulness of simultaneous ¹⁸F-choline PET/MRI in the suspicion of prostate cancer recurrence and to relate ¹⁸F-choline PET/MRI detection rate with analytical and pathological variables.

MATERIAL AND METHODS

27 patients with prostate cancer who received local therapy as primary treatment underwent a ¹⁸F-choline PET/MRI due to suspicion of recurrence (persistently rising serum PSA level). ¹⁸F-choline PET/MRI findings were validated by anatomopathological analysis, other imaging tests or by biochemical response to oncological treatment.

RESULTS

¹⁸F-choline PET/MRI detected disease in 15 of 27 patients (detection rate 55.56%). 4 (15%) presented exclusively local recurrence, 5 (18%) lymph node metastases and 7 (26%) bone metastases. Mean PSA (PSA_med) at study time was 2.94ng/mL (range 0.18-10ng/mL). PSA_med in patients with positive PET/MRI was 3.70ng/mL (range 0.24-10ng/mL), higher than in patients with negative PET/MRI, PSA_med 1.97ng/mL (range 0.18-4.38ng/mL), although without statistically significant differences. Gleason score at diagnosis in patients with a positive study was 7.33 (range 6-9) and in patients with a negative study was 7 (range 6-9), without statistically significant differences.

CONCLUSION

¹⁸F-choline PET/MRI detection rate was considerable despite the relatively low PSA values in our sample. The influence of Gleason score and PSA level on ¹⁸F-choline PET/MRI detection rate was not statistically significant.

Tiny Obturator Node Metastasis from Prostate Cancer Not Shown by FDG-PET/CT, CT, or MRI Detected by 11C-Choline PET/CT

We report a 65-year-old male with histopathologically proven prostate cancer and multiple pelvic node metastases using a robotic-assisted radical prostatectomy procedure plus extended pelvic lymph node dissection. Positron emission tomography (PET) scan findings demonstrated a moderate accumulation of ¹¹C-choline in a metastatic left obturator node sized 8 × 8 mm, though only a faint uptake of fluorodeoxyglucose (FDG) was noted. ¹¹C-choline PET/computed tomography (CT) may be useful for the diagnosis of a tiny metastatic lymph node not demonstrated by CT, magnetic resonance imaging, or FDG-PET/CT and to determine the need for an extended pelvic lymph node dissection.

Osteoblastic bone metastases from neuroendocrine tumor (NET) of unknown origin detected by 18fluorocholine PET/CT and its comparison with 68gallium-DOTATOC PET/CT: Case report and review of the literature

RATIONALE

Choline (CH) positron emission tomography (PET)/computed tomography (CT) with fluorine 18 (F) CH is increasingly used not only to evaluate patients with biochemically recurrent prostate cancer but also to assess metastatic lesions that are difficult or impossible to identify using more conventional modalities. Our experience with CH PET/CT has shown that it can also be used for many other malignancies.

PRESENTING CONCERNS

A 71-year-old male with a neuroendocrine tumor (NET) of unknown origin showed osteoblastic bone metastases positive to F-CH PET.

INTERVENTIONS

Diffuse bone and liver metastases were gallium-DOTATOC PET-positive with only mild uptake on FDG PET/CT. An increased prostate specific antigen (8 μg/L) gave rise to a suspicion of concurrent prostate cancer and the patient underwent F-CH PET/CT which showed diffuse uptake in the bone. A CT-guided bone biopsy confirmed osteoblastic bone metastases from NET.

OUTCOMES

Given the aggressiveness of the tumor, the patient underwent treatment with temozolomide from July 2015 to December 2015, maintaining stable disease. However, progression was documented in January 2016 and the patient was enrolled onto a phase II peptide receptor radionuclide therapy retreatment trial, which is currently ongoing.

MAIN LESSON

Our study highlights that NETs should be taken into consideration in the differential diagnosis of osteoblastic bone metastases showing F-CH uptake. A prognostic role for this imaging technique can also be hypothesized.

Development and Validation of a High-Pressure Liquid Chromatography Method for the Determination of Chemical Purity and Radiochemical Purity of a [68Ga]-Labeled Glu-Urea-Lys(Ahx)-HBED-CC (Positron Emission Tomography) Tracer

Background: Prostate-specific membrane antigen (PSMA) has gained high attention as a useful biomarker in the imaging evaluation of prostate cancer with positron emission tomography (PET) during recent years. [68Ga]-labeled Glu-urea-Lys(Ahx)-HBED-CC ([68Ga]-PSMA-HBED-CC) is a novel PSMA inhibitor radiotracer which has demonstrated its suitability in detecting prostate cancer. Preparation conditions may influence the quality and in vivo behavior of this tracer, and no standard procedure for the quality control (QC) is available. The aim of this study was to develop a new rapid and simple high-pressure liquid chromatography method of analysis for the routine QCs of [68Ga]-PSMA-HBED-CC to guarantee the high quality of the radiopharmaceutical product before release. Methods: A stepwise approach was used based on the quality by design concept of the International Conference of Harmonisation Q2 (R1) and Q8 (Pharmaceutical Development) guidelines in accordance with the regulations and requirements of European Association of Nuclear Medicine, Society of Nuclear Medicine, International Atomic Energy Agency, World Health Organization, and Italian Association of Nuclear Medicine and Molecular Imaging. The developed analytical test method was validated because a specific monograph in the pharmacopoeia is not available for [68Ga]-PSMA-HBED-CC. Results: The purity and quality of the radiopharmaceutical obtained according to the proposed method resulted high enough to safely administrate it to patients. An excellent linearity was found between 0.8 and 5 μg/mL, with a detection limit of 0.2 μg/mL. Assay imprecision (% CV) was <2%. Conclusions: The developed method to assess the radiochemical and chemical purity of [68Ga]-PSMA-HBED-CC is rapid, accurate, and reproducible, allowing routinely the use of this PET tracer as a diagnostic tool for imaging prostate cancer and also assuring patient safety.

Targeting personalized medicine in a non-Hodgkin lymphoma patient with 18F-FDG and 18F-choline PET/CT

Early diagnosis and staging of non-Hodgkin lymphoma (NHL) is essential for therapeutic strategy decision. Positron emission tomography/computed tomography (PET/CT) with fluordeoxyglucose (FDG), a glucose analogue, labeled with fluor-18 (18F-FDG) has been used to evaluate staging, therapy response and prognosis in NHL patients. However, in some cases, 18F-FDG has shown false-positive uptake due to inflammatory reaction after chemo and/or radiation therapy. In this case report, we present a NHL patient evaluated with 18F-FDG and 18F-choline PET/CT scan imaging pre- and post-therapy. 18F-FDG and 18F-choline PET/CT were performed for the purpose of tumor staging and have shown intense uptake in infiltrative tissue as well as in the lymph node, but with some mismatching in the tumor. Post-treatment 18F-FDG and 18F-choline PET/ CT scans revealed no signs of radiotracer uptake, suggesting complete remission of the tumor. 18F-choline may be a complimentary tool for staging and assessment of therapeutic response in non-Hodgkin lymphoma, while non-18F-FDG tracer can be used for targeted therapy and patient management.

Does Choline PET/CT Change the Management of Prostate Cancer Patients With Biochemical Failure?

PURPOSE

The FDA approved C-11 choline PET/computed tomography (CT) for imaging patients with recurrent prostate cancer in 2012. Subsequently, the 2014 NCCN guidelines have introduced labeled choline PET/CT in the imaging algorithm of patients with suspected recurrent disease. However, there is only scarce data on the impact of labeled choline PET/CT findings on disease management. We hypothesized that labeled-choline PET/CT studies showing local or regional recurrence or distant metastases will have a direct role in selection of appropriate patient management and improve radiation planning in patients with disease that can be controlled using this mode of therapy.

METHODS

This retrospective study was approved by the Tel Aviv Sourasky and Sheba Medical Center's Helsinki ethical review committees. Patient characteristics including age, PSA, stage, prior treatments, and pre-PET choline treatment recommendations based on NCCN guidelines were recorded. Patients with biochemical failure and without evidence of recurrence on physical examination or standard imaging were offered the option of additional imaging with labeled choline PET/CT. Treatment recommendations post-PET/CT were compared with pre-PET/CT ones. Pathologic confirmation was obtained before prostate retreatment. A nonparametric χ test was used to compare the initial and final treatment recommendations following choline PET/CT.

RESULTS

Between June 2010 and January 2014, 34 labeled-choline PET/CT studies were performed on 33 patients with biochemical failure following radical prostatectomy (RP) (n=6), radiation therapy (RT) (n=6), brachytherapy (n=2), RP+salvage prostate fossa RT (n=14), and RP+salvage prostate fossa/lymph node RT (n=6). Median PSA level before imaging was 2 ng/mL (range, 0.16 to 79). Labeled choline PET/CT showed prostate, prostate fossa, or pelvic lymph node increased uptake in 17 studies, remote metastatic disease in 9 studies, and failed to identify the cause for biochemical failure in 7 scans.PET/CT altered treatment approach in 18 of 33 (55%) patients (P=0.05). Sixteen of 27 patients (59%) treated previously with radiation were retreated with RT and delayed or eliminated androgen deprivation therapy: 1 received salvage brachytherapy, 10 received salvage pelvic lymph node or prostate fossa irradiation, 2 brachytherapy failures received salvage prostate and lymph nodes IMRT, and 3 with solitary bone metastasis were treated with radiosurgery. Eleven of 16 patients retreated responded to salvage therapy with a significant PSA response (<0.2 ng/mL), 2 patients had partial biochemical responses, and 3 patients failed. The median duration of response was 500±447 days. Two of 6 patients with no prior RT were referred for salvage prostatic fossa RT: 1 received dose escalation for disease identified in the prostate fossa and another had inclusion of "hot" pelvic lymph nodes in the treatment volume.

CONCLUSIONS

These early results suggest that labeled choline PET/CT imaging performed according to current NCCN guidelines may change management and improve care in prostate cancer patients with biochemical failure by identifying patients for referral for salvage radiation therapy, improving radiation planning, and delaying or avoiding use of androgen deprivation therapy.

PSMA ligands in prostate cancer - Probe optimization and theranostic applications

Due to its selective overexpression in prostate cancer (PCa), the prostate-specific membrane antigen (PSMA) has been recognized as a highly promising target for diagnostic and therapeutic applications. So far, various PSMA ligands have been developed for radiolabeling with radioisotopes such as ⁶⁸Ga or ¹⁸F which can be used for specific visualization and diagnosis of PSMA-expressing PCa. In addition, PSMA ligands suitable for radiolabeling with ¹³¹I or ¹⁷⁷Lu have become available to the clinics, allowing PSMA-based radioligand therapies. Here, we provide a comprehensive review of the most frequently used PSMA ligands, their structural modifications, and the impact of those on clinical applications.

Integrated 68Ga-HBED-CC-PSMA-PET/MRI in patients with suspected recurrent prostate cancer

AIM

Evaluate the diagnostic accuracy of ⁶⁸Ga-labeled HBED-CC-PSMA-PET/MRI for detection of recurrent PCa in comparison to PET/CT.

METHODS

48 patients with suspected recurrent PCa underwent PET/CT after injection of the ⁶⁸Ga-HBED-CC-PSMA ligand followed by integrated PET/MRI. Image analysis was performed by nuclear medicine physicians and radiologists with respect to the detection of lymph node metastases, bone metastases and local recurrence of the tumour. Image quality was evaluated visually based on a three-point ordinal scale.

RESULTS

From 48 patients initially examined, 25 were finally eligible for qualitative and quantitative image evaluation. In 14 patients, neither PET/CT nor PET/MRI found tumour lesions, and 9 patients were excluded from image analysis due to a pronounced extinction artifact around the urinary bladder (halo). In comparison to ⁶⁸Ga-HBED-CC-PSMA-PET/CT, ⁶⁸Ga-HBED-CC-PSMA-PET/MRI identified 14 vs. 9 local recurrences in the prostate bed and 23 vs. 20 PET-positive lymph nodes, and 4 vs. 4 PET-positive bone lesions, respectively. While the improved detection of suspicious lymph nodes was primarily attributable to the PET component, the advantageous detection of tumour recurrences in the prostate bed was chiefly referable to the superior soft-tissue contrast of the MR component of integrated PET/MRI. Analysis of SUV_max revealed that ⁶⁸Ga-HBED-CC-PSMA-PET/MRI provided significantly higher SUV_max compared to ⁶⁸Ga-HBED-CC-PSMA-PET/CT (17.6, range 2.0-49.6, and 15.1, range 3.5-36.8, respectively, p = 0.0019).

CONCLUSION

⁶⁸Ga-HBED-CC-PSMA-PET/MRI was found to be superior as compared to ⁶⁸Ga-HBED-CC-PSMA-PET/CT in the detection of PSMA-expressing prostate bed recurrences.

11C-Choline-Avid but 18F-FDG-Nonavid Prostate Cancer with Lymph Node Metastases on Positron Emission Tomography

Choline is a new positron emission tomography (PET) tracer useful for detection of prostate cancer and metastatic lesions. We report a 70-year-old man with prostate cancer and multiple abdominal, pelvic, and inguinal node metastases. PET scans demonstrated accumulation of ¹¹C-choline in the primary tumor and lymph node metastases but no accumulation of ¹⁸F-FDG. Choline PET/computed tomography may be useful for diagnosis of advanced prostate cancer with suspected metastatic lesions and treatment planning.

Whole-body diffusion-weighted magnetic resonance imaging (WB-DW-MRI) vs choline-positron emission tomography-computed tomography (choline-PET/CT) for selecting treatments in recurrent prostate cancer

OBJECTIVE

To determine the effectiveness of whole-body diffusion-weighted magnetic resonance imaging (WB-DW-MRI) in detecting metastases by comparing the results with those from choline-positron emission tomography-computed tomography (choline-PET/CT) in patients with biochemical relapse after primary treatment, and no metastases in bone scintigraphy, CT and/or pelvic MRI, or metastatic/oligometastatic prostate cancer (PCa). Patients with this disease profile who could benefit from treatment with stereotactic body radiation therapy (SBRT) were selected and their responses to these techniques were rated.

MATERIALS AND METHODS

This was a prospective, controlled, unicentric study, involving 46 consecutive patients from our centre who presented biochemical relapse after adjuvant, salvage or radical treatment with external beam radiotherapy, or brachytherapy. After initial tests (bone scintigraphy, CT, pelvic MRI), 35 patients with oligometastases or without them were selected. 11 patients with multiple metastases were excluded from the study. WB-DW-MRI and choline-PET/CT was then performed on each patient within 1 week. The results were interpreted by specialists in nuclear medicine and MRI. If they were candidates for treatment with ablative SBRT (SABR), they were then evaluated every three months with both tests.

RESULTS

Choline-PET/CT detected lesions in 16 patients that were not observable using WB-DW-MRI. The results were consistent in seven patients and in three cases, a lesion was observed using WB-DW-MRI that was not detected with choline-PET/CT. The Kappa value obtained was 0.133 (p = 0.089); the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of WB-DW-MRI were estimated at 44.93, 64.29, 86.11, and 19.15%, respectively. For choline-PET/CT patients, the sensitivity, specificity, PPV, and NPV were 97.10, 58.33, 93.06, and 77.78%, respectively.

CONCLUSIONS

Choline-PET/CT has a high global sensitivity while WB-DW-MRI has a high specificity, and so they are complementary techniques. Future studies with more enrolled patients and a longer follow-up period will be required to confirm these data. The initial data show that the best technique for evaluating response after SBRT is choline-PET/CT. Trial registration number NCT02858128.

Optimization of Acquisition time of 68Ga-PSMA-Ligand PET/MRI in Patients with Local and Metastatic Prostate Cancer

Objective

The aim of this optimization study was to minimize the acquisition time of ⁶⁸Ga-HBED-CC-PSMA positron emission tomography/magnetic resonance imaging (PET/MRI) in patients with local and metastatic prostate cancer (PCa) to obtain a sufficient image quality and quantification accuracy without any appreciable loss.

Methods

Twenty patients with PCa were administered intravenously with the ⁶⁸Ga-HBED-CC-PSMA ligand (mean activity 99 MBq/patient, range 76–148 MBq) and subsequently underwent PET/MRI at, on average, 168 min (range 77–320 min) after injection. PET and MR imaging data were acquired simultaneously. PET acquisition was performed in list mode and PET images were reconstructed at different time intervals (1, 2, 4, 6, 8, and 10 min). Data were analyzed regarding radiotracer uptake in tumors and muscle tissue and PET image quality. Tumor uptake was quantified in terms of the maximum and mean standardized uptake value (SUV_max, SUV_mean) within a spherical volume of interest (VOI). Reference VOIs were drawn in the gluteus maximus muscle on the right side. PET image quality was evaluated by experienced nuclear physicians/radiologists using a five-point ordinal scale from 5–1 (excellent—insufficient).

Results

Lesion detectability linearly increased with increasing acquisition times, reaching its maximum at PET acquisition times of 4 min. At this image acquisition time, tumor lesions in 19/20 (95%) patients were detected. PET image quality showed a positive correlation with increasing acquisition time, reaching a plateau at 4–6 min image acquisition. Both SUV_max and SUV_mean correlated inversely with acquisition time and reached a plateau at acquisition times after 4 min.

Conclusion

In the applied image acquisition settings, the optimal acquisition time of ⁶⁸Ga-PSMA-ligand PET/MRI in patients with local and metastatic PCa was identified to be 4 min per bed position. At this acquisition time, PET image quality and lesion detectability reach a maximum while SUV_max and SUV_mean do not change significantly beyond this time point.

Update on advances in molecular PET in urological oncology

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)F-FDG) has emerged as a powerful tool for the combined metabolic and anatomic evaluation of many cancers. In urological oncology, however, the use of (18)F-FDG has been limited by a generally low tumor uptake, and physiological excretion of FDG through the urinary system. (18)F-FDG PET/CT is useful when applied to specific indications in selected patients with urological malignancy. New radiotracers and positron emission tomography/magnetic resonance imaging (PET/MRI) are expected to further improve the performance of PET in uro-oncology.

Value of bimodal (18)F-choline-PET/MRI and trimodal (18)F-choline-PET/MRI/TRUS for the assessment of prostate cancer recurrence after radiation therapy and radical prostatectomy

Between 27% and 53% of all patients who undergo radical prostatectomy (RP) or radiation therapy (RT) as the first-line treatment of prostate cancer (PCa) develop a biochemical recurrence. Imaging plays a pivotal role in restaging by helping to distinguish between local relapse and metastatic disease (i.e., lymph-node and skeletal metastases). At present, the most promising tools for assessing PCa patients with biochemical recurrence are multiparametric magnetic resonance imaging (mpMRI) and positron emission tomography (PET)/computed tomography (CT) with radio-labeled choline derivatives. The main advantage of mpMRI is its high diagnostic accuracy in detecting local recurrence, while choline-PET/CT is able to identify lymph-node metastases when they are not suspicious on morphological imaging. The most recent advances in the field of fusion imaging have shown that multimodal co-registration, synchronized navigation, and combined interpretation are more valuable than the individual; separate assessment offered by different diagnostic techniques. The objective of the present essay was to describe the value of bimodal choline-PET/mpMRI fusion imaging and trimodal choline-PET/mpMRI/transrectal ultrasound (TRUS) in the assessment of PCa recurrence after RP and RT. Bimodal choline-PET/mpMRI fusion imaging allows morphological, functional, and metabolic information to be combined, thereby overcoming the limitations of each separate imaging modality. In addition, trimodal real-time choline-PET/mpMRI/TRUS fusion imaging may be useful for the planning and real-time guidance of biopsy procedures in order to obtain histological confirmation of the local recurrence.

Preclinical and first clinical experience with the gastrin-releasing peptide receptor-antagonist [⁶⁸Ga]SB3 and PET/CT

PURPOSE

Gastrin-releasing peptide receptors (GRPR) represent attractive targets for tumor diagnosis and therapy because of their overexpression in major human cancers. Internalizing GRPR agonists were initially proposed for prolonged lesion retention, but a shift of paradigm to GRPR antagonists has recently been made. Surprisingly, radioantagonists, such as [(99m)Tc]DB1 ((99m)Tc-N4'-DPhe(6),Leu-NHEt(13)]BBN(6-13)), displayed better pharmacokinetics than radioagonists, in addition to their higher inherent biosafety. We introduce here [(68)Ga]SB3, a [(99m)Tc]DB1 mimic-carrying, instead of the (99m)Tc-binding tetraamine, the chelator DOTA for labeling with the PET radiometal (68)Ga.

METHODS

Competition binding assays of SB3 and [(nat)Ga]SB3 were conducted against [(125)I-Tyr(4)]BBN in PC-3 cell membranes. Blood samples collected 5 min postinjection (pi) of the [(67)Ga]SB3 surrogate in mice were analyzed using high-performance liquid chromatography (HPLC) for degradation products. Likewise, biodistribution was performed after injection of [(67)Ga]SB3 (37 kBq, 100 μL, 10 pmol peptide) in severe combined immunodeficiency (SCID) mice bearing PC-3 xenografts. Eventually, [(68)Ga]SB3 (283 ± 91 MBq, 23 ± 7 nmol) was injected into 17 patients with breast (8) and prostate (9) cancer. All patients had disseminated disease and had received previous therapies. PET/CT fusion images were acquired 60-115 min pi.

RESULTS

SB3 and [(nat)Ga]SB3 bound to the human GRPR with high affinity (IC50: 4.6 ± 0.5 nM and 1.5 ± 0.3 nM, respectively). [(67)Ga]SB3 displayed good in vivo stability (>85 % intact at 5 min pi). [(67)Ga]SB3 showed high, GRPR-specific and prolonged retention in PC-3 xenografts (33.1 ± 3.9%ID/g at 1 h pi - 27.0 ± 0.9%ID/g at 24 h pi), but much faster clearance from the GRPR-rich pancreas (≈160%ID/g at 1 h pi to <17%ID/g at 24 h pi) in mice. In patients, [(68)Ga]SB3 elicited no adverse effects and clearly visualized cancer lesions. Thus, 4 out of 8 (50 %) breast cancer and 5 out of 9 (55 %) prostate cancer patients showed pathological uptake on PET/CT with [(68)Ga]SB3.

CONCLUSION

[(67)Ga]SB3 showed excellent pharmacokinetics in PC-3 tumor-bearing mice, while [(68)Ga]SB3 PET/CT visualized lesions in about 50 % of patients with advanced and metastasized prostate and breast cancer. We expect imaging with [(68)Ga]SB3 to be superior in patients with primary breast or prostate cancer.

PSMA Ligands for Radionuclide Imaging and Therapy of Prostate Cancer: Clinical Status

Prostate cancer (PCa) is the most common malignancy in men worldwide, leading to substantial morbidity and mortality. At present, imaging of PCa has become increasingly important for staging, restaging, and treatment selection. Until recently, choline-based positron emission tomography/computed tomography (PET/CT) represented the state-of-the-art radionuclide imaging technique for these purposes. However, its application is limited to patients with high PSA levels and Gleason scores. Prostate-specific membrane antigen (PSMA) is a promising new target for specific imaging of PCa, because it is upregulated in the majority of PCa. Moreover, PSMA can serve as a target for therapeutic applications. Currently, several small-molecule PSMA ligands with excellent in vivo tumor targeting characteristics are being investigated for their potential in theranostic applications in PCa. Here, a review of the recent developments in PSMA-based diagnostic imaging and therapy in patients with PCa with radiolabeled PSMA ligands is provided.

Pretargeted immunoPET of prostate cancer with an anti-TROP-2 x anti-HSG bispecific antibody in mice with PC3 xenografts

PURPOSE

Pretargeting with bispecific antibodies and radiolabeled hapten-peptides could be used to specifically target tumors with high target-to-background ratios. TF12 is a trivalent bispecific antibody that consists of two anti-TROP-2 Fab fragments and one anti-HSG (histamine-succinyl-glycine) Fab fragment. The TROP-2 antigen is expressed in many epithelial cancers, including prostate cancer (PC), and therefore, this bispecific antibody can be used for pretargeting of PC. In this study, the potential for pretargeted radioimmunoPET with TF12 and the (68)Ga-labeled di-HSG peptide IMP288 in mice with human PC xenografts was investigated using 2-deoxy-2-[(18)F]fluoro-D-glucose ([(18)F]FDG) as a reference.

PROCEDURES

The potential of pretargeted immunoPET with TF12 and the (68)Ga-labeled di-HSG hapten-peptide, IMP288, was studied in mice with subcutaneous PC3 tumors using [(18)F]FDG as a reference. Furthermore, the use of this pretargeting system for imaging PC lesions was evaluated in mice with intraperitoneally growing tumors with [(18)F]FDG as a reference.

RESULTS

[(68)Ga]lMP288 showed rapid accumulation in the TF12 pretargeted subcutaneous tumor (7.2 ± 1.1 % ID/g) with low uptake in the kidneys (1.8 ± 0.5 % ID/g) and high tumor-to-blood ratios (17.4 ± 11.2) at 1 h p.i. Accumulation of [(18)F]FDG in the s.c. tumors was significantly lower (3.4 ± 0.9 % ID/g, P = 0.008), with lower tumor-to-blood ratios (3.0 ± 1.9, P = 0.011). ImmunoPET/CT images clearly visualized both subcutaneous and intraperitoneal tumors as small as 5 mm(3) with low blood levels and kidney uptake as early as 1 h p.i.

CONCLUSION

Pretargeted immunoPET with TF12 in combination with a (68)Ga-labeled hapten-peptide is an efficient system for rapid, sensitive, and specific imaging of prostate cancer.

The clinical role of multimodality imaging in the detection of prostate cancer recurrence after radical prostatectomy and radiation therapy: past, present, and future

Detection of the recurrence sites in prostate cancer (PCa) patients affected by biochemical recurrence after radical prostatectomy (RP) and radiation therapy (RT) is still a challenge for clinicians, nuclear medicine physicians, and radiologists. In the era of personalised and precision care, this task requires the integration, amalgamation, and combined analysis of clinical and imaging data from multiple sources. At present, multiparametric Magnetic Resonance Imaging (mpMRI) and choline–positron emission tomography (PET) are giving encouraging results; their combination allows the effective detection of local, lymph nodal, and skeletal recurrences at low PSA levels. Future diagnostic perspectives include the clinical implementation of PET/MRI scanners, multimodal fusion imaging platforms for retrospective co-registration of PET and MR images, real-time transrectal ultrasound/mpMRI fusion imaging, and novel organ-specific PET radiotracers.

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.

FDG-PET/CT for pre-operative staging and prognostic stratification of patients with high-grade prostate cancer at biopsy

Background

The role of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in prostate cancer (PCa) has not been well defined yet. Because high-grade PCa tends to exhibit increased glycolytic rate, FDG-PET/CT could be useful in this setting. The aim of this study was to assess the value of FDG-PET/CT for pre-operative staging and prognostic stratification of patients with high-grade PCa at biopsy.

Methods

Fifty-four patients with a Gleason sum ≥8 PCa at biopsy underwent FDG-PET/CT as part of the staging workup. Thirty-nine patients underwent radical prostatectomy (RP) and pelvic lymph node (LN) dissection, 2 underwent LN dissection only, and 13 underwent non-surgical treatments. FDG-PET/CT findings from clinical reports, blinded reading and quantitative analysis were correlated with clinico-pathological characteristics at RP.

Results

Suspicious foci of increased FDG uptake were found in the prostate, LNs and bones in 44, 13 and 6% of patients, respectively. Higher clinical stage, post-RP Gleason sum and pattern, and percentage of cancer involvement within the prostate were significantly associated with the presence of intraprostatic FDG uptake (IPFU) (P < 0.05 in all cases). Patients without IPFU who underwent RP were downgraded to Gleason ≤7 in 84.6% of cases, as compared to 30.8% when IPFU was reported (P = 0.003). Qualitative and quantitative IPFU were significantly positively correlated with post-RP Gleason pattern and sum, and pathological T stage. Absence and presence of IPFU were associated with a median 5-year cancer-free survival probability of 70.2 and 26.9% (P = 0.0097), respectively, using the CAPRA-S prognostic tool.

Conclusion

These results suggest that, among patients with a high-grade PCa at biopsy, FDG-PET/CT could improve pre-treatment prognostic stratification by predicting primary PCa pathological grade and survival probability following RP.

Biomarkers in preclinical cancer imaging

In view of the trend towards personalized treatment strategies for (cancer) patients, there is an increasing need to noninvasively determine individual patient characteristics. Such information enables physicians to administer to patients accurate therapy with appropriate timing. For the noninvasive visualization of disease-related features, imaging biomarkers are expected to play a crucial role. Next to the chemical development of imaging probes, this requires preclinical studies in animal tumour models. These studies provide proof-of-concept of imaging biomarkers and help determine the pharmacokinetics and target specificity of relevant imaging probes, features that provide the fundamentals for translation to the clinic. In this review we describe biological processes derived from the “hallmarks of cancer” that may serve as imaging biomarkers for diagnostic, prognostic and treatment response monitoring that are currently being studied in the preclinical setting. A number of these biomarkers are also being used for the initial preclinical assessment of new intervention strategies. Uniquely, noninvasive imaging approaches allow longitudinal assessment of changes in biological processes, providing information on the safety, pharmacokinetic profiles and target specificity of new drugs, and on the antitumour effectiveness of therapeutic interventions. Preclinical biomarker imaging can help guide translation to optimize clinical biomarker imaging and personalize (combination) therapies.

Magnetic resonance imaging diagnosis of metastatic lymph nodes in a rabbit model: efficacy of PJY10, a new ultrasmall superparamagnetic iron oxide agent, with monodisperse iron oxide core and multiple-interaction ligands

Background

Accurate diagnosis of lymph node metastasis is crucial in treatment planning for cancer patients. Despite the use of various parameters, making correct diagnosis of a small metastatic or a hyperplastic benign node is still a challenge. In this study, we evaluated the feasibility of detecting lymph node metastasis using a new ultrasmall superparamagnetic iron oxide particle, PJY10, in a rabbit model.

Methods

To make metastatic and benign lymph nodes, either VX2 carcinoma or fecal material suspension was inoculated into thighs of 56 rabbits three weeks or three days before magnetic resonance (MR) imaging, respectively. T2*-weighted 3T MR imaging was performed before and 24 hours after PJY10 injection (5.2 [n = 15], 7.8 [n = 17], and 10.4 [n = 24] mg Fe/kg). MR images were correlated with pathologic results to calculate sensitivity and specificity. Quantitative analysis of the signal intensity (SI) – number of voxels_[low] (the fraction of the number of voxels with the normalized SI on the postcontrast image lower than that on the precontrast image) and mean SI ratio – was also performed for each lymph node.

Results

Sensitivities were 100% at all three dosages, whereas specificity increased with increasing dosage (89% at 10.4 mg Fe/kg). The benign nodes had a significantly higher number of voxels_[low] and a lower mean SI ratio than the metastatic nodes at the dosage of 10.4 mg Fe/kg (P<.001). Az values were 0.905 for the number of voxels_[low] and 0.952 for the mean SI ratio. The number of voxels_[low] (P = .019) and the mean SI ratio (P = .034) had significant correlations with the histopathologic area ratio of metastatic foci in the metastatic nodes at 10.4 mg Fe/kg.

Conclusions

PJY10 enabled clear demonstration of lymph node metastasis with high sensitivity and specificity at its optimal dosage of 10.4 mg Fe/kg.

An Incidental Finding of Mucinous Colon Cancer by (18)F-Choline PET/CT Determining a Change in Clinical Management of a Patient with Recurrent Prostate Adenocarcinoma

A 66-year-old-man underwent a PET/CT scan after a biochemical relapse for a prostate cancer previously treated with a laparoscopic surgical procedure which revealed a focal uptake in the posterior wall of sigmoid colon. The biopsy demonstrated a colon cancer with mucinous differentiation producing a shift in clinical priority. To the best of our knowledge this is the first report in the English literature describing the detection by ¹⁸F-choline PET/CT of a colorectal cancer with mucinous differentiation.

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.