Long-term follow-up of 111In-capromab pendetide (ProstaScint) scan as pretreatment assessment in patients who undergo salvage radiotherapy for rising prostate-specific antigen after radical prostatectomy for prostate cancer

Development and Characterization of 99mTc-scFvD2B as a Potential Radiopharmaceutical for SPECT Imaging of Prostate Cancer

Previously, we demonstrated that the 177Lu-labeled single-chain variable fragment of an anti-prostate-specific membrane antigen (PSMA) IgG D2B antibody (scFvD2B) showed higher prostate cancer (PCa) cell uptake and tumor radiation doses compared to 177Lu-labeled Glu-ureide-based PSMA inhibitory peptides. To obtain a 99mTc-/177Lu-scFvD2B theranostic pair, this research aimed to synthesize and biochemically characterize a novel 99mTc-scFvD2B radiotracer. The scFvD2B-Tag and scFvD2B antibody fragments were produced and purified. Then, two HYNIC derivatives, HYNIC-Gly-Gly-Cys-NH2 (HYNIC-GGC) and succinimidyl-HYNIC (S-HYNIC), were used to conjugate the scFvD2B-Tag and scFvD2B isoforms, respectively. Subsequently, chemical characterization, immunoreactivity tests (affinity and specificity), radiochemical purity tests, stability tests in human serum, cellular uptake and internalization in LNCaP(+), PC3-PIP(++) or PC3(-) PCa cells of the resulting unlabeled HYNIC-scFvD2B conjugates (HscFv) and 99mTc-HscFv agents were performed. The results showed that incorporating HYNIC as a chelator did not affect the affinity, specificity or stability of scFvD2B. After purification, the radiochemical purity of 99mTc-HscFv radiotracers was greater than 95%. A two-sample t-test of 99mTc-HscFv1 and 99mTc-HscFv1 uptake in PC3-PIP vs. PC3 showed a p-value < 0.001, indicating that the PSMA receptor interaction of 99mTc-HscFv agents was statistically significantly higher in PSMA-positive cells than in the negative controls. In conclusion, the results of this research warrant further preclinical studies to determine whether the in vivo pharmacokinetics and tumor uptake of 99mTc-HscFv still offer sufficient advantages over HYNIC-conjugated peptides to be considered for SPECT/PSMA imaging.

Targeted Radiation and Immune Therapies-Advances and Opportunities for the Treatment of Prostate Cancer

Prostate cancer is the most diagnosed malignancy in men in the United States and the second leading cause of cancer-related death. For localized disease, radiation therapy is a standard treatment that is often curative. For metastatic disease, radiation therapy has been primarily used for palliation, however, several newer systemic radiation therapies have been demonstrated to significantly improve patient outcomes and improve survival. In particular, several targeted radionuclide therapies have been approved for the treatment of advanced-stage cancer, including strontium-89, samarium-153, and radium-223 for bone-metastatic disease, and lutetium-177-labeled PSMA-617 for patients with prostate-specific membrane antigen (PSMA)-expressing metastatic castration-resistant prostate cancer (mCRPC). Contrarily, immune-based treatments have generally demonstrated little activity in advanced prostate cancer, with the exception of the autologous cellular vaccine, sipuleucel-T. This has been attributed to the presence of an immune-suppressive prostate cancer microenvironment. The ability of radiation therapy to not only eradicate tumor cells but also potentially other immune-regulatory cells within the tumor immune microenvironment suggests that targeted radionuclide therapies may be well poised to combine with immune-targeted therapies to eliminate prostate cancer metastases more effectively. This review provides an overview of the recent advances of targeted radiation agents currently approved for prostate cancer, and those being investigated in combination with immunotherapy, and discusses the challenges as well as the opportunities in this field.

Molecular and metabolic imaging of castration-resistant prostate cancer: state of art and future prospects

Prostate cancer (PCa) represents the most common tumor in male and one of the most relevant causes of death in Western countries. Androgen deprivation therapy (ADT) constitutes a widely used approach in advanced PCa. When PCa progresses in spite of ADT and castrate levels of testosterone, the severe clinical condition termed as metastatic castration-resistant prostate cancer (mCRPC) takes place. The only approach to mCRPC has been represented by chemotherapy with taxanes for many years. Nevertheless, recently introduced treatments such as 2nd generation antiandrogens (i.e. enzalutamide and abiraterone), cell immunotherapy with sipuleucel-T or targeted alpha therapy with 223Ra-dichloride, have dramatically changed mCRPC prognosis. These novel therapies call for an unmet need for imaging biomarkers suitable for patients' pre-treatment stratification and response assessment. In this scenario, nuclear medicine can provide several metabolic and molecular probes for investigating pathological processes at a cellular and sub-cellular level. The aim of this paper is to review the most relevant findings of the literature published to date on this topic, giving particular emphasis to the pros and cons of each tracer and also covering future prospects for defining personalized therapeutic approaches.

Synthesis and Evaluation of 99mTc-Tricabonyl Labeled Isonitrile Conjugates for Prostate-Specific Membrane Antigen (PSMA) Image

Prostate-specific membrane antigen (PSMA) is a biomarker expressed on the surface of prostate cancer (PCa). In an effort to improve the detection and treatment of PCa, small urea-based PSMA inhibitors have been studied extensively. In the present study, we aimed to develop 99mTc-tricabonyl labeled urea-based PSMA conjugates containing isonitrile (CN-R)-coordinating ligands ([99mTc]Tc-15 and [99mTc]Tc-16). Both the PSMA conjugates were obtained at high radiochemical efficiency (≥98.5%). High in vitro binding affinity was observed for [99mTc]Tc-15 and [99mTc]Tc-16 (Kd = 5.5 and 0.2 nM, respectively) in PSMA-expressing 22Rv1 cells. Tumor xenografts were conducted using 22Rv1 cells and rapid accumulation of [99mTc]Tc-16 (1.87 ± 0.11% ID/g) was observed at 1 h post-injection, which subsequently increased to (2.83 ± 0.26% ID/g) at 4 h post-injection. However, [99mTc]Tc-15 showed moderate tumor uptake (1.48 ± 0.18% ID/g), which decreased at 4 h post-injection (0.81 ± 0.09% ID/g). [99mTc]Tc-16 was excreted from non-targeted tissues with high tumor-to-blood (17:1) and tumor-to-muscle ratio (41:1) at 4 h post-injection at approximately 4 times higher levels than [99mTc]Tc-15. Uptakes of [99mTc]Tc-15 and [99mTc]Tc-16 to PSMA-expressing tumor and tissues were significantly blocked by co-injection of 2-(Phosphonomethyl)-pentandioic acid (2-PMPA), suggesting that their uptakes are mediated by PSMA specifically. Whole-body single photon emission computed tomography imaging of [99mTc]Tc-16 verified the ex vivo biodistribution results and demonstrated clear visualization of tumors and tissues expressing PSMA compared to [99mTc]Tc-15. In conclusion, using [99mTc]Tc-16 rather than [99mTc]Tc-15 may be the preferable because of its relatively high tumor uptake and retention.

99mTc-labeling and evaluation of a HYNIC modified small-molecular inhibitor of prostate-specific membrane antigen

INTRODUCTION

Prostate-specific membrane antigen (PSMA) is a well-established target in the development of radiopharmaceuticals for the diagnosis and therapy of prostate cancer (PCa). In this study, we evaluated a novel ^99mTc-labeled small molecular inhibitor of PSMA.

METHODS

This new small-molecular inhibitor of PSMA, 6-hydrazinonicotinate-Aminocaproic acid-Lysine-Urea-Glutamate (HYNIC-ALUG) was radiolabeled by ^99mTc and was evaluated both in vitro and in vivo using PCa models (PC-3 and LNCaP). Radiation dosimetry was assessed in mice.

RESULTS

^99mTc-HYNIC-ALUG showed excellent stability in different media. A cell assay preliminarily displayed its specificity for PSMA. The inhibitor showed good pharmacokinetics making it suitable for in vivo imaging. PC-3-derived tumors showed no obvious radioactive uptake; however, the LNCaP-derived tumors showed very high radioactive uptake which was significantly decreased by the selective PSMA inhibitor 2-PMPA. Biodistribution in LNCaP xenografts showed an optimum tumor-to-blood ratio of 24.23±3.54 at 2h. Tumor uptake was also decreased in the inhibition experiment with 2-PMPA (19.45±2.14%ID/g versus 1.42±0.15%ID/g at 2h). The effective dose of the ^99mTc-HYNIC-ALUG was 8.4E-04mSv/MBq.

CONCLUSIONS

A new ^99mTc-labeled PSMA inhibitor with specific accumulation in PSMA-positive tumors and low background in other organs was synthesized. The radiopharmaceutical also showed very low radiation dosimetry. This agent may significantly improve the diagnosis, staging, and subsequent monitoring of therapeutic effects in PCa patients.

A paradigm shift from anatomic to functional and molecular imaging in the detection of recurrent prostate cancer

Approximately a third of men with localized prostate cancer who are treated with external beam radiation therapy (EBRT) or radical prostatectomy (RP) develop biochemical failure (BF). Presumably, BF will progress to distant metastasis and prostate cancer-specific mortality in some patients over subsequent years. Accurate detection of recurrent disease is important because it allows for appropriate treatment selection (e.g., local vs systemic therapy) and early delivery of therapy (e.g., salvage EBRT), which affect patient outcome. In this article, we discuss the paradigm shift in imaging technology in the detection of recurrent prostate cancer. First, we discuss the commonly used morphological and anatomical imaging modalities and their role in the post-RP and post-EBRT settings of BF. Second, we discuss the accuracy of functional and molecular imaging techniques, many of which are under investigation. Further studies are needed to establish the role of imaging techniques for detection of cancer recurrence and clinical decision-making.

Meeting the challenges of PET-based molecular imaging in cancer

As personalized medicine becomes a reality, there is a need for specific imaging agents that reflect molecular characteristics of a cancer. Fluorodeoxyglucose is an important advance because of its sensitivity. Newer molecular imaging probes offer higher specificity and are categorized as: radiolabeled biomimetics; antibody-antibody fragments and drug-drug-like compounds. Biomimetics have high sensitivity but tend to be less specific as they often engage natural transporters and metabolic pathways. Antibodies and their fragments are specific but may be limited by slow clearance. Labeled drugs and drug-like compounds offer good specificity but may be limited in sensitivity. There are numerous challenges facing molecular imaging related to their complexity. Additionally, fear of ionizing radiation and regulatory constraints have somewhat inhibited clinical translation. However, there is reason for optimism due to economies of scale and a changing health care system, which places a premium on diagnostic accuracy. Although molecular imaging is not likely to become mainstream in the near future, its long-term prospects for doing so are excellent.

Glutamate carboxypeptidase II in diagnosis and treatment of neurologic disorders and prostate cancer

Glutamate carboxypeptidase II (GCPII) is a membrane-bound binuclear zinc metallopeptidase with the highest expression levels found in the nervous and prostatic tissue. Throughout the nervous system, glia-bound GCPII is intimately involved in the neuron-neuron and neuron-glia signaling via the hydrolysis of N-acetylaspartylglutamate (NAAG), the most abundant mammalian peptidic neurotransmitter. The inhibition of the GCPII-controlled NAAG catabolism has been shown to attenuate neurotoxicity associated with enhanced glutamate transmission and GCPII-specific inhibitors demonstrate efficacy in multiple preclinical models including traumatic brain injury, stroke, neuropathic and inflammatory pain, amyotrophic lateral sclerosis, and schizophrenia. The second major area of pharmacological interventions targeting GCPII focuses on prostate carcinoma; GCPII expression levels are highly increased in androgen-independent and metastatic disease. Consequently, the enzyme serves as a potential target for imaging and therapy. This review offers a summary of GCPII structure, physiological functions in healthy tissues, and its association with various pathologies. The review also outlines the development of GCPII-specific small-molecule compounds and their use in preclinical and clinical settings.

Management of prostate cancer patients with lymph node involvement: a rapidly evolving paradigm

Although widespread PSA screening has inevitably led to increased diagnosis of lower risk prostate cancer, the number of patients with nodal involvement at baseline remains high (nearly 40% of high risk patients initially staged cN0). These rates probably do not reflect the true incidence of prostate cancer with lymph node involvement among patients selected for external beam radiotherapy (EBRT), as patients selected for surgery often have more favorable prognostic features. At many institutions, radical treatment directed only at the prostate is considered standard and patients known to have regional disease are often managed palliatively with androgen deprivation therapy (ADT) for presumed systemic disease. New imaging tools such as MR lymphangiography, choline-based PET imaging or combined SPECT/CT now allow surgeons and radiation oncologists to identify and target nodal metastasis and/or lymph nodes with a high risk of occult involvement. Recent advances in the field of surgery including the advent of extended nodal dissection and sentinel node procedures have suggested that cancer-specific survival might be improved for lymph-node positive patients with a low burden of nodal involvement when managed with aggressive interventions. These new imaging tools can provide radiation oncologists with maps to guide delivery of high dose conformal radiation to a target volume while minimizing radiation toxicity to non-target normal tissue. This review highlights advances in imaging and reports how they may help to define a new paradigm to manage node-positive prostate cancer patients with a curative-intent.

A phosphoramidate-based prostate-specific membrane antigen-targeted SPECT agent

BACKGROUND

Prostate-specific membrane antigen (PSMA) remains an active target for imaging and therapeutic applications for prostate cancer.

METHODS

In the present study, an irreversible phosphoramidate inhibitor, CTT-54 (IC50 = 14 nM), has been modified to deliver 99mTc-(CO)3-DTPA as a SPECT imaging payload to PSMA+ cells in vivo and in vitro. Percent uptake, competitive binding, and internalization will evaluate the imaging agent in vitro. Preliminary biodistribution and imaging will be utilized for in vivo evaluation.

RESULTS

In vitro studies demonstrate that the radiotracer 99mTc-(CO)3-DTPA-CTT-54 exhibits increasing cellular uptake in the PSMA+ LNCaP cells over time. More importantly, it was found that 99mTc-(CO)3-DTPA-CTT-54 is rapidly internalized into LNCaP cells, presumably through the PSMA enzyme-inhibitor complex. In a pilot biodistribution study, increasing accumulation of the radiotracer in LNCaP xenografts was observed from 2 to 4 hr and significant clearance from non-target tissues.

CONCLUSIONS

While DTPA may not represent the ideal chelate structure for 99mTc(CO)3, the data provides proof-of-concept support for the development of a next-generation phosphoramidate-based PSMA inhibitor-conjugates for use as SPECT imaging agents.

ACR Appropriateness Criteria® posttreatment follow-up of prostate cancer

Although prostate cancer can be effectively treated, recurrent or residual disease after therapy is not uncommon and is usually detected by a rise in prostate-specific antigen. Patients with biochemical prostate-specific antigen relapse should undergo a prompt search for the presence of local recurrence or distant metastatic disease, each requiring different forms of therapy. Various imaging modalities and image-guided procedures may be used in the evaluation of these patients. Literature on the indications and usefulness of these radiologic studies and procedures in specific clinical settings is reviewed. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Diagnostic performance of In-111 capromab pendetide SPECT/CT in localized and metastatic prostate cancer

PURPOSE

To determine the diagnostic performance of In-111 capromab pendetide single photon emission computed tomography/computed tomography (SPECT/CT), in the prostate gland, seminal vesicles, and lymph nodes via correlation to a gold standard of histopathology.

MATERIALS AND METHODS

In this study, we retrospectively reviewed all In-111 capromab pendetide SPECT/CT acquired at our institution for dedicated histopathology within a 4-month period. Statistical measures of performance were calculated in terms of glandular, seminal vesicle, and lymph node activity. The accuracies of glandular and seminal vesicle activity were then correlated to the indices of risk, including the stage, Gleason score, and prostate-specific antigen level, as well as the treatment history.

RESULTS

Of the 200 scans meeting the criteria of our study, 197 had prostate gland histopathology, 94 had bilateral seminal vesicle histopathology, and 5 had a total of 43 resected lymph nodes for comparison. The overall accuracies of the scan results were determined to be 77.7% (area under the receiver operating characteristic curve [AUC] = 0.539) for the gland, 67.0% (AUC = 0.510) for the seminal vesicles, and 93.0% (AUC = 0.787) for lymph nodes. For glandular activity alone, scan accuracy was found to significantly improve with increasing Gleason score (P < 0.0001), and in a setting prior to treatment (P = 0.0005). No statistically significant differences were found between different scan groups with regards to seminal vesicle activity.

CONCLUSIONS

The results of this study provide substantiating evidence In-111 capromab pendetide can be used to accurately diagnose lymph node metastases from primary cancers of the prostate; however, they also suggest the test may have limited utility in diagnosing tumors within the prostate gland and seminal vesicles.

Influence of (11)C-choline PET/CT on the treatment planning for salvage radiation therapy in patients with biochemical recurrence of prostate cancer

BACKGROUND AND PURPOSE

The present study evaluates the incidence of (11)C-choline PET/CT positive findings in patients with recurrent prostate cancer referred for salvage radiotherapy (SRT) and the influence on the definition of the planning target volume (PTV).

MATERIAL AND METHODS

Thirty-seven patients treated with radical prostatectomy and referred to SRT to the prostatic fossa because of biochemical relapse, were analysed retrospectively. All patients underwent (11)C-choline PET/CT before radiotherapy. The influence of PET/CT on the extent of the PTV was analysed. The median total follow up after SRT was 51.2 months.

RESULTS

11/37 (30%) patients had a positive finding in the (11)C-choline PET/CT, 5 (13%) outside of the prostatic fossa (iliac lymph nodes), implicating an extension of the PTV. Patients with positive (11)C-choline PET/CT had a significant higher PSA value than patients with no pathologic uptake (p=0.03). Overall, at the end of follow up 56% of the patients had a PSA ≤ 0.2ng/ml and 44% had a biochemical relapse of prostate cancer.

CONCLUSIONS

(11)C-choline PET/CT detects abnormalities outside of the prostatic fossa in 13% of patients referred for SRT because of biochemical relapse after radical prostatectomy, affecting the extent of the PTV. Prospective studies need to be implemented to evaluate the benefit of SRT with a PTV based on (11)C-choline PET/CT.

Image-guided radiotherapy for prostate cancer: a prospective trial of concomitant boost using indium-111-capromab pendetide (ProstaScint) imaging

PURPOSE

To evaluate, in a prospective study, the use of (111)In-capromab pendetide (ProstaScint) scan to guide the delivery of a concomitant boost to intraprostatic region showing increased uptake while treating the entire gland with intensity-modulated radiotherapy for localized prostate cancer.

METHODS AND MATERIALS

From September 2002 to November 2005, 71 patients were enrolled. Planning pelvic CT and (111)In-capromab pendetide scan images were coregistered. The entire prostate gland received 75.6 Gy/42 fractions, whereas areas of increased uptake in (111)In-capromab pendetide scan received 82 Gy. For patients with T3/T4 disease, or Gleason score ≥8, or prostate-specific antigen level >20 ng/mL, 12 months of adjuvant androgen deprivation therapy was given. In January 2005 the protocol was modified to give 6 months of androgen deprivation therapy to patients with a prostate-specific antigen level of 10-20 ng/mL or Gleason 7 disease.

RESULTS

Thirty-one patients had low-risk, 30 had intermediate-risk, and 10 had high-risk disease. With a median follow-up of 66 months, the 5-year biochemical control rates were 94% for the entire cohort and 97%, 93%, and 90% for low-, intermediate-, and high-risk groups, respectively. Maximum acute and late urinary toxicities were Grade 2 for 38 patients (54%) and 28 patients (39%) and Grade 3 for 1 and 3 patients (4%), respectively. One patient had Grade 4 hematuria. Maximum acute and late gastrointestinal toxicities were Grade 2 for 32 patients (45%) and 15 patients (21%), respectively. Most of the side effects improved with longer follow-up.

CONCLUSION

Concomitant boost to areas showing increased uptake in (111)In-capromab pendetide scan to 82 Gy using intensity-modulated radiotherapy while the entire prostate received 75.6 Gy was feasible and tolerable, with 94% biochemical control rate at 5 years.

Imaging of prostate cancer with PET/CT and radioactively labeled choline derivates

PET- and PET/CT using [(11)C]- and [(18)F]-labeled choline derivates are increasingly being used for imaging of prostate cancer. The value of PET- and PET/CT with [(11)C]- and [(18)F]-labeled choline derivates in biochemical recurrence of prostate cancer has been examined in many studies and demonstrates an increasing importance. PET/CT, in comparison to PET, improves especially the lesion localization as well as characterization. Primary prostate cancer can be detected with moderate sensitivity using PET and PET/CT using [(11)C]- and [(18)F]-labeled choline derivates--the differentiation between benign prostatic hyperplasia, prostatitis, or high-grade intraepithelial neoplasia (HGPIN) is not always possible. At the present time, [(11)C]-choline PET/CT is not recommended in the primary setting but may be utilized in clinically suspected prostate cancer with repeatedly negative prostate biopsies, in preparation of a focused re-biopsy. Promising results have been obtained for the use of PET and PET/CT with [(11)C]- and [(18)F]-labeled choline derivates in patients with biochemical recurrence. The detection rate of choline PET and PET/CT for local, regional, and distant recurrence in patients with a biochemical recurrence shows a linear correlation with PSA value at the time of imaging and reaches about 75% in patients with PSA > 3 ng/ml. Even at PSA values below 1 ng/ml, the recurrence can be diagnosed with choline PET/CT in approximately one-third of the patients. PET and PET/CT with [(11)C]- and [(18)F]-choline derivates can be helpful in the clinical setting for choosing a therapeutic strategy in the sense of an individualized treatment: an early diagnosis of recurrence is crucial to the choice of optimal treatment. Especially important for the choice of treatment is the exact localization of the site of recurrence: local recurrence, recurrence as lymph node metastasis, or systemic recurrence, as it has direct influence on individual therapy. This article reviews the use of PET and PET/CT with [(11)C]- and [(18)F]-labeled choline derivates in prostate cancer imaging with special emphasis on patients with biochemical recurrence. We briefly provide an overview of PET tracers for prostate cancer imaging, the rationale of using choline derivatives for prostate cancer imaging and discuss the contribution of choline PET/CT in patients suffering from prostate cancer with an emphasis on recurrent disease. Furthermore, we provide an outlook on future prospects of choline PET/CT imaging for therapy guidance and monitoring in the framework of therapy individualization.

Salvage radiotherapy for patients with PSA relapse following radical prostatectomy: issues and challenges

A progressively rising level of serum prostate specific antigen (PSA) after radical prostatectomy (RP) invariably indicates the recurrence of prostate cancer. The optimal management of patients with post-RP PSA relapse has remained uncertain due to a wide variability in the natural course of post-RP PSA relapse and the inability to separate a recurrent disease confined to the prostate bed from that with occult distant metastasis. Management uncertainty is further compounded by the lack of phase III clinical studies demonstrating which therapeutic approach, if any, would prolong life with no significant morbidity. Radiotherapy has been the main therapeutic modality with a curative potential for patients with post-RP PSA relapse. This review article depicts issues and challenges in the management of patients with post-RP PSA relapse, presents the literature data for the efficacy of salvage radiotherapy, either alone or in combination of androgen ablation therapy, and discusses future directions that can optimize treatment strategies.

Modalities for imaging of prostate cancer

Prostate cancer is the second most common cause of cancer deaths among males in the United States. Prostate screening by digital rectal examination and prostate-specific antigen has shifted the diagnosis of prostate cancer to lower grade, organ confined disease, adding to overdetection and overtreatment of prostate cancer. The new challenge is in differentiating clinically relevant tumors from ones that may otherwise never have become evident if not for screening. The rapid evolution of imaging modalities and the synthesis of anatomic, functional, and molecular data allow for improved detection and characterization of prostate cancer. However, the appropriate use of imaging is difficult to define, as many controversial studies regarding each of the modalities and their utilities can be found in the literature. Clinical practice patterns have been slow to adopt many of these advances as a result. This review discusses the more established imaging techniques, including Ultrasonography, Magnetic Resonance Imaging, MR Spectroscopy, Computed Tomography, and Positron Emission Tomography. We also review several promising techniques on the horizon, including Dynamic Contrast-Enhanced MRI, Diffuse-Weighted Imaging, Superparamagnetic Nanoparticles, and Radionuclide Scintigraphy.

In vivo tumor grading of prostate cancer using quantitative 111In-capromab pendetide SPECT/CT

We have developed an in vivo method to quantify antibody uptake using (111)In-capromab pendetide SPECT combined with CT (SPECT/CT). Our goal was to evaluate this method for potential grading of prostate tumors.

METHODS

Our phantom experiments focused on the robustness of an advanced iterative reconstruction algorithm that involves corrections for photon attenuation, scatter, and geometric blurring caused by radionuclide collimators. The conversion factors between image values and tracer concentrations (in Bq/mL) were calculated from a uniform phantom filled with an aqueous solution of (111)InCl(3) using the same acquisition protocol and reconstruction parameters as for patient studies. In addition, the spatial resolution of the reconstructed images was measured from a point source phantom. The measured spatial resolution was modeled into a point-spread function, and the point-spread function was implemented in a deconvolution-based partial-volume-error correction algorithm. The recovery capability to correctly estimate true tracer concentrations was tested using prostatelike and bladderlike lesion phantoms fitted in the modified National Electrical Manufacturers Association/International Electrotechnical Commission body phantom. Patients with biopsy-proven prostate cancer (n = 10) who underwent prostatectomy were prospectively enrolled in the preoperative SPECT/CT studies at the San Francisco Veterans Affairs Medical Center. The CT portion of SPECT/CT was used to generate CT-based attenuation maps and as an anatomic localization tool for clinical interpretation. Pathologic Gleason grades were compared with in vivo antibody uptake value (AUV) normalized by injected dose, effective half-life, and injection-scan time difference. AUVs were calculated in each lobe of the prostate gland with cylindric volumes of interest having dimensions of 1.5 cm in both diameter and height.

RESULTS

Reconstructed SPECT images further corrected by the deconvolution-based partial-volume-error correction could recover tracer concentrations up to 90% of true values in measurements of phantom volumes as small as 7.77 mL. From patient studies, there was a statistically significant correlation (rho = 0.71, P = 0.033) between higher AUVs (from either left or right lobe) and higher components of pathologic Gleason scores.

CONCLUSION

Our results strongly indicate potential for noninvasive prostate tumor grading using quantitative (111)In-capromab pendetide SPECT/CT.

[Which imaging methods should be used prior to salvage radiotherapy after prostatectomy for prostate cancer?]

Prostatectomy is one of the most widely used methods for treatment of adenocarcinoma of the prostate. According to anatomopathological criteria, between 10 and 40% of patients will display biochemical relapse in the absence of adjuvant radiotherapy. Anatomopathological and biochemical criteria are powerful tools for selecting patients for salvage radiotherapy. The aim of this article is to review literature on the latest progress in radiological and nuclear medicine techniques and their performance levels, in order to determine local, regional and metastatic relapses associated with the techniques and specify the radiotherapy target volume. Magnetic resonance imaging (MRI) displays the best sensitivity and specificity for examination of the prostate bed and enables simultaneous assessment of the pelvic region - thus diminishing the utility of computed tomography. The performance levels of MRI will probably continue to improve, with the use of dynamic MRI and MR spectroscopy. Despite the development of new markers like (11)C and (18)F choline and acetate, the sensitivity of positron emission tomography is still low. Prospective studies with an appropriate methodology are necessary for specifying the technique's value in this context.

Infectious complications associated with monoclonal antibodies and related small molecules

Biologics are increasingly becoming part of routine disease management. As more agents are developed, the challenge of keeping track of indications and side effects is growing. While biologics represent a milestone in targeted and specific therapy, they are not without drawbacks, and the judicious use of these "magic bullets" is essential if their full potential is to be realized. Infectious complications in particular are not an uncommon side effect of therapy, whether as a direct consequence of the agent or because of the underlying disease process. With this in mind, we have reviewed and summarized the risks of infection and the infectious disease-related complications for all FDA-approved monoclonal antibodies and some related small molecules, and we discuss the probable mechanisms involved in immunosuppression as well as recommendations for prophylaxis and treatment of specific disease entities.

Bone imaging in prostate cancer

Bone metastases of solid tumors are common, and about 80% of them occur in patients with breast, lung or prostate cancer. Bone metastases can be suspected clinically and by laboratory tests; however, a final diagnosis relies on radiographic evidence. Bone metastases of prostate cancer usually have osteoblastic characteristics, manifested by pathological bone resorption and formation. Conventional bone scans (e.g. with (99m)Tc-labeled methylene diphosphonate) are preferred to plain-film radiography for surveillance of the entire skeleton. Radiologic diagnosis of bone metastases, particularly in patients with low burden of disease, is difficult because noncancerous bone lesions that mimic cancer are common. Conventional bone scans are limited by their low sensitivity and high false-negative rate (up to 40%) compared with advanced bone-imaging modalities such as PET, PET-CT and MRI, which might assist or replace conventional scanning methods. The correct diagnosis of bone involvement in prostate cancer is crucial to assess the effects of therapy on the primary tumor, the patient's prognosis, and the efficacy of bone-specific treatments that can reduce future bone-associated morbidity. In addition, predictive tools such as nomograms enable the identification of patients at risk of bone involvement during the course of their disease. Such tools may limit treatment costs by avoidance of unnecessary tests and might reduce both short-term and long-term complication rates.

Adjuvant and salvage radiotherapy after prostatectomy for prostate cancer: a literature review

PURPOSE

Given that postprostatectomy recurrence of prostate cancer occurs in 10-40% of patients, the best use of immediate postoperative radiotherapy (RT) in high-risk patients and salvage RT for biochemical recurrence remains a topic of debate. We assessed the levels of evidence (in terms of efficacy, prognostic factors, and toxicity) for the following treatment strategies: immediate postoperative RT alone, salvage RT alone, and the addition of androgen deprivation therapy to the two RT strategies.

METHODS AND MATERIALS

A systematic literature search for controlled randomized trials, noncontrolled trials, and retrospective studies between 1990 and 2008 was performed on PubMed, CancerLit, and MEDLINE. Only relevant articles that had appeared in peer-reviewed journals were selected. We report on the levels of evidence (according to the National Cancer Institute guidelines) supporting the various treatment strategies.

RESULTS

Immediate postoperative RT improves biochemical and clinical progression-free survival (Level of evidence, 1.ii) but has no significant effect on metastasis-free survival or overall survival. A pathologic review is of particular importance for correctly analyzing the treatment strategies. Low-grade morbidity has been significantly greater in the postoperative groups, but no severe toxicity has been observed. The influence of immediate postoperative RT on postprostatectomy continence appears to be slight; therefore, immediate postoperative RT should be considered in patients with major risk factors for local relapse (Level of evidence, 1.ii). On the basis of extensive retrospective data, salvage RT is effective in biochemical relapse after prostatectomy; some patients with few adverse prognostic factors might also benefit from salvage RT (Level of evidence, 3.ii). The addition of androgen deprivation therapy to immediate postoperative or salvage RT has only been supported by weak, retrospective data (Level of evidence, 3.ii).

CONCLUSION

Prospective randomized trials are needed to compare immediate postoperative RT with salvage RT and to assess the value of androgen deprivation therapy in this setting.

N-[N-[(S)-1,3-Dicarboxypropyl]carbamoyl]-4-[18F]fluorobenzyl-L-cysteine, [18F]DCFBC: a new imaging probe for prostate cancer

PURPOSE

Previously, we showed successful imaging of xenografts that express the prostate-specific membrane antigen (PSMA) using small-animal positron emission tomography (PET) and the radiolabeled PSMA inhibitor N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-[11C]methyl-l-cysteine. Herein, we extend that work by preparing and testing a PSMA inhibitor of the same class labeled with fluorine-18.

EXPERIMENTAL DESIGN

N-[N-[(S)-1,3-Dicarboxypropyl]carbamoyl]-4-[18F]fluorobenzyl-l-cysteine ([18F]DCFBC) was prepared by reacting 4-[18F]fluorobenzyl bromide with the precursor (S)-2-[3-[(R)-1-carboxy-2-mercaptoethyl]ureido]-pentanedioic acid in ammonia-saturated methanol at 60 degrees C for 10 min followed by purification using C-18 reverse-phase semipreparative high-performance liquid chromatography. Severe combined immunodeficient mice bearing a s.c. PSMA+ PC-3 PIP tumor behind one shoulder and a PSMA(-) PC-3 FLU tumor behind the other shoulder were injected via the tail vein with either 1.85 MBq (50 microCi) of [18F]DCFBC for ex vivo biodistribution or 7.4 MBq (200 microCi) for imaging. For biodistribution, mice were sacrificed at 5, 15, 30, 60, and 120 min. Tumor, blood, and major organs were harvested and weighed, and radioactivity was counted. Imaging was done on the GE eXplore Vista small-animal PET scanner by collecting 12 consecutive 10-min frames.

RESULTS

Radiochemical yield for [18F]DCFBC averaged 16 +/- 6% (n = 8) from 4-[18F]fluorobenzyl bromide. Specific radioactivities ranged from 13 to 133 GBq/micromol (350-3,600 Ci/mmol) with an average of 52 GBq/micromol (1,392 Ci/mmol; n = 6). Biodistribution and imaging studies showed high uptake of [18F]DCFBC in the PIP tumors with little to no uptake in FLU tumors. High radiopharmaceutical uptake was also seen in kidneys and bladder; however, washout of radioactivity from these organs was faster than from the PIP tumors. The maximum PIP tumor uptake was 8.16 +/- 2.55% injected dose per gram, achieved at 60 min after injection, which decreased to 4.69 +/- 0.89 at 120 min. The PIP tumor to muscle ratio was 20 at 120 min after injection. Based on the mouse biodistribution, the dose-limiting organ is the kidneys (human estimated absorbed dose: 0.05 mGy/MBq; 0.2 rad/mCi).

CONCLUSION

[18F]DCFBC localizes to PSMA+-expressing tumors in mice, permitting imaging by small-animal PET. This new radiopharmaceutical is an attractive candidate for further studies of PET imaging of prostate cancer.

The role of imaging in the detection of prostate cancer local recurrence after radiation therapy and surgery

PURPOSE OF REVIEW

The aim of this article is to review novel MRI and nuclear medicine methods for detecting and planning salvage treatment for prostate cancer local recurrence after radical prostatectomy or radiation therapy.

RECENT FINDINGS

Traditional methods for detecting local recurrence (i.e., digital rectal exam or transrectal ultrasound and digital rectal exam or transrectal ultrasound-guided biopsy) have limited accuracy in determining the presence and extent of local recurrence and therefore have limited ability to guide salvage therapy. Recent studies indicate that conventional T1 and T2-weighted prostate MRI could improve the detection of recurrent prostate cancer after radical prostatectomy or radiation therapy and salvage treatment planning. Promising new sequences could further increase the accuracy of MRI. In addition, the use of technically improved PET/computed tomography scanners with new tracers like (11)C and (18)F choline and acetate might offer better assessment of recurrent prostate cancer than (18)F-2-fluoro-D-deoxyglucose-PET and monoclonal antibody imaging with the prostate specific membrane antigen antibody (111)In-capromab pendetide (ProstaScint).

SUMMARY

With systemic therapies for recurrent prostate cancer after radical prostatectomy or radiation therapy being noncurative, the application of MRI and nuclear medicine modalities can help to identify patients who have isolated local recurrence amenable to salvage treatment.

Indium-111 capromab pendetide in the management of recurrent prostate cancer

The provision of accurate prognostic information is a long-standing goal for effective management of prostate adenocarcinoma. Nontargeted imaging modalities are less efficient at detecting slow-growing prostate cancers. Prostate-specific membrane antigen has emerged as a superior biomarker, especially for the evaluation of metastatic spread. Advances in imaging technology have focused clinical interest on indium-111 capromab ((111)In capromab) pendetide, a radioimmunoconjugate that detects prostate-specific membrane antigen expression in vivo. Single-photon emission computed tomography capromab pendetide images, fused with those generated by computed tomography or magnetic resonance, have engendered improvements in localization accuracy by correlating high signal intensity with anatomic structures. In long-term outcomes studies, fused (111)In capromab pendetide scans have delivered significant benefits for patient selection and improved treatment of prostate cancer.

Single photon emission computerized tomography with capromab pendetide plus computerized tomography image set co-registration independently predicts biochemical failure

PURPOSE

We evaluate the usefulness of pretreatment (111)Indium capromab pendetide (ProstaScint) planar imaging (immunoscintigraphy) plus single photon emission tomography co-registration with computerized tomography scans to detect occult metastatic disease and predict for biochemical failure, in a cohort of patients with a clinical diagnosis of localized adenocarcinoma of the prostate referred for primary radiotherapy.

MATERIALS AND METHODS

Patients were followed after radiotherapy for evidence of biochemical failure using 2 criteria of prostate specific antigen clinical nadir +2 ng/ml and American Society for Therapeutic Radiology and Oncology Consensus definitions. Median followup was 58.8 months (mean 64.8). Clinical risk factors defined 3 risk groups of high (51), intermediate (72) and low (116).

RESULTS

Overall biochemical failure was 18.3% vs 11.8% by the 2-BFC at 8-year actuarial analysis with 58.8 months median followup. By the CN +2 definition the control date for the cohort is 34.8 months. Pretreatment SPECT/CT suggested prostate cancer metastasis (22), seminal vesicle extension (20) and organ confined disease (197). Biochemical failure in patients having extra-periprostatic metastatic prostate cancer, seminal vesicle extension and organ confined disease uptake on SPECT/CT was 43.2%, 16.0% vs 14.7% (p = 0.0006); and 33.3%, 15.0% vs 8.7% (p = 0.0017) by the 2-BFC, respectively. Cox multiple regression analysis demonstrated that a finding of extra-periprostatic metastatic prostate on SPECT/CT significantly predicted a 4.2-fold greater risk (p = 0.0012) and a 4.5-fold greater risk (p = 0.0011) of failure by the 2-BFC than organ confined disease adjusting for treatment and risk group.

CONCLUSIONS

Unconfirmed findings of extra-periprostatic metastatic prostate cancer on SPECT/CT immunoscintigraphy independently and significantly predicted an increased risk of biochemical failure in patients presenting for radiotherapy with a clinical diagnosis of localized prostate cancer.

ProstaScint and its role in the diagnosis of prostate cancer

Cancer of the prostate is the most common cancer in males accounting for 33% of newly diagnosed cases. It is the second leading cause of cancer death in American males. The prevalence of prostate cancer increases most rapidly with age and the incidence (unlike other cancers) continues to rise with advancing age. Death due to this cancer is almost invariably the result of failure to control metastatic disease. In addition, several studies have demonstrated that over 30% of patients will experience biochemical recurrence after surgery with long-term (more than 10 years) follow-up. Information regarding the location of the cancer is critical to the success of initial therapy when deciding between local versus systemic treatment options in the newly diagnosed patient. For patients who have already undergone definitive treatment, the localization of recurrent tumor, evidenced by an elevation of prostate-specific antigen, is difficult unless the tumor burden is large enough to be detected on conventional radiographic studies or digital rectal examination and prostatic fossa biopsy. ProstaScint is a diagnostic tool used to detect metastatic prostate cancer in lymph nodes or other sites. This article provides an overview on the uses of ProstaScint in the assessment of patients with recurrent or metastatic prostate cancer.

Indications et résultats de la radiothérapie de rattrapage dans les cancers de la prostate

Salvage radiotherapy after radical prostatectomy can be delivered either in case of biochemical recurrence or in situation of clinical relapse. In this last case, results are poor regarding disease-free survival but quite interesting regarding the local control rate. The best situation for salvage radiotherapy is still the rising PSA case: half of the patients can be in complete remission at 5 years after 65 Gy radiotherapy. The role of hormone therapy combined with salvage radiotherapy is still under investigation.

The role of indium-111 radioimmunoscintigraphy in post-radical retropubic prostatectomy management of prostate cancer patients

Indium-111 radioimmunoscintigraphy (RIS) has an increasing role in the treatment of prostate cancer and is most commonly performed at this disease site using labeled monoclonal antibody against prostate-specific membrane antigen. There are many limitations of RIS, including low spatial resolution, low diagnostic yield and limited availability. Despite these limitations, the efficacy of RIS has been demonstrated in many clinical studies, including multi-institutional investigations. The highest sensitivity and specificity of RIS appears to be in the post-radical retropubic prostatectomy (post-RRP) setting. RIS has recently been explored for its role in clinical radiotherapy decision-making, and was found to have a significant impact in selecting patients for radiotherapy and for the general radiotherapy treatment volume definition. RIS has also recently been explored for its role in radiotherapy planning and was found to impact clinical target volume design. However, manual editing of the RIS volume is still necessary when projected into the radiotherapy-planning scan, as there is often overlap in the RIS-defined uptake regions with normal structures (rectum, bladder and symphysis bone marrow). The impact of RIS on biochemical control has been explored, with studies in this area yielding conflicting results. It appears that the maximum impact of RIS is possible when areas of labeled antibody uptake regions are co-registered with the radiotherapy-planning computed tomography scan. The larger RIS-guided target volumes do not appear to be prohibitive in increasing radiotherapy-related toxicity. Future directions of the use of RIS for post-RRP prostate cancer are discussed.