Positive [11C]choline and negative [18F]FDG with positron emission tomography in recurrence of prostate cancer

Non-FDG PET/CT

The major applications for molecular imaging with PET in clinical practice concern cancer imaging. Undoubtedly, 18F-FDG represents the backbone of nuclear oncology as it remains so far the most widely employed positron emitter compound. The acquired knowledge on cancer features, however, allowed the recognition in the last decades of multiple metabolic or pathogenic pathways within the cancer cells, which stimulated the development of novel radiopharmaceuticals. An endless list of PET tracers, substantially covering all hallmarks of cancer, has entered clinical routine or is being investigated in diagnostic trials. Some of them guard significant clinical applications, whereas others mostly bear a huge potential. This chapter summarizes a selected list of non-FDG PET tracers, described based on their introduction into and impact on clinical practice.

Molecular imaging in oncology

The major application for PET imaging in clinical practice is represented by cancer imaging and (18)F-FDG is the most widely employed positron emitter compound. However, some diseases cannot be properly evaluated with this tracer and thus there is the necessity to develop more specific compounds. The last decades were a continuous factory for new radiopharmaceuticals leading to an endless list of PET tracers; however, just some of them guard diagnostic relevance in routine medical practice. This chapter describes a selected list of non-FDG PET tracers, basing on their introduction into and impact on clinical practice.

Functional imaging for prostate cancer: therapeutic implications

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

[11C]Choline PET/CT detection of bone metastases in patients with PSA progression after primary treatment for prostate cancer: comparison with bone scintigraphy

PURPOSE

The aim of this study was to evaluate the clinical usefulness of [(11)C]choline positron emission tomography (PET)/CT in comparison with bone scintigraphy (BS) in detecting bone metastases (BM) of patients with biochemical progression after radical treatment for prostate cancer (PCa).

METHODS

Seventy-eight consecutive patients with biochemical progression of PCa (mean prostate-specific antigen 21.1 ng/ml, range 0.2-500.0 ng/ml) referred for both [(11)C]choline PET/CT and BS for restaging purposes were retrospectively analysed. The diagnostic accuracy of [(11)C]choline PET/CT and BS was assessed by using morphological imaging and/or follow-up as standards of reference. As equivocal findings were found, the accuracy analysis was performed twice, once including them as positive and once as negative. A separate analysis was also performed in hormone-resistant patients and data compared with those of patients who did not receive anti-androgenic treatment.

RESULTS

Equivocal findings occurred in 1 of 78 (1%) cases in [(11)C]choline PET/CT and in 21 of 78 (27%) cases in BS. Depending on their attribution as either positive or negative, the ranges of sensitivity, specificity, positive predictive value, negative predictive value and accuracy for [(11)C]choline PET/CT were 89-89%, 98-100%, 96-100%, 94-96% and 95-96%, respectively. For BS they were 100-70%, 75-100%, 68--100%, 100-86% and 83-90%, respectively. Concordant findings between [(11)C]choline PET/CT and BS occurred in 55 of 78 (71%) cases. The accuracy of [(11)C]choline PET/CT did not significantly (p = 0.30) differ between hormone-resistant patients (97%) and those who did not receive anti-androgenic treatment (95%).

CONCLUSION

In clinical practice, [(11)C]choline PET/CT may not replace BS because of its lower sensitivity. However, for its high specificity, [(11)C]choline PET/CT positive findings may accurately predict the presence of BM. Equivocal findings are more frequent in BS than [(11)C]choline PET/CT.

Prostate cancer

Prostate cancer is biologically and clinically a heterogeneous disease and its imaging evaluation will need to be tailored to the specific phases of the disease in a patient-specific, risk-adapted manner. We first present a brief overview of the natural history of prostate cancer before discussing the role of various imaging tools, including opportunities and challenges, for different clinical phases of this common disease in men. We then review the preclinical and clinical evidence on the potential and emerging role of positron emission tomography with various radiotracers in the imaging evaluation of men with prostate cancer.

Non FDG PET

2- [(18)F]-fluoro-2-deoxy-D-glucose (FDG) is the radiopharmaceutical most frequently used for clinical positron emission tomography (PET). However, FDG cannot be used for many oncological, cardiological, or neurological conditions, either because the abnormal tissue does not concentrate it, or because the tissues under investigation demonstrate high physiological glucose uptake. Consequently, alternative PET tracers have been produced and introduced into clinical practice. The most important compounds in routine practice are (11)C-choline and (18)F-choline, mainly for the evaluation of prostate cancer; (1)C-methionine for brain tumours; (118)F-DOPA ((18)F-deoxiphenilalanine) for neuroendocrine tumours and movement disorders; (68)Ga-DOTANOC (tetraazacyclododecanetetraacetic acid-[1-Nal3]-octreotide) and other somatostatin analogues for neuroendocrine tumours; 11C-acetate for prostate cancer and hepatic masses and 18F-FLT (3-deoxy-3-fluorothymidine) for a number of malignant tumours. Another impetus for the development of new tracers is to enable the investigation of biological processes in tumours other than glucose metabolism. This is especially important in the field of response assessment, where there are new agents that are targeted more specifically at angiogenesis, hypoxia, apoptosis and other processes.

[(11)C]Choline positron emission tomography/computed tomography for staging and restaging of patients with advanced prostate cancer

INTRODUCTION

To evaluate [(11)C]Choline positron emission tomography (PET)/computed tomography (CT) for staging and restaging of patients with advanced prostate cancer and to compare the diagnostic performance of PET, CT and PET/CT.

METHODS

Forty-five consecutive patients with advanced prostate cancer underwent [(11)C]Choline-PET/CT between 5/2004 and 2/2006.

RESULTS

Overall, 295 lesions were detected: PET alone, 178 lesions; diagnostic CT, 221 lesions; PET/CT (low-dose CT), 272 lesions; PET/CT (diagnostic CT), 295 lesions. Two thirds of the lesions were located in the bone; one third in the prostate, lymph nodes, periprostatic tissue and soft tissue (lung, liver). The use of diagnostic CT did not result in a statistically significant difference with respect to lesion localization certainty and lesion characterization (P=.063, P=.063). PET-negative but PET/CT-positive lesions were mostly localized in the bone (78%, 91/117) as were PET-positive and CT-negative lesions (72%, 53/74). Of the latter, 91% (48/53) represented bone marrow and 9% (5/53) cortical involvement.

CONCLUSIONS

Staging and restaging with [(11)C]Choline PET/CT in patients with advanced prostate cancer improve the assessment of local and regional recurrent as well as metastatic disease including skeletal manifestations. [(11)C]Choline PET/CT (with a low-dose CT) results in improved localization and lesion characterization. [(11)C]Choline PET/CT provides an added value for skeletal manifestations. [(11)C]Choline PET/CT changed disease management in 11 (24%) of 45 patients with advanced prostate cancer.

Positron Emission Tomography (PET) radiotracers in oncology--utility of 18F-Fluoro-deoxy-glucose (FDG)-PET in the management of patients with non-small-cell lung cancer (NSCLC)

PET (Positron Emission Tomography) is a nuclear medicine imaging method, frequently used in oncology during the last years. It is a non-invasive technique that provides quantitative in vivo assessment of physiological and biological phenomena. PET has found its application in common practice for the management of various cancers.Lung cancer is the most common cause of death for cancer in western countries.This review focuses on radiotracers used for PET scan with particular attention to Non Small Cell Lung Cancer diagnosis, staging, response to treatment and follow-up.

Conventional and novel PET tracers for imaging in oncology in the era of molecular therapy

In the last ten years, the development of several novel targeted drugs and the refinement of state of the art technologies such as the genomics and proteomics and their introduction to clinical practice have revolutionized the management of patients affected by cancer. However, everyday practice points out several clinical questions: the difficulty of response assessment to new drugs especially using standard RECIST criteria that do not provide information on biological, vascular or metabolic variations; the inadequate selection of patients who are likely to benefit from a targeted therapy excluding those with breast cancer and gastrointestinal stromal tumours; the need to know the global biological background of diseases especially in metastatic setting using repeatable non-invasive procedures. Molecular imaging could provide information on in vivo distribution of biological markers in response to targeted therapy and could improve the selection of patients before therapies. The aim of this review is to analyze the current role of conventional and innovative positron emission tomography (PET) radiotracers in clinical practice and to explore the promising perspectives of molecular imaging in cancer research.

Chiral dimethylamine flutamide derivatives—modeling, synthesis, androgen receptor affinities and carbon-11 labeling

Most prostate cancers are androgen dependent upon initial diagnosis. On the other hand, some very aggressive forms of prostate cancer were shown to have lost the expression of the androgen receptor (AR). Although the AR is routinely targeted in endocrine treatment, the clinical outcome remains suboptimal. Therefore, it is crucial to demonstrate the presence and activity of the AR in each case of prostate cancer, before and after treatment. While noninvasive positron emission tomography (PET) has the potential to determine AR expression of tumor cells in vivo, fully optimized PET imaging agents are not yet available. Based on molecular modeling, three novel derivatives of hydroxyflutamide (Compounds 1-3) were designed and synthesized. They contain an electron-rich group (dimethylamine) located on the methyl moiety, which may confer a better stability to the molecule in vivo. Compounds 1-3 have AR binding that is similar or higher than that of the currently used commercial drugs. An automated carbon-11 radiolabeling route was developed, and the compounds were successfully labeled with a 10-15% decay-corrected radiochemical yield, 99% radiochemical purity and a specific activity of 4Ci/mumol end of bombardment (n=15). These labeled biomarkers may facilitate the future quantitative molecular imaging of AR-positive prostate cancer using PET and may also allow for image-guided treatment of prostate cancer.

Parameters for Treatment Decisions for Salvage Radiation Therapy

Radical prostatectomy (RP) is the most common primary treatment for prostate cancer. About 40% of those with high-risk pathologic features, such as a positive margin or seminal vesicle involvement, will develop biochemical failure at some point in the future. Radiotherapy (RT), with or without concurrent androgen deprivation, has been used liberally in the management of men with a rising prostate-specific antigen (PSA) after RP, based mostly on relatively small retrospective series. Factors such as the prostatectomy Gleason score, seminal vesicle invasion, absolute pre-RT PSA level, and pre-RT PSA doubling time are emerging as important determinants of outcome after RT. These factors should be used as a guide to the options of local therapy alone (RT), local therapy plus systemic therapy (typically androgen deprivation therapy), and systemic therapy alone.

Prostate cancer PET bioprobes: Synthesis of [18F]-radiolabeled hydroxyflutamide derivatives

Approximately 80-90% of prostate cancers are androgen dependent at initial diagnosis. The androgen receptor (AR) is present in most advanced prostate cancer specimens and is believed to have a critical role in its development. Today, treatment of prostate cancer is done by inhibition of AR using antiandrogens such as flutamide (pro-drug of hydroxyflutamide), nilutamide, and bicalutamide. However, there is currently no noninvasive imaging modalities to detect, guide, and monitor specific treatment of AR-positive prostate cancer. (R)-3-Bromo-N-(4-fluoro-3-(trifluoromethyl)phenyl)-2-hydroxy-2-methyl-propanamide [18F]-1 and N-(4-fluoro-3-(trifluoromethyl)phenyl)-2-hydroxy-2-methylpropanamide [18F]-2, derivatives of hydroxyflutamide, were synthesized as a fluorine-containing imaging agent candidates. A three-step fluorine-18 radiosynthesis route was developed, and the compounds were successfully labeled with a 10+/-3% decay corrected radiochemical yield, 95% radiochemical purity, and a specific activity of 1500+/-200 Ci/mmol end of bombardment (n = 10). These labeled biprobes not only may enable for the future quantitative molecular imaging of AR-positive prostate cancer using positron emission tomography but may also allow for image-guided treatment of prostate cancer.

Wertigkeit der Bildgebung für die Lymphknotenmetastasierung beim Nierenzell-, Blasen-, Prostata- und Peniskarzinom sowie dem Hodentumor

Computed tomography (CT) imaging is the standard method for the assessment of lymph node metastases in renal cell and testicular cancer. In bladder cancer and prostate cancer the results of CT are not convincing due to a large number of false-negative findings and the prognostic relevance of undetected metastases. For both entities recent studies revealed that MR lymphography using iron oxide particles allows the detection of small metastatic lymph nodes. For penile cancer reliable results for imaging of lymph node metastases do not exist. PET imaging using [(18)F]-fluorodeoxyglucose (FDG) is the modality of choice in therapy control of seminomas but has no defined value in other urological malignancies. PET with [(11)C] choline and [(11)C] acetate offers great potential in staging and restaging of prostate cancer. Further investigations are necessary to determine the role of these new methods.

Backbone metal cyclization: Novel 99mTc labeled GnRH analog as potential SPECT molecular imaging agent in cancer

Gonadotropin-releasing hormone (GnRH) is a decapeptide secreted to the pituitary where it binds to specific receptors on the gonadotropes to regulate gonadotropic hormones (luteinizing hormone (LH) and follicle-stimulating hormone (FSH)) synthesis and secretion. Specific GnRH receptors are overexpressed in breast, prostatic, ovarian, and other tumors. The aim of this study was to synthesize a cyclic GnRH analog with high affinity to GnRH receptors that can be radiolabeled with 99mTc. A precyclic GnRH analog, [Cys-Gly]1[D-Ala]6[N(alpha)(eta-Cys-amino hexyl)]10GnRH (Gn-2), containing two hemi-chelator groups was synthesized. It was cyclized applying the recently reported backbone metal cyclization (BMC) approach, to obtain cyclo(Re(O)1-10)[Cys-Gly]1[D-Ala]6[N(alpha)(eta-Cys-amino hexyl)]10GnRH (cyclo[Re(O)-Gn-2]). For comparative evaluations, Gn-2 was oxidized on-resin to yield cyclo(S-S,1-10)[Cys-Gly]1[D-Ala]6[N(alpha)(eta-Cys-amino hexyl)]10GnRH, (cyclo[S-S-Gn-2]). The binding affinity of cyclo[Re(O)-Gn-2] to rat pituitary membranes showed IC50 of 50 nM, compared to IC50 = 10 nM in the native GnRH. Cyclo(99mTc(O)1-10)[Cys-Gly]1[D-Ala]6[N(alpha)(eta-Cys-amino hexyl)]10GnRH (cyclo[99mTc(O)-Gn-2]) was synthesized from Gn-2 and showed similar chromatographic behavior to its rhenium surrogate.

Uptake rates of 18F-fluorodeoxyglucose and 11C-choline in lung cancer and pulmonary tuberculosis: a positron emission tomography study

STUDY OBJECTIVE

The purpose of this study was to examine the uptake rates of (18)F-fluorodeoxyglucose (FDG) and (11)C-choline in patients with lung cancer, pulmonary tuberculosis, and atypical mycobacterial infection of the lung by positron emission tomography (PET) scanning with relation to their tumor size.

DESIGN

Ninety-seven patients with untreated lung cancer, 14 patients with untreated pulmonary tuberculosis, and 5 patients with untreated atypical mycobacterial infection were examined. The diagnosis of lung cancer was confirmed pathologically after biopsy and surgery. The diagnosis of tuberculosis and atypical mycobacterial infection was confirmed by bacterial culture. The uptake rates of FDG and (11)C-choline were presented quantitatively as the standardized uptake value (SUV).

SETTING

International Medical Center of Japan.

RESULTS

In lung cancer patients, the SUV of FDG increased with increasing tumor size, whereas the SUV of (11)C-choline was almost constant at around 3.5 for every tumor size. In tuberculosis patients, the SUV of FDG increased with increasing tumor size, whereas the SUV of (11)C-choline was almost constant at around 2 for every tumor size. In atypical mycobacterial infection patients, the SUV of FDG and the SUV of (11)C-choline were equally low at around < or = 2.

CONCLUSION

The differences in the SUVs of FDG and (11)C-choline in patients with lung cancer, tuberculosis, and atypical mycobacterial infection for the same tumor size (tumor size, > 1.5 cm) were distinct. In lung cancer patients, the SUVs of both FDG and (11)C-choline were high. In tuberculosis patients, the SUV of FDG was high, but the SUV of (11)C-choline was low. In atypical mycobacterial infection patients, the SUVs of both FDG and (11)C-choline were low. It may be possible to apply this principle to make a presumptive diagnosis of a solitary pulmonary nodule if it is too small to make a definitive diagnosis pathologically and bacteriologically.