The dual-isotope ProstaScint imaging procedure: clinical experience and staging results in 145 patients

Current and potential roles of immuno-PET/-SPECT in CAR T-cell therapy

Chimeric antigen receptor (CAR) T-cell therapies have evolved as breakthrough treatment options for the management of hematological malignancies and are also being developed as therapeutics for solid tumors. However, despite the impressive patient responses from CD19-directed CAR T-cell therapies, ~ 40%-60% of these patients' cancers eventually relapse, with variable prognosis. Such relapses may occur due to a combination of molecular resistance mechanisms, including antigen loss or mutations, T-cell exhaustion, and progression of the immunosuppressive tumor microenvironment. This class of therapeutics is also associated with certain unique toxicities, such as cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and other "on-target, off-tumor" toxicities, as well as anaphylactic effects. Furthermore, manufacturing limitations and challenges associated with solid tumor infiltration have delayed extensive applications. The molecular imaging modalities of immunological positron emission tomography and single-photon emission computed tomography (immuno-PET/-SPECT) offer a target-specific and highly sensitive, quantitative, non-invasive platform for longitudinal detection of dynamic variations in target antigen expression in the body. Leveraging these imaging strategies as guidance tools for use with CAR T-cell therapies may enable the timely identification of resistance mechanisms and/or toxic events when they occur, permitting effective therapeutic interventions. In addition, the utilization of these approaches in tracking the CAR T-cell pharmacokinetics during product development and optimization may help to assess their efficacy and accordingly to predict treatment outcomes. In this review, we focus on current challenges and potential opportunities in the application of immuno-PET/-SPECT imaging strategies to address the challenges encountered with CAR T-cell therapies.

Multi-molecule imaging and inter-molecular imaging in nuclear medicine

Multi-molecule imaging and inter-molecular imaging are not fully implemented yet, however, can become an alternative in nuclear medicine. In this review article, we present arguments demonstrating that the advent of the Compton positron emission tomography (Compton-PET) system and the invention of the quantum chemical sensing method with double photon emission imaging (DPEI) provide realistic perspectives for visualizing inter-molecular and multi-molecule in nuclear medicine with MeV photon. In particular, the pH change of InCl3 solutions can be detected and visualized in a three-dimensional image by combining the hyperfine electric quadrupole interaction sensing and DPEI. Moreover, chemical states, such as chelating, can be detected through angular correlation sensing. We argue that multi-molecule and chemical sensing could be a realistic stream of research in future nuclear medicine.

Simultaneous multi-nuclide imaging via double-photon coincidence method with parallel hole collimators

Multi-tracer imaging can provide useful information in the definitive diagnosis and research of medical, biological, and pharmaceutical sciences. Single-photon emission computed tomography (SPECT) is one of the nuclear medicine imaging modalities widely used for diagnosis or medical research and has a multi-tracer imaging capability. One of the drawbacks of multi-tracer imaging is crosstalk from other gamma rays, which affects the reconstructed image. Scattering correction methods, such as the dual- and triple-energy window methods, are used for conventional SPECT imaging to reduce the background caused by the crosstalk. This study proposes another crosstalk reduction method. Some nuclides emit two or more gamma rays through intermediate levels. Thus, detecting these gamma rays with the coincidence method allows us to distinguish a true gamma ray signal and a background signal. The nuclide position can be estimated at the intersection of two gamma rays using collimators. We demonstrate herein simultaneous ¹¹¹In and ¹⁷⁷Lu imaging via the double-photon coincidence method using GAGG detectors and parallel hole collimators. The double-photon coincidence method greatly reduces the background caused by other gamma rays and offers higher-quality images than does conventional imaging.

SPECT/CT and tumour imaging

Scintigraphic techniques are sensitive imaging modalities in the diagnosis and follow-up of cancer patients providing the functional and metabolic activity characteristics of the tumour. Hybrid SPECT/CT improves the diagnostic accuracy of these well-established imaging techniques by precise anatomical localization and characterization of morphological findings, differentiation between foci of physiological and pathological tracer uptake, resulting in a significant impact on patient management and more definitive interpretations. The use of SPECT/CT has been studied in a variety of applications in tumour imaging which are reviewed in this article. By combining functional and anatomical information in a single imaging session, SPECT/CT has become a one-stop cancer imaging modality.

A limiting factor for the progress of radionuclide-based cancer diagnostics and therapy--availability of suitable radionuclides

Advances in diagnostics and targeted radionuclide therapy of haematological and neuroendocrine tumours have raised hope for improved radionuclide therapy of other forms of disseminated tumours. New molecular target structures are characterized and this stimulates the efforts to develop new radiolabelled targeting agents. There is also improved understanding of factors of importance for choice of appropriate radionuclides. The choice is determined by physical, chemical, biological, and economic factors, such as a character of emitted radiation, physical half-life, labelling chemistry, chemical stability of the label, intracellular retention time, and fate of radiocatabolites and availability of the radionuclide. There is actually limited availability of suitable radionuclides and this is a limiting factor for further progress in the field and this is the focus in this article. The probably most promising therapeutic radionuclide, 211At, requires regional production and distribution centres with dedicated cyclotrons. Such centres are, with a few exceptions in the world, lacking today. They can be designed to also produce beta- and Augeremitters of therapeutic interest. Furthermore, emerging satellite PET scanners will in the near future demand long-lived positron emitters for diagnostics with macromolecular radiopharmaceuticals, and these can also be produced at such centres. To secure continued development and to meet the foreseen requirements for radionuclide availability from the medical community it is necessary to establish specialized cyclotron centres for radionuclide production.

Targeted delivery of cisplatin to prostate cancer cells by aptamer functionalized Pt(IV) prodrug-PLGA-PEG nanoparticles

Cisplatin is used to treat a variety of tumors, but dose limiting toxicities or intrinsic and acquired resistance limit its application in many types of cancer including prostate. We report a unique strategy to deliver cisplatin to prostate cancer cells by constructing Pt(IV)-encapsulated prostate-specific membrane antigen (PSMA) targeted nanoparticles (NPs) of poly(D,L-lactic-co-glycolic acid) (PLGA)-poly(ethylene glycol) (PEG)-functionalized controlled release polymers. By using PLGA-b-PEG nanoparticles with PSMA targeting aptamers (Apt) on the surface as a vehicle for the platinum(IV) compound c,t,c-[Pt(NH(3))(2)(O(2)CCH(2)CH(2)CH(2)CH(2)CH(3))(2)Cl(2)] (1), a lethal dose of cisplatin was delivered specifically to prostate cancer cells. PSMA aptamer targeted delivery of Pt(IV) cargos to PSMA(+) LNCaP prostate cancer cells by endocytosis of the nanoparticle vehicles was demonstrated using fluorescence microscopy by colocalization of green fluorescent labeled cholesterol-encapsulated NPs and early endosome marker EEA-1. The choice of linear hexyl chains in 1 was the result of a systematic study to optimize encapsulation and controlled release from the polymer without compromising either feature. Release of cisplatin from the polymeric nanoparticles after reduction of 1 and formation of cisplatin 1,2-intrastrand d(GpG) cross-links on nuclear DNA was confirmed by using a monoclonal antibody for the adduct. A comparison between the cytotoxic activities of Pt(IV)-encapsulated PLGA-b-PEG NPs with the PSMA aptamer on the surface (Pt-NP-Apt), cisplatin, and the nontargeted Pt(IV)-encapsulated NPs (Pt-NP) against human prostate PSMA-overexpressing LNCaP and PSMA(-) PC3 cancer cells revealed significant differences. The effectiveness of PSMA targeted Pt-NP-Apt nanoparticles against the PSMA(+) LNCaP cells is approximately an order of magnitude greater than that of free cisplatin.

Management of asymptomatic rise in prostatic-specific antigen in patients with prostate cancer

Biochemical failure after curative-intent therapies is an increasingly common dilemma confronting patients and physicians. No definition of biochemical failure exists that can be applied to all forms of treatment and that is not to some degree affected by the follow-up interval, pretreatment prognostic factors, or the frequency of prostatic-specific antigen (PSA) testing. Available imaging techniques lack sensitivity in detection of occult micrometastases. Prognostic factors such as tumor characteristics and PSA kinetics should be considered when recommending second-line therapies. For those patients with suspected localized recurrence, second-line treatment with salvage therapies may provide long-term disease control. Hormonal therapy, although most commonly employed for PSA recurrence, is of palliative benefit only. Currently, the most appropriate therapeutic intervention for asymptomatic patients with evidence of biochemical failure remains undefined.

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.

Enhancing the utility of prostascint SPECT scans for patient management

This project investigated reducing the artifact content of In-ill ProstaScint SPECT scans for use in treatment planning and management. Forty-one patients who had undergone CT or MRI scans and simultaneous Tc-99m RBC/In-111 ProstaScint SPECT scans were included. SPECT volume sets, reconstructed using Ordered Set-Expectation Maximum (OS-EM) were compared against those reconstructed with standard Filtered Back projection (FBP). Bladder activity in Tc-99m scans was suppressed within an ellipsoidal volume. Tc-99m voxel values were subtracted from the corresponding In-111 after scaling based on peak activity within the descending aorta. The SPECT volume data sets were merged with the CT or MRI scans before and after processing. Volume merging, based both on visual assessment and statistical evaluation, was not affected. Thus iterative reconstruction together with bladder suppression and blood pool subtraction may improve the interpretation and utility of ProstaScint SPECT scans for patient management.

Postprostatectomy target-normal structure overlap volume differences using computed tomography and radioimmunoscintigraphy images for radiotherapy treatment planning

PURPOSE

The purpose of this study was to analyze regions of uptake in normal structures on postprostatectomy radioimmunoscintigraphy (RIS) images by evaluating differences in the overlap volumes of prostate fossa clinical target volume (CTV) and planning target volume (PTV) using correlative computed tomography (CT) images.

MATERIALS AND METHODS

The electronic records of 13 patients who received external beam radiotherapy postprostatectomy and who underwent a vessel-based RIS/CT registration were reviewed. For each patient, the RIS-defined CTV (CTV(RIS)) was compared (in terms of the overlap volume with the surrounding bladder, rectum, pubic symphysis, and penile bulb) with the CT-defined CTV(pre) before this registration and also with CTV(post) (the final target volume used for treatment). Similar analyses were done for PTV(RIS), PTV(pre), and PTV(post) defined in each case to be the corresponding CTV + 1-cm margin.

RESULTS

CTV(RIS) overlapped significantly more with the bladder, rectum, and symphysis, but not with the penile bulb, than did either the CTV(pre) or CTV(post). However, the corresponding PTV analyses revealed no significant differences between any of the overlap volumes of any of the PTVs with the bladder, rectum, and penile bulb, but did reveal a significant difference between the PTV(RIS) and PTV(post) overlap volumes with the symphysis compared with PTV(pre) overlap volumes with the symphysis.

CONCLUSIONS

On RIS images, there appear to be areas of uptake in the bladder, rectum, and pubic symphysis but not the penile bulb; however, the dosimetric consequences of this uptake for radiation treatment planning are minimal on the bladder, rectum, and penile bulb, but require segmentation for dose reduction to the pubic symphysis.

Update on magnetic resonance imaging, ProstaScint, and novel imaging in prostate cancer

PURPOSE OF REVIEW

Despite marked stage migration, approximately a third of patients with clinically organ-confined prostate cancer will have extracapsular extension on pathological analysis. To improve outcomes further, alternative modalities of determining extraprostatic disease must be investigated beyond the current clinical parameters of digital rectal examination, prostate-specific antigen, and Gleason score. In addition, discerning the location of tumor in patients with biochemical recurrence directly affects treatment choice. This review highlights developments in prostate cancer imaging that may improve staging and treatment planning for prostate cancer patients.

RECENT FINDINGS

Magnetic resonance imaging is most useful in the initial evaluation of men with prostate cancer. Its high specificity for the diagnosis of extracapsular extension is tempered by its low sensitivity. Positron emission tomography is used to assess regional and distant metastasis in many malignancies. Investigation into the most appropriate radiotracer for prostate cancer is paramount in any future applicability. The unique role of ProstaScint has been in evaluating patients with biochemical failure and in trying to discern metastasis before definitive therapy. The addition of spectroscopic imaging and nanoparticle infusion may lead to further improvements. Therefore, in differentiating local versus distant recurrence, appropriate interventions with radiotherapy or hormonal manipulation may be instituted.

SUMMARY

Magnetic resonance imaging, ProstaScint, and to some extent positron emission tomography are all relevant imaging modalities for the evaluation of patients with prostate cancer. Current technological advances in each arena are improving the accuracy of diagnosis. Despite their specific limitations, use in the proper clinical setting may provide essential information to improve management decisions and disease outcomes.

PSA relapse prostate cancer: the importance of tailored therapy

Prostate specific antigen (PSA) is an invaluable tumor marker in the detection of early prostate cancer as well as a predictor of recurrence after treatment of localized disease. Current practice entails the use of factors such as pretherapy grade, stage and PSA, PSA doubling time, nature of previous therapy and patient age and functional status for a treatment recommendation. For a PSA relapse post radical prostatectomy, radiation therapy to the prostatic fossa is a primary therapeutic consideration. With careful patient selection, about 30 to 40% of patients are rendered disease free using this approach. For patients with radiation therapy as the primary treatment for their prostate cancer, salvage prostatectomy can be considered, but is rarely feasible. Systemic therapy with hormones is standard if patients are not candidates for the above mentioned salvage local therapies or if they relapse after exhaustive local therapies. Unfortunately androgen suppressive therapy is unlikely to induce cure, or prolonged remissions in PSA relapse prostate cancer. The strategy of addition of chemotherapy or biologic therapy to androgen suppressive therapy is under active investigation. The goal of this therapy is to make an impact on the time to progression to metastatic prostate cancer and correspondingly decrease prostate cancer related mortality. Preliminary results of studies incorporating early chemotherapy in combination with androgen suppressive therapy are encouraging, with improvement in time to progression and overall survival. The evaluation of biologic agents and agents with better toxicity profiles is ongoing. This is very important to make therapy widely applicable and to enable prolonged administration especially in a disease such as prostate cancer with a relatively long natural history. Strategies of adjuvant and neoadjuvant therapy in locally advanced prostate cancer are exploring the possibility of reducing the chance of PSA relapse by treating micrometastatic disease. This review discusses the current practices in risk stratification and management of PSA relapse prostate cancer. It also highlights the major clinical trials and areas of active investigation in this field.

Variables in predicting survival based on treating "PSA-only" relapse

Prostate cancer recurrence (after prior local treatment) that is detectable only by a rise in serum prostate specific antigen (PSA) level is a very common problem facing clinicians. Given that the majority of contemporary era men with PSA-only or biochemical recurrence are relatively young and otherwise healthy, treatment requires approaches that both improve clinical outcomes and preserve quality of life. Treatment is in one of two broad categories, additional local therapies, termed "salvage" local therapy and systemic therapies. For radical prostatectomy patients, salvage external beam radiotherapy to the prostate bed is commonly employed, being reserved for early biochemical recurrence in men with low risk at distant metastases. For primary radiation patients, salvage radical prostatectomy or cryotherapy can similarly be used for those men felt not to harbor distant metastases. Systemic therapy generally involves hormonal therapy. Traditional hormonal therapy (orchiectomy, luteinizing hormone-releasing hormone agonists, or maximum androgen blockade) is the current mainstay of systemic treatment for biochemical recurrence, although nontraditional approaches, such as antiandrogen monotherapy, are increasingly being used. Variables in predicting survival based on treating PSA relapse is problematic. The condition of biochemical failure has only been recognized in the last decade and few "PSA-era" patients with biochemical recurrence have actually died of disease. Hence, the validation of prediction variables in this setting is just emerging. Early work would suggest that timing of recurrence, Gleason grade, and PSA velocity or doubling time during relapse are important prognostic factors. New data on PSA doubling time will be presented.

99mTechnetium-C595 radioimmunoscintigraphy: a potential staging tool for bladder cancer

OBJECTIVES

To assess whether immunoscintigraphy using a conjugate of the anti-MUC1 monoclonal antibody C595 and 99mTc could be used to target transitional cell bladder cancer after intravenous administration to patients.

PATIENTS AND METHODS

Twenty-one patients with invasive or metastatic transitional cell carcinoma were recruited. Patients received 1 mg of C595 labelled with 800 MBq 99mTc followed by imaging at 0.5, 6 and 24 h using a combination of planar and single-photon emission computed tomography. Of these patients, 14 subsequently underwent cystectomy, four underwent radiotherapy and the remaining three had histologically confirmed metastatic disease. The results of immunoscintigraphy were compared with surgical findings and conventional radiology.

RESULTS

There were no adverse reactions in any patient. Of the 20 patients who were found to have tumour at the time of the study, positive localization of antibody in tumour was apparent in 16. Of the remaining four patients, false-positive localization of antibody in presumed nodal tissue was detected in two. The remaining scan results were equivocal. In three patients, histologically confirmed pelvic nodal metastases that had not been detected on preoperative computed tomography were identified.

CONCLUSION

These early results show the potential of 99mTc-C595 immunoscintigraphy for staging bladder cancer. A larger study is needed to fully evaluate the technique.