Advances in targeted alpha therapy for prostate cancer

Amongst therapeutic radiopharmaceuticals, targeted alpha therapy (TαT) can deliver potent and local radiation selectively to cancer cells as well as the tumor microenvironment and thereby control cancer while minimizing toxicity. In this review, we discuss the history, progress, and future potential of TαT in the treatment of prostate cancer, including dosimetry-individualized treatment planning, combinations with small-molecule therapies, and conjugation to molecules directed against antigens expressed by prostate cancer cells, such as prostate-specific membrane antigen (PSMA) or components of the tumor microenvironment. A clinical proof of concept that TαT is efficacious in treating bone-metastatic castration-resistant prostate cancer has been demonstrated by radium-223 via improved overall survival and long-term safety/tolerability in the phase III ALSYMPCA trial. Dosimetry calculation and pharmacokinetic measurements of TαT provide the potential for optimization and individualized treatment planning for a precision medicine-based cancer management paradigm. The ability to combine TαTs with other agents, including chemotherapy, androgen receptor-targeting agents, DNA repair inhibitors, and immuno-oncology agents, is under investigation. Currently, TαTs that specifically target prostate cancer cells expressing PSMA represents a promising therapeutic approach. Both PSMA-targeted actinium-225 and thorium-227 conjugates are under investigation. The described clinical benefit, safety and tolerability of radium-223 and the recent progress in TαT trial development suggest that TαT occupies an important new role in prostate cancer treatment. Ongoing studies with newer dosimetry methods, PSMA targeting, and novel approaches to combination therapies should expand the utility of TαT in prostate cancer treatment.

123I-mIBG scintigraphy in neuroblastoma: development of a SIOPEN semi-quantitative reporting ,method by an international panel

Purpose

A robust method is required to standardise objective reporting of diagnostic ¹²³I-mIBG images in neuroblastoma. Prerequisites for an appropriate system are low inter- and intra-observer error and reproducibility across a broad disease spectrum. We present a new reporting method, developed and tested for SIOPEN by an international expert panel.

Method

Patterns of abnormal skeletal ¹²³I-mIBG uptake were defined and assigned numerical scores [0–6] based on disease extent within 12 body segments. Uptake intensity was excluded from the analysis. Data sets from 82 patients were scored independently by six experienced specialists as unblinded pairs (pre- and post-induction chemotherapy) and in random order as a blinded study. Response was defined as ≥50 % reduction in post induction score compared with baseline.

Results

In total, 1968 image sets were reviewed individually. Response rates of 88 % and 82 % were recorded for patients with baseline skeletal scores ≤23 and 24-48 respectively, compared with 44 % response in patients with skeletal scores >48 (p = 0.02). Reducing the number of segments or extension scale had a small but statistically negative impact upon the number of responses detected. Intraclass correlation coefficients [ICCs] calculated for the unblinded and blinded study were 0.95 at diagnosis and 0.98 and 0.99 post-induction chemotherapy, respectively.

Conclusions

The SIOPEN mIBG score method is reproducible across the full spectrum of disease in high risk neuroblastoma. Numerical assessment of skeletal disease extent avoids subjective evaluation of uptake intensity. This robust approach provides a reliable means with which to examine the role of 123I mIBG scintigraphy as a prognostic indicator in neuroblastoma.

Guidelines for the management of gastroenteropancreatic neuroendocrine (including carcinoid) tumours (NETs)

These guidelines update previous guidance published in 2005. They have been revised by a group who are members of the UK and Ireland Neuroendocrine Tumour Society with endorsement from the clinical committees of the British Society of Gastroenterology, the Society for Endocrinology, the Association of Surgeons of Great Britain and Ireland (and its Surgical Specialty Associations), the British Society of Gastrointestinal and Abdominal Radiology and others. The authorship represents leaders of the various groups in the UK and Ireland Neuroendocrine Tumour Society, but a large amount of work has been carried out by other specialists, many of whom attended a guidelines conference in May 2009. We have attempted to represent this work in the acknowledgements section. Over the past few years, there have been advances in the management of neuroendocrine tumours, which have included clearer characterisation, more specific and therapeutically relevant diagnosis, and improved treatments. However, there remain few randomised trials in the field and the disease is uncommon, hence all evidence must be considered weak in comparison with other more common cancers.

Dynamic contrast-enhanced MRI of neuroendocrine hepatic metastases: A feasibility study using a dual-input two-compartment model

Neuroendocrine hepatic metastases exhibit various contrast uptake enhancement patterns in dynamic contrast-enhanced MRI. Using a dual-input two-compartment distributed parameter model, we analyzed the dynamic contrast-enhanced MRI datasets of seven patient study cases with the aim to relate the tumor contrast uptake patterns to parameters of tumor microvasculature. Simulation studies were also performed to provide further insights into the effects of individual microcirculatory parameter on the tumor concentration-time curves. Although the tumor contrast uptake patterns can be influenced by many parameters, initial results indicate that hepatic blood flow and the ratio of fractional vascular volume to fractional interstitial volume may potentially distinguish between the patterns of neuroendocrine hepatic metastases.

Criteria for evaluation of disease extent by (123)I-metaiodobenzylguanidine scans in neuroblastoma: a report for the International Neuroblastoma Risk Group (INRG) Task Force

BACKGROUND

Neuroblastoma is an embryonic tumour of the sympathetic nervous system, metastatic in half of the patients at diagnosis, with a high preponderance of osteomedullary disease, making accurate evaluation of metastatic sites and response to therapy challenging. Metaiodobenzylguanidine (mIBG), taken into cells via the norepinephrine transporter, provides a sensitive and specific method of assessing tumour in both soft tissue and bone sites. The goal of this report was to develop consensus guidelines for the use of mIBG scans in staging, response assessment and surveillance in neuroblastoma.

METHODS

The International Neuroblastoma Risk Group (INRG) Task Force, including a multidisciplinary group in paediatric oncology of North and South America, Europe, Oceania and Asia, formed a subcommittee on metastatic disease evaluation, including expert nuclear medicine physicians and oncologists, who developed these guidelines based on their experience and the medical literature, with approval by the larger INRG Task Force.

RESULTS

Guidelines for patient preparation, radiotracer administration, techniques of scanning including timing, energy, specific views, and use of single photon emission computed tomography are included. Optimal timing of scans in relation to therapy and for surveillance is reviewed. Validated semi-quantitative scoring methods in current use are reviewed, with recommendations for use in prognosis and response evaluation.

CONCLUSIONS

Metaiodobenzylguanidine scans are the most sensitive and specific method of staging and response evaluation in neuroblastoma, particularly when used with a semi-quantitative scoring method. Use of the optimal techniques for mIBG in staging and response, including a semi-quantitative score, is essential for evaluation of the efficacy of new therapy.

The use of 18F-FDG PET/CT in colorectal liver metastases--comparison with CT and liver MRI

PURPOSE

We compared 18-fluoro-2-deoxyglucose ((18)F-FDG) positron emission tomography-CT (PETCT) with contrast-enhanced whole-body CT (ceCT) in identifying extrahepatic disease and with manganese dipyridoxyl diphosphate (Mn-DPDP) liver MRI for liver metastases in patients with colorectal liver metastases being considered for surgery.

METHODS

Sixty-five patients (median age 65 years; 42 men) with colorectal cancer and known or suspicious liver metastases and who underwent a PETCT, ceCT and Mn-DPDP MRI were identified. Results were retrospectively reviewed for extrahepatic disease on PETCT and ceCT, and for the presence and number of liver metastases on PETCT and Mn-DPDP MRI. Proof of metastases was based on histopathology or clinical/imaging follow-up, demonstrating disease progression or response.

RESULTS

PETCT identified unexpected extrahepatic disease not detected on ceCT, leading to change in surgical management in 17%. There were three other false-positive cases on PETCT. For liver metastases on a per-patient basis, the sensitivity and specificity of both PETCT and Mn-DPDP MRI were 98% and 100%, respectively. On a per-lesion basis, PETCT and MRI were discordant in 15% (10/66 scans). MRI correctly identified more sub-centimeter metastases in eight scans. PETCT correctly identified more metastases in one case and confirmed disease in one equivocal MRI.

CONCLUSION

PETCT has incremental benefit over conventional ceCT in identifying extrahepatic disease in metastatic colorectal cancer. PETCT has high sensitivity and specificity for the presence of liver metastases and should be included early in initial pre-surgical evaluation and could potentially guide the use of Mn-DPDP MRI. However, Mn-DPDP MRI is superior for small liver metastases and remains a prerequisite for surgical planning in patients with confined liver metastases.

Report of a European consensus workshop to develop recommendations for the optimal use of 90Y-ibritumomab tiuxetan (Zevalin®) in lymphoma

BACKGROUND

Non-Hodgkin's lymphoma (NHL) comprises a group of related haematological malignancies, predominantly of B-cell origin, which have been described as indolent or aggressive according to their clinical course. Standard treatment for indolent NHL consists of conventional chemotherapy, but, although long-term remissions may occur, most patients will die of their disease. Radioimmunotherapy (RIT) is a novel modality for treating indolent NHL, using monoclonal antibodies to target tumour cells with systemic, low-dose radiation. (90)Y-Ibritumomab tiuxetan (Zevalin); Schering AG, Berlin, Germany), the first RIT approved for use in relapsed/refractory indolent NHL, comprises the murine anti-CD20 monoclonal antibody ibritumomab, covalently linked to the high-energy beta-emitter, yttrium-90, by the chelator, tiuxetan.

MATERIALS AND METHODS

A multidisciplinary consensus workshop of European clinicians who had taken part in clinical trials of (90)Y-ibritumomab tiuxetan was convened to develop recommendations for the clinical preparation and administration of (90)Y-ibritumomab tiuxetan in Europe. The workshop was held in anticipation of European Medicines Agency approval of this agent, which was gained in 2004 for adult patients with rituximab-relapsed or refractory CD20(+) follicular B-cell NHL.

RESULTS AND CONCLUSIONS

This article summarises the consensus recommendations developed for hemato-oncologists.

A survey of the role of the UK physicist in nuclear medicine: a report of a joint working group of the British Institute of Radiology, British Nuclear Medicine Society, and the Institute of Physics and Engineering in Medicine

Guidelines for the provision of physics support to nuclear medicine were published in 1999 by a joint working group of the British Institute of Radiology, the British Nuclear Medicine Society, and the Institute of Physics and Engineering in Medicine. Following publication of the guidelines, a survey was conducted by the working group to gather data on the actual level of physicist support in UK hospitals of different types and on the activities undertaken by physicists. The data were collected in the 12 months following the publication of guidelines and cover different hospital models and seven UK regions. The results provide evidence that many of the smaller units - small teaching hospitals and, particularly, small district general hospitals - have insufficient physics support. Although, on average, there is good agreement between the guidelines and the survey data for medium and large district general hospitals, there is wide variation in the level of physics provision between hospitals delivering apparently similar services. This emphasizes the need for national guidelines, against which institutions may be bench-marked and which may be used as a recommendation for the staffing levels necessary to ensure services are delivered safely and standards are not compromised. The complexity and variety of workload is an important factor in determining the level of physics support. As services develop, it is vital that this aspect is recognized to ensure that appropriate resources are available for the required physics input, even if any new service represents only a modest clinical throughput in terms of patient numbers.

Intrapulmonary arteriovenous shunting may be a universal phenomenon in patients with the superior cavopulmonary anastomosis: a radionuclide study

OBJECTIVE

To evaluate the extent of intrapulmonary right to left shunting in children after bidirectional cavopulmonary anastomosis (BCPA).

DESIGN

Prospective study of patients who underwent BCPA in a single centre.

PATIENTS

17 patients with complex cyanotic congenital cardiac malformations who underwent BCPA at 1-45 months of age (median 21 months) were evaluated 15-64 months postoperatively (median 32 months). Five children between 1 and 10 years (median 5 years) with normal or surgically corrected intracardiac anatomy and peripheral pulmonary circulation who required V/Q scanning for other reasons were used as controls.

INTERVENTIONS

All patients underwent cardiac catheterisation to exclude angiographically demonstrable venovenous collaterals followed by pulmonary perfusion scanning using (99m)technetium ((99m)Tc) labelled albumen microspheres to quantify the intrapulmonary right to left shunt.

MAIN OUTCOME MEASURE

Percentage of intrapulmonary right to left shunt.

RESULTS

The mean (SD) level of physiological right to left shunting found in the control group was 5.4 (2.3)%. All patients with BCPA showed the presence of a significantly higher level of intrapulmonary shunting (26.8 (16.9)%, p < 0.001). The degree of shunting was significantly increased in the subgroup of 11 patients with BCPA as the only source of pulmonary blood flow (34.9 (15.8)%), when compared to the six remaining patients with an additional source of pulmonary blood supply (12.0 (2.6)%, p < 0.001). There was a negative correlation between age at BCPA and the shunt percentage found in the patients with a competitive source of pulmonary blood flow (r = -0.63, p < 0. 01).

CONCLUSIONS

Intrapulmonary right to left shunting develops in all patients following BCPA. This may be caused by a sustained and inappropriate vasodilatation resulting from absence or decreased levels of a substance that inhibits pulmonary vasodilatation. Augmenting BCPA with an additional source of blood flow containing hepatic factor limits the degree of intrapulmonary arteriovenous shunting and may help provide successful longer term palliation.

Lower moiety heminephroureterectomy in the duplex refluxing kidney: the accuracy of isotopic scintigraphy in functional assessment

OBJECTIVE

To determine the accuracy of dimercaptosuccinic acid (DMSA) scintigraphy in assessing the differential function between upper and lower moieties of a refluxing duplex system.

PATIENTS AND METHODS

Between 1990 and 1996, 20 patients underwent lower moiety heminephroureterectomy. All patients had their differential renal function assessed by DMSA scintigraphy before and after surgery, the results being assessed by comparing the predicted and actual loss of renal function.

RESULTS

The mean (SD, range) function attributed to the scarred lower moiety (predicted loss of function) was 4.3 (4.9, 0-14)%, which compared with an actual mean loss of function of 6.8 (5.1, +4 to -16)%. Thus the mean (SD, range) difference between the predicted and actual loss of renal function was -2.1 (3.2, +4 to -8)%.

CONCLUSION

DMSA scintigraphy provides an accurate assessment of the differential renal function between upper and lower moieties in a duplex system. The decision to proceed to lower moiety heminephroureterectomy can be logically based on the information gained from DMSA scintigraphy.

Pulmonary embolism. Is the clinical history a useful adjunct to aid the interpretation of the equivocal lung scan?

Pulmonary embolism is commonly fatal, yet notoriously difficult to detect. Diagnosis often relies on the ventilation-perfusion radionuclide scan, which itself is frequently equivocal. It has been suggested that if the equivocal ventilation-perfusion scan is interpreted in the light of clinical information, diagnostic accuracy can be improved. However, which features in the history should be considered? In this study of 197 patients undergoing ventilation-perfusion scanning, the clinical data of the 98 patients with either high-probability or normal scans were compared to the scan findings. The presence of a deep vein thrombosis was significantly associated with a high probability scan, whereas the presence of constant chest pain was significantly associated with a negative scan. Classical symptoms for pulmonary embolism, namely pleuritic chest pain and hemoptysis, were poor predictors of high-probability scans. Consequently, the authors advise considerable caution when using the clinical data to aid the interpretation of the equivocal lung scan in the individual case.

Late functional results after surgical closure of acquired ventricular septal defect

To assess the longer term outlook for patients who have undergone surgery for acquired (postinfarction) ventricular septal defect, we interviewed and studied 60 survivors from a single regional cardiac center between 3 and 144 months after the operation. Including the patients who died within 1 month of the operation, the 5-, 10-, and 14-year survivals (with standard errors) were 69% (65% to 74%), 50% (44% to 57%), and 37% (27% to 46%). Eighty-two percent of patients were in New York Heart Association class I or II. Ten patients (17%) had a persisting but not hemodynamically significant ventricular septal defect. Mean left ventricular ejection fraction was reduced at 0.39 (standard deviation 0.15), but this did not correlate with either New York Heart Association class or exercise tolerance. Twenty-eight patients (47%) had asymptomatic arrhythmias (17 with ventricular premature beats). Angina and other medical problems were not prevalent.