The impact of positron emission tomography (PET) on expected management during cancer treatment

Development of a hypoxia-activated red-emission fluorescent probe for in vivo tumor microenvironment imaging and anti-tumor therapy

Hypoxia, a significant feature of the tumor microenvironment, is closely associated with tumor growth, metastasis, and drug resistance. In the field of tumor microenvironment analysis, accurately imaging and quantifying hypoxia - a critical factor associated with tumor progression, metastasis, and resistance to therapy - remains a significant challenge. Herein, a hypoxia-activated red-emission fluorescent probe, ODP, for in vivo imaging of hypoxia in the tumor microenvironment is presented. Among various imaging methods, optical imaging is particularly convenient due to its rapid response and high sensitivity. The ODP probe specifically targets nitroreductase (AzoR), an enzyme highly expressed in hypoxic cells, playing a vital role by catalyzing the cleavage of azo bonds. The optical properties of ODP exhibited excellent performance in terms of fluorescence enhancement, fluorescence lifetime (0.81 ns), and detection limit (0.86 µM) in response to SDT. Cell imaging experiments showed that ODP could effectively detect and image intracellular hypoxia and the imaging capability of ODP was studied under various conditions including cell migration, antioxidant treatment, and different incubation times. Through comprehensive in vitro and in vivo experiments, including cellular imaging and mouse tumor models, this work demonstrates the efficacy of ODP in accurately detecting and imaging hypoxia. Moreover, ODP's potential in inducing apoptosis in cancer cells offers a promising avenue for integrating diagnostic and therapeutic strategies in cancer treatment. This innovative approach not only contributes to the understanding and assessment of tumor hypoxia but also opens new possibilities for targeted cancer therapy.

The impact of staging FDG-PET/CT on treatment for stage III NSCLC - an analysis of population-based data from Ontario, Canada

Purpose

Fluoro-2-deoxyglucose positron-emission tomography (FDG-PET/CT) is now considered a standard investigation for the staging of new cases of stage III NSCLC. However, there is not published level 3 evidence demonstrating the impact of FDG-PET/CT on appropriate therapy in this setting. Using retrospective population-based data, we sought to examine the role and timing that FDG-PET/CT scans play in influencing treatment choice, as well as survival in patients diagnosed with stage III NSCLC.

Materials and methods

A retrospective cohort of patients diagnosed with stage III NSCLC from 2009-2017 in Ontario were identified from the IC/ES (formerly Institute of Clinical Evaluative Sciences) database. FDG-PET/CT utilization over time, trends in mediastinal biopsy technique and usage, the impact of FDG-PET/CT on overall survival (OS), and its influence on use of concurrent chemoradiotherapy (CRT) were explored. The impact of timing of pre-treatment FDG-PET/CT on OS was also analyzed (≤28 days prior to treatment, 29-56 days prior, and >56 days prior).

Results

Between 2007 and 2017, a total of 13 796 people were diagnosed with stage III NSCLC in Ontario. FDG-PET/CT utilization increased over time with 0% of cases in 2007 and 74% in 2017 with pre-treatment FDG-PET/CT scans. The number of patients who received a mediastinal biopsy similarly increased in this timeframe increasing from 41% to 53%. More patients with pre-treatment FDG-PET/CT scans received curative-intent therapy than those who did not: 23% vs 13% for CRT (p<0.001), and 23% vs 10% for surgery (p<0.001). Median OS was longer in those with FDG-PET/CT scans prior to treatment (17 vs 11 months), as was 5-year survival (22% vs 14%, p<0.001), and this held true on both univariate and multivariate analyses. Timing of FDG-PET/CT scan relative to treatment was not associated with differences in OS.

Conclusion

Improvements in OS were seen in this cohort of stage III NSCLC patients who underwent a pre-treatment FDG-PET/CT scan. This can likely be attributed to stage-appropriate therapy due to more complete staging using FDG-PET/CT. This study stresses the importance of complete staging for suspected stage III NSCLC using FDG-PET/CT, and a need for continued advocacy for increased access to FDG-PET/CT scans.

The changing landscape of nuclear medicine and a new era: the "NEW (Nu) CLEAR Medicine": a framework for the future

Nuclear Medicine is witnessing a revolution across a large spectrum of patient care applications, hardware, software and novel radiopharmaceuticals. We propose to offer a framework of the nuclear medicine practice of the future that incorporates multiple novelties and coined as the NEW (nu) Clear medicine. All these new developments offer a significant clarity and real clinical impact, and we need a concerted effort from all stakeholders in the field for bedside implementation and success.

Advanced Imaging for Detection of Foci of Infection in Staphylococcus aureus Bacteremia- Can a Scan Save Lives?

Bloodstream infection or sepsis is a common cause of mortality globally. Staphylococcus aureus (S. aureus) is of particular concern, through its ability to seed metastatic infections in almost any organ after entering the bloodstream (S. aureus bacteraemia), often without localising signs. A positive blood culture for S. aureus bacteria should lead to immediate and urgent identification of the cause. Failure to detect a precise focus of infection is associated with higher mortality, sometimes despite appropriate antibiotics. This is likely due to the limited ability to effectively target therapy in occult lesions. Early detection of foci of metastatic S. aureus infection is therefore key for optimal diagnosis and subsequent therapeutic management. 18F-FDG-PET/CT and MRI offer us invaluable tools in the localisation of foci of S. aureus infection. Crucially, they may identify unexpected foci at previously unsuspected locations in the body, for example vertebral osteomyelitis in the absence of back pain. S. aureus bloodstream infections are further complicated by their microbiological recurrence; 18F-FDG-PET/CT provide a means of localising, thus enabling source control. More evidence is emerging as to the utility of 18F-FDG-PET/CT in this setting, perhaps even to the point of reducing mortality. 18 F-FDG-PET/MRI may have a similar impact. The available evidence demonstrates a need to investigate the impact of 18F-FDG-PET/CT and MRI scanning in clinical management and outcomes of S. aureus infection further in a randomised prospective clinical trial.

Screening for Colorectal Cancer Leading into a New Decade: The "Roaring '20s" for Epigenetic Biomarkers?

Colorectal cancer (CRC) has an important bearing (top five) on cancer incidence and mortality in the world. The etiology of sporadic CRC is related to the accumulation of genetic and epigenetic alterations that result in the appearance of cancer hallmarks such as abnormal proliferation, evasion of immune destruction, resistance to apoptosis, replicative immortality, and others, contributing to cancer promotion, invasion, and metastasis. It is estimated that, each year, at least four million people are diagnosed with CRC in the world. Depending on CRC staging at diagnosis, many of these patients die, as CRC is in the top four causes of cancer death in the world. New and improved screening tests for CRC are needed to detect the disease at an early stage and adopt patient management strategies to decrease the death toll. The three pillars of CRC screening are endoscopy, radiological imaging, and molecular assays. Endoscopic procedures comprise traditional colonoscopy, and more recently, capsule-based endoscopy. The main imaging modality remains Computed Tomography (CT) of the colon. Molecular approaches continue to grow in the diversity of biomarkers and the sophistication of the technologies deployed to detect them. What started with simple fecal occult blood tests has expanded to an armamentarium, including mutation detection and identification of aberrant epigenetic signatures known to be oncogenic. Biomarker-based screening methods have critical advantages and are likely to eclipse the classical modalities of imaging and endoscopy in the future. For example, imaging methods are costly and require highly specialized medical personnel. In the case of endoscopy, their invasiveness limits compliance from large swaths of the population, especially those with average CRC risk. Beyond mere discomfort and fear, there are legitimate iatrogenic concerns associated with endoscopy. The risks of perforation and infection make endoscopy best suited for a confirmatory role in cases where there are positive results from other diagnostic tests. Biomarker-based screening methods are largely non-invasive and are growing in scope. Epigenetic biomarkers, in particular, can be detected in feces and blood, are less invasive to the average-risk patient, detect early-stage CRC, and have a demonstrably superior patient follow-up. Given the heterogeneity of CRC as it evolves, optimal screening may require a battery of blood and stool tests, where each can leverage different pathways perturbed during carcinogenesis. What follows is a comprehensive, systematic review of the literature pertaining to the screening and diagnostic protocols used in CRC. Relevant articles were retrieved from the PubMed database using keywords including: "Screening", "Diagnosis", and "Biomarkers for CRC". American and European clinical trials in progress were included as well.

EANM guideline on the role of 2-[18F]FDG PET/CT in diagnosis, staging, prognostic value, therapy assessment and restaging of ovarian cancer, endorsed by the American College of Nuclear Medicine (ACNM), the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the International Atomic Energy Agency (IAEA)

In most patients with ovarian carcinoma, the diagnosis is reached when the disease is long past the initial stages, presenting already an advanced stage, and they usually have a very bad prognosis. Cytoreductive or debulking surgical procedures, platinum-based chemotherapy and targeted agents are key therapeutic elements. However, around 7 out of 10 patients present recurrent disease within 36 months from the initial diagnosis. The metastatic spread in ovarian cancer follows three pathways: contiguous dissemination across the peritoneum, dissemination through the lymphatic drainage and, although less importantly in this case, through the bloodstream. Radiological imaging, including ultrasound, CT and MRI, are the main imaging techniques in which management decisions are supported, CT being considered the best available technique for presurgical evaluation and staging purposes. Regarding 2-[¹⁸F]FDG PET/CT, the evidence available in the literature demonstrates efficacy in primary detection, disease staging and establishing the prognosis and especially for relapse detection. There is limited evidence when considering the evaluation of therapeutic response. This guideline summarizes the level of evidence and grade of recommendation for the clinical indications of 2-[¹⁸F]FDG PET/CT in each disease stage of ovarian carcinoma.

Influence of X-ray computed tomography (CT) exposure and reconstruction parameters on positron emission tomography (PET) quantitation

Background

The CT of PET CT provides diagnostic information, anatomic localisation and attenuation correction (AC). When only AC is required, very lose dose CT is desirable. CT iterative reconstruction (IR) improves image quality with lower exposures however there is little data on very low dose IR CT for AC of PET. This work assesses the impact of CT exposure and reconstruction algorithm on PET voxel values.

Method

An anthropomorphic torso phantom was filled with physiologically typical [18]F concentrations in heart, liver and background compartments. A 17-mm-diameter right lung “tumour” filled with [18]F was included (surrounding lung contained no 18[F]). PET was acquired followed by 24 CT acquisitions with varying CT exposures (15–50 mAs, 80–120 kVp, pitch 0.671 or 0.828). Each CT was reconstructed twice using filtered back projection (FBP) or IR and these used for AC of PET. The reference PET reconstruction (RR) used CT acquired at 50 mAs, 120 kVp, pitch 0.828, IR, all others were test PET reconstructions (TR). Regions of interest (ROIs) were drawn in the liver, soft tissue and over “tumour” on each TR and compared with the RR. Voxel values in each TR were compared to the RR using a paired t test and by calculating which and what proportion of voxels in each TR differed by a quantitatively significant difference (QSD) from the RR.

Results

TRs reconstructed using lower dose CTs underestimated mean and maximum ROI activity relative to the RR; greater with IR than FBP. Once CT dose index (CTDI) increased to 1 mGy, differences were less than QSD. On voxel analysis, all TRs were significantly different to the RR (p < 0.0001). TRs reconstructed at the lowest CT exposure with IR had 6% of voxels that differed by greater than QSD. Differences were reduced with increasing CTDI and FBP reconstruction. Voxels which exceeded the QSD were spatially localised to regions of high activity, interfaces between different attenuation and areas of CT beam hardening.

Conclusions

Very low dose CT exposures are feasible for accurate PET AC. Scanner- and reconstruction-specific validation should be employed prior very low dose CT AC for PET.

Clinical implication of myocardial FDG uptake pattern in oncologic PET: retrospective comparison study with stress myocardial perfusion imaging as the reference standard

OBJECTIVE

The purpose of this study was to determine the clinical implication of the myocardial FDG uptake patterns by comparing with the results of stress myocardial perfusion imaging (MPI) as the reference standard.

METHODS

By reviewing the medical records, 86 pairs of stress MPI and FDG PET/CT of 84 patients who underwent stress MPI and oncologic FDG PET/CT in 1 month were included in this study. The patterns of the myocardial FDG uptake were classified into five patterns such as 'low', 'diffuse', 'basal ring', 'focal high', and 'focal defect on diffuse high'. MPI was evaluated using a 5-point scoring model ranging from 0 (normal uptake) to 4 (uptake absent) based on the 17-segment model. The summed stress score of 4 or higher was defined as 'abnormal MPI'. Factors predictive of abnormal MPI were analyzed using a log-rank multivariate test and p < 0.05 was set as significant.

RESULTS

Abnormal MPI was observed in only 16 of 36 (44%) patients with 'low' pattern, 10 of 23 (43%) patients with 'diffuse high' pattern, and 1 of 9 (11%) patients with 'basal ring' pattern, but in 8 of 9 (89%) patients with 'focal high' pattern, and 8 of 9 (89%) patients with 'focal defect on diffuse high' pattern. The log-rank multivariate test revealed that 'focal high' and 'focal defect on diffuse high' pattern were correlated with an abnormal MPI.

CONCLUSIONS

These results indicate that further cardiac work-up might be helpful in the patients with 'focal high' pattern or 'focal defect on diffuse high' pattern of myocardial FDG at oncologic PET. A prospective study should be needed to further support this conclusion.

Vitamin E-inspired multi-scale imaging agent

The production and use of multi-modal imaging agents is on the rise. The vast majority of these imaging agents are limited to a single length scale for the agent (e.g. tissues only), which is typically at the organ or tissue scale. This work explores the synthesis of such an imaging agent and discusses the applications of our vitamin E-inspired multi-modal and multi-length scale imaging agents TB-Toc ((S,E)-5,5-difluoro-7-(2-(5-((6-hydroxy-2,5,7,8-tetramethylchroman-2-yl) methyl) thiophen-2-yl) vinyl)-9-methyl-5H-dipyrrolo-[1,2-c:2',1'-f][1,3,2]diazaborinin-4-ium-5-uide). We investigate the toxicity of TB-Toc along with the starting materials and lipid based delivery vehicle in mouse myoblasts and fibroblasts. Further we investigate the uptake of TB-Toc delivered to cultured cells in both solvent and liposomes. TB-Toc has low toxicity, and no change in cell viability was observed up to concentrations of 10 mM. TB-Toc shows time-dependent cellular uptake that is complete in about 30 min. This work is the first step in demonstrating our vitamin E derivatives are viable multi-modal and length scale diagnostic tools.

Quantification of Cerenkov Luminescence Imaging (CLI) Comparable With 3-D PET Standard Measurements

Cerenkov luminescence imaging (CLI) is commonly performed using two-dimensional (2-D) conventional optical imaging systems for its cost-effective solution. However, quantification of CLI comparable to conventional three-dimensional positron emission tomography (PET) is challenging using these systems due to both the high attenuation of Cerenkov radiation (CR) on mouse tissue and nonexisting depth resolution of CLI using 2-D imaging systems (2-D CLI). In this study, we developed a model that estimates effective tissue attenuation coefficient and corrects the tissue attenuation of CLI signal intensity independent of tissue depth and size. To evaluate this model, we used several thin slices of ham as a phantom and placed a radionuclide (⁸⁹Zr and ⁶⁴Cu) inside the phantom at different tissue depths and sizes (2, 7, and 12 mm). We performed 2-D CLI and MicroPET/CT (Combined small animal PET and Computed Tomography (CT)) imaging of the phantom and in vivo mouse model after administration of ⁸⁹Zr tracer. Estimates of the effective tissue attenuation coefficient (μ_eff) for ⁸⁹Zr and ⁶⁴Cu were ∼2.4 and ∼2.6 cm⁻¹, respectively. The computed unit conversion factor to %ID/g from 2-D CLI signal was 2.74 × 10⁻³ μCi/radiance estimated from phantom study. After applying tissue attenuation correction and unit conversion to the in vivo animal study, an average quantification difference of 10% for spleen and 35% for liver was obtained compared to PET measurements. The proposed model provides comparable quantification accuracy to standard PET system independent of deep tissue CLI signal attenuation.

The Prognostic Value of 18F-FDG PET/CT in Monitoring Chemotherapy in Ovarian Cancer Both at Initial Diagnosis and at Recurrent Disease

Published experiences related to the prognostic relevance of negative or positive FDG PET/CT in patients treated for ovarian cancer for progression-free survival and overall survival are typically heterogeneous retrospective analyses. Several points have been well defined, these are as follows: (a) there is a correlation between FDG tumor uptake and prognosis; (b) ovarian cancer patients treated by neoadjuvant or adjuvant chemotherapy can be divided into responders with reduction in tumor FDG uptake during and after treatment and nonresponders where tumor FDG uptake remains stable or increases after treatment;

Preclinical Antiviral Testing for Dengue Virus Infection in Mouse Models and Its Association with Clinical Studies

At present, there is no licensed antiviral drug against dengue virus (DENV) infection. Mouse models of DENV infection have been widely used for preclinical evaluation of antivirals. However, only in a few instances so far have the data obtained from preclinical mouse model testing been associated with data from clinical studies in humans. In this Review, we focus on the antiviral drugs targeting viral replication that have been tested in animals/humans and discuss how preclinical drug evaluation in suitable mouse/animal models may be more fruitfully used to inform early phase clinical testing.

Fludeoxyglucose F 18 PET/CT Assessment of Ovarian Cancer

Ovarian cancer is one of the most common gynecologic cancers and one of the leading causes of cancer death in women. It is often asymptomatic in early stages, and thus most patients are diagnosed when it is of advanced stage. For these reasons, the role of biomarkers and tomographic imaging is crucial. Fludeoxyglucose F 18 PET/CT is a useful imaging modality in different clinical settings of the disease, overcoming some limits of conventional imaging and influencing prognosis and therapeutic approaches. PET/MR imaging is an emerging modality, and its potential role remains to be explored.

Hospice Admission and Survival After 18F-Fluoride PET Performed for Evaluation of Osseous Metastatic Disease in the National Oncologic PET Registry

We have previously reported that PET using ¹⁸F-fluoride (NaF PET) for assessment of osseous metastatic disease was associated with substantial changes in intended management in Medicare beneficiaries participating in the National Oncologic PET Registry (NOPR). Here, we use Medicare administrative data to examine the association between NaF PET results and hospice claims within 180 d and 1-y survival. Methods: We classified NOPR NaF PET results linked to Medicare claims by imaging indication (initial staging [IS]; detection of suspected first osseous metastasis [FOM]; suspected progression of osseous metastasis [POM]; or treatment monitoring [TM]) and type of cancer (prostate, lung, breast, or other). Results were classified as definitely positive scan findings versus probably positive scan findings versus negative scan findings for osseous metastasis for IS and FOM; more extensive disease versus no change or less extensive disease for POM; and worse prognosis versus no change or better prognosis for TM, based on the postscan assessment. Our study included 21,167 scans obtained from 2011 to 2014 of consenting NOPR participants aged 65 y or older. Results: The relative risk of hospice claims within 180 d of a NaF PET scan was 2.0-7.5 times higher for patients with evidence of new or progressing osseous metastasis than for those without, depending on indication and cancer type (all P < 0.008). The percentage difference in hospice claims for those with a finding of new or more advanced osseous disease ranged from 3.9% for IS prostate patients to 28% for FOM lung patients. Six-month survival was also associated with evidence of new or increased osseous disease; risk of death was 1.8-5.1 times as likely (all P ≤ 0.0001), with percentage differences of approximately 30% comparing positive and negative scans in patients with lung cancer imaged for IS or FOM. Conclusion: Our analyses demonstrated that NaF PET scan results are highly associated with subsequent hospice claims and, ultimately, with patient survival. NaF PET provides important information on the presence of osseous metastasis and prognosis to assist patients and their physicians when making decisions on whether to select palliative care and transition to hospice or whether to continue treatment.

18F-FDG as an inflammation biomarker for imaging dengue virus infection and treatment response

Development of antiviral therapy against acute viral diseases, such as dengue virus (DENV), suffers from the narrow window of viral load detection in serum during onset and clearance of infection and fever. We explored a biomarker approach using 18F-fluorodeoxyglucose (18F-FDG) PET in established mouse models for primary and antibody-dependent enhancement infection with DENV. 18F-FDG uptake was most prominent in the intestines and correlated with increased virus load and proinflammatory cytokines. Furthermore, a significant temporal trend in 18F-FDG uptake was seen in intestines and selected tissues over the time course of infection. Notably, 18F-FDG uptake and visualization by PET robustly differentiated treatment-naive groups from drug-treated groups as well as nonlethal from lethal infections with a clinical strain of DENV2. Thus, 18F-FDG may serve as a novel DENV infection-associated inflammation biomarker for assessing treatment response during therapeutic intervention trials.

Evaluation of Cross-Calibrated 68Ge/68Ga Phantoms for Assessing PET/CT Measurement Bias in Oncology Imaging for Single- and Multicenter Trials

Quantitative PET imaging is an important tool for clinical trials evaluating the response of cancers to investigational therapies. The standardized uptake value, used as a quantitative imaging biomarker, is dependent on multiple parameters that may contribute bias and variability. The use of long-lived, sealed PET calibration phantoms offers the advantages of known radioactivity activity concentration and simpler use than aqueous phantoms. We evaluated scanner and dose calibrator sources from two batches of commercially available kits, together at a single site and distributed across a local multicenter PET imaging network. We found that radioactivity concentration was uniform within the phantoms. Within the regions of interest drawn in the phantom images, coefficients of variation of voxel values were less than 2%. Across phantoms, coefficients of variation for mean signal were close to 1%. Biases of the standardized uptake value estimated with the kits varied by site and were seen to change in time by approximately ±5%. We conclude that these biases cannot be assumed constant over time. The kits provide a robust method to monitor PET scanner and dose calibrator biases, and resulting biases in standardized uptake values.

Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tübingen, Germany

This paper summarises the proceedings and discussions at the third annual workshop held in Tübingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".

PET/CT, MR, and PET/MR in Lymphoma and Melanoma

With the introduction of hybrid imaging technologies such as PET/CT and recently PET/MRI, staging and therapy-response monitoring have evolved. PET/CT has been shown to be of value for routine staging of FDG-avid lymphomas before as well as at the end of treatment. For interim staging, trials are ongoing to evaluate the use of PET/CT. In melanoma, PET/CT can be recommended for stages III and IV diseases for initial staging and before surgery. Studies investigating the use of PET/CT for early therapy response are promising. The role of PET/MR in lymphoma and melanoma imaging has to be defined because no larger studies exist so far. There may be an application of PET/MR in research especially for tumor characterization and therapy response. Furthermore, the potential role of non-FDG tracers is elucidated regarding the assessment of treatment response in targeted drug regimens.

Use of Positron Emission Tomography to Detect Recurrence and Associations With Survival in Patients With Lung and Esophageal Cancers

BACKGROUND

Positron emission tomography (PET) scans are often used in cancer patients for staging, restaging, and monitoring for treatment response. These scans are also often used to detect recurrence in asymptomatic patients, despite a lack of evidence demonstrating improved survival. We sought to evaluate utilization of PET for this purpose and relationships with survival for patients with lung and esophageal cancers.

METHODS

Using national Surveillance, Epidemiology, and End Results (SEER) and Medicare-linked data, we identified incident patient cases from 2005 to 2009, with follow-up through 2011. We identified cohorts with primary lung (n = 97 152) and esophageal (n = 4446) cancers. Patient and tumor characteristics were used to calculate risk-adjusted two-year overall survival. Using Medicare claims, we examined PET utilization in person-years (to account for variable time in cohorts), excluding scans for staging and for follow-up of CT findings. We then stratified hospitals by quintiles of PET utilization for adjusted two-year survival analysis. All statistical tests were two-sided.

RESULTS

There was statistically significant variation in utilization of PET. Lowest vs highest utilizing hospitals performed .05 (SD = 0.04) vs 0.70 (SD = 0.44) scans per person-year for lung cancer and 0.12 (SD = 0.06) vs 0.97 (SD = 0.29) scans per person-year for esophageal cancer. Despite this, for those undergoing PET, lowest vs highest utilizing hospitals had an adjusted two-year survival of 29.0% (SD = 12.1%) vs 28.8% (SD = 7.2%) for lung cancer (P = .66) and 28.4% (SD = 7.2%) vs 30.3% (SD = 5.9%) for esophageal cancer (P = .55).

CONCLUSIONS

Despite statistically significant variation in use of PET to detect tumor recurrence, there was no association with improved two-year survival. These findings suggest possible overuse of PET for recurrence detection, which current Medicare policy would not appear to substantially affect.

Focal colorectal uptake in (18)FDG-PET/CT: maximum standard uptake value as a trigger in a semi-automated screening setting

BACKGROUND

Focal colorectal uptake in (18)FDG-PET/CT may be associated with a malignancy and can be quantified. This provides the basis for an automatic trigger threshold above which cases are flagged for colonoscopic evaluation and below which for individual assessment.

PURPOSE

To determine the lowest maximum standard uptake (SUVmax) in colorectal cancer that could be used as a threshold to trigger endoscopic evaluation and to evaluate whether the SUVmax needs to be further normalised to a priori known extrinsic factors.

METHODS

The SUVmax was measured in 54 colorectal carcinomas and correlated with gender, age, blood glucose level, injected activity, body mass index and time to scan using t test or correlation coefficients (Pearson or Spearman, according to distribution).

RESULTS

There was no correlation between SUVmax and any of the extrinsic factors mentioned above. The lowest SUVmax value was 5 [mean ± SD (range): 11.1 ± 4.8 (5.0-24.6)].

CONCLUSION

In contrast to most other screening techniques, semi-automation in colorectal screening seems possible with PET/CT. This opens the door for further study into the feasibility of automated screening. Independent from extrinsic factors, an SUVmax ≥5.0 in a focal colorectal uptake in (18)FDG-PET/CT should automatically trigger for endoscopic evaluation, if not contraindicated. Cases with SUVmax <5 should be assessed individually before referral for endoscopy. Thus, more interpretation time could be spent on those cases with a lower uptake and more ambiguous diagnosis.

FDG PET/CT in cancer: comparison of actual use with literature-based recommendations

Purpose

The Region of Southern Denmark (RSD), covering 1.2 of Denmark’s 5.6 million inhabitants, established a task force to (1) retrieve literature evidence for the clinical use of positron emission tomography (PET)/CT and provide consequent recommendations and further to (2) compare the actual use of PET/CT in the RSD with these recommendations. This article summarizes the results.

Methods

A Work Group appointed a professional Subgroup which made Clinician Groups conduct literature reviews on six selected cancers responsible for 5,768 (62.6 %) of 9,213 PET/CT scans in the RSD in 2012. Rapid Evidence Assessment was applied, using the methodology of systematic reviews with predefined limitations to search PubMed, Embase and the Cochrane Library for articles published in English/Danish/Swedish/Norwegian since 2002. PICO questions were defined, data recorded and quality appraised and rated with regard to strength and evidence level. Consequent recommendations for applications of PET/CT were established. The actual use of PET/CT was compared with these, where grades A and B indicated “established” and “useful” and grades C and D “potentially useful” and “non-recommendable” indications, respectively.

Results

Of 11,729 citations, 1,729 were considered for review, and 204 were included. The evidence suggested usefulness of PET/CT in lung, lymphoma, melanoma, head and neck, and colorectal cancers, whereas evidence was sparse in gynaecological cancers. The agreement between actual use of PET/CT and literature-based recommendations was high in the first five mentioned cancers in that 96.2 % of scans were made for grade A or B indications versus only 22.2 % in gynaecological cancers.

Conclusion

Evidence-based usefulness was reported in five of six selected cancers; evidence was sparse in the sixth, gynaecological cancers. Actual use of PET/CT agreed well with recommendations.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-015-3217-0) contains supplementary material, which is available to authorized users.

Appropriateness criteria of FDG PET/CT in oncology

(18)Fluorine-2-fluoro-2-Deoxy-d-glucose ((18)F-FDG) positron emission tomography/computerized tomography (PET/CT) is a well-established functional imaging method widely used in oncology. In this article, we have incorporated the various indications for (18)FDG PET/CT in oncology based on available evidence and current guidelines. Growing body of evidence for use of (18)FDG PET/CT in select tumors is also discussed. This article attempts to give the reader an overview of the appropriateness of using (18)F-FDG PET/CT in various malignancies.

Rifaximin suppresses background intestinal 18F-FDG uptake on PET/CT scans

BACKGROUND

Identification of cancer or inflammatory bowel disease in the intestinal tract by PET/computed tomography (CT) imaging can be hampered by physiological uptake of F-fluorodeoxyglucose (F-FDG) in the normal colon. Previous work has localized this F-FDG uptake to the intestinal lumen, predominantly occupied by bacteria. We sought to determine whether pretreatment with an antibiotic could reduce F-FDG uptake in the healthy colon.

PATIENTS AND METHODS

Thirty patients undergoing restaging PET/CT for nongastrointestinal lymphoma were randomly selected to receive rifaximin 550 mg twice daily for 2 days before their scan (post-rifaximin). Their PET/CT images were compared with those from their prior study (pre-rifaximin). Cecal maximum standard uptake value (SUVmax) and overall colonic F-FDG uptake were compared between scans. All PET/CT images were blindly scored by a radiologist. The same comparison of sequential scans was also undertaken in 30 patients who did not receive antibiotics.

RESULTS

Thirty post-rifaximin scans were compared with 30 pre-rifaximin scans in the same patients. SUVmax in the cecum was significantly lower in the patient's post-rifaximin scans than in their pre-rifaximin scans (P=0.002). The percentage of scans with greater than grade 1 colonic F-FDG uptake was significantly lower in the post-rifaximin scans than in the pre-rifaximin scans (P<0.05). In contrast, there was no significant difference in the paired sequential scans from control patients, nor a reduction in the percentage of scans with greater than grade 1 colonic F-FDG uptake.

CONCLUSION

This pilot study shows that treatment with rifaximin for 2 days before PET/CT scanning can significantly reduce physiological F-FDG uptake in the normal colonic lumen.

FDG PET/CT in infection and inflammation--current and emerging clinical applications

Integrated positron emission tomography/computed tomography (PET/CT) with the glucose analogue, 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), is an evolving hybrid imaging technique in the evaluation of an important and diverse group of pathological conditions, which are characterised by infection and aseptic inflammation. With a rapidly expanding body of evidence, it is being increasingly recognised that, in addition to its established role in oncological imaging, FDG PET/CT also has clinical utility in suspected infection and inflammation. The technique can identify the source of infection or inflammation in a timely fashion ahead of morphological changes on conventional anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), map the extent and severity of disease, identify sites for tissue sampling, and assess therapy response. FDG PET/CT exhibits distinct advantages over traditional radionuclide imaging techniques in terms of shorter duration of examination, higher spatial resolution, non-invasive nature of acquisition, ability to perform quantitative analyses, and the provision of a synergistic combination of functional and anatomical imaging. With the use of illustrative clinico-radiological cases, this article discusses the current and emerging evidence for the use of FDG PET/CT in a broad spectrum of disorders, such as fever of unknown origin, sarcoidosis, large vessel vasculitis, musculoskeletal infections, joint prosthesis or implant-related complications, human immunodeficiency virus (HIV)-related infections, and miscellaneous indications, such as IgG4-related systemic disease. It will also briefly summarise the role of more novel tracers such as FDG-labelled leukocytes and gallium-68 PET tracers in this arena.

Comparison of restaging accuracy of repeat FDG-PET/CT with pelvic MRI after preoperative chemoradiation in patients with rectal cancer

PURPOSE

The aim of this study was to compare the restaging accuracy of repeat fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scan with pelvic magnetic resonance imaging (MRI) in patients with rectal cancer who have undergone preoperative chemoradiation.

METHODS

One hundred and eighty-one consecutive patients with locally advanced rectal cancer who underwent a total mesorectal excision after preoperative chemoradiation were prospectively enrolled. All the patients underwent FDG-PET/CT and pelvic MRI before chemoradiation and 5 weeks after the completion of chemoradiation. We evaluated the measurements of the FDG uptake (SUV(max)) and the percentage of SUV(max) difference (Response Index = RI) between the pre- and postchemoradiation FDG-PET/CT scans. The accuracy of repeat FDG-PET/CT and pelvic MRI for predicting pathologic CR were compared.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of pelvic MRI for predicting pathologic CR were 38.5, 58.1, 13.3, 84.9, and 55.2%, respectively. In terms of FDG-PET/CT, pretreatment tumor size and pathologic stage were significantly correlated with the RI values. Using a RI value of 63.6% as the cutoff threshold, it was possible to discriminate the CR from the non-CR with a sensitivity of 73.1%, a specificity of 64.5%, a PPV of 25.7%, a NPV of 93.5%, and an accuracy of 65.7% (area under the curve = 0.723, 95% confidence interval 0.619-0.828, P < 0.001).

CONCLUSIONS

The accuracy of FDG-PET/CT restaging is superior to that of MRI staging for predicting pathologic CR in irradiated rectal cancer. An NPV of 93.5% indicates that FDG-PET/CT can rule out the pathologic CR.

The clinical use of PET/CT in the evaluation of melanoma

Positron emission tomography combined with computed tomography (PET/CT) has emerged in the last decade as a dominant imaging modality used for staging, monitoring response and surveillance of various cancers, including melanoma. Using 2-deoxy-2-((18)F)fluoro-D-glucose ((18)F-FDG) as the radiopharmaceutical, PET/CT has demonstrated its efficacy and its utility in the management of patients with advanced melanoma. Nonetheless, challenges remain in the early stage evaluation of melanoma and in the development of novel radiotracers to better characterize lesions found on PET/CT. This chapter focuses on the advantages and limitations of this imaging modality in melanoma. We also detail and describe the approach to perform (18)F-FDG PET/CT, the methods to accurately quantify lesions, as well as the pearls/pitfalls of image interpretation. Finally, an overview of preclinical and investigational clinical radiopharmaceuticals is presented.

PET/CT imaging in cancer: current applications and future directions

Positron emission tomography (PET) is a radiotracer imaging method that yields quantitative images of regional in vivo biology and biochemistry. PET, now used in conjunction with computed tomography (CT) in PET/CT devices, has had its greatest impact to date on cancer and is now an important part of oncologic clinical practice and translational cancer research. In this review of current applications and future directions for PET/CT in cancer, the authors first highlight the basic principles of PET followed by a discussion of the biochemistry and current clinical applications of the most commonly used PET imaging agent, (18) F-fluorodeoxyglucose (FDG). Then, emerging methods for PET imaging of other biologic processes relevant to cancer are reviewed, including cellular proliferation, tumor hypoxia, apoptosis, amino acid and cell membrane metabolism, and imaging of tumor receptors and other tumor-specific gene products. The focus of the review is on methods in current clinical practice as well as those that have been translated to patients and are currently in clinical trials.

Impact of (18)F-Fluoride PET on Intended Management of Patients with Cancers Other Than Prostate Cancer: Results from the National Oncologic PET Registry

The National Oncologic PET Registry prospectively assessed the impact of PET with (18)F-sodium fluoride (NaF PET) on intended management of Medicare patients with suspected or known osseous metastasis. We report our findings for cancers other than prostate and make selected comparisons to our previously reported prostate cancer cohort.

METHODS

Data were collected from both referring and interpreting physicians before and after NaF PET in patients (age ≥ 65 y) stratified for initial staging (IS; n = 570), for suspected first osseous metastasis (FOM; n = 1,814; breast, 781 [43%]; lung, 380 [21%]; and all other cancers, 653 [36%]), and for suspected progression of osseous metastasis (POM; n = 435).

RESULTS

The dominant indication was bone pain. If NaF PET were unavailable, conventional bone scintigraphy would have been ordered in 85% of patients. In IS, 28% of patients had suspected or confirmed nonosseous metastasis. If neither conventional bone scintigraphy nor NaF PET were available, referring physicians would have ordered other advanced imaging more than 70% of the time rather than initiate treatment for suspected FOM (11%-16%) or POM (18%-22%). When intended management was classified as either treatment or nontreatment, the intended management change for each cancer type was highest in POM, lower in IS, and lowest in FOM. For suspected FOM, intended management change was lower in breast (24%), lung (36%), or other cancers (31%), compared with prostate cancer (44%) (P < 0.0001), but the NaF PET finding (normal/benign/equivocal, probable, or definite metastases) frequencies were similar across cancer types. After normal/benign/equivocal PET results, 15% of breast, 30% lung, and 38% prostate cancer patients had treatment, likely reflecting differences in management of nonosseous disease. For patients with definite metastasis on NaF PET, nonprostate, compared with prostate, cancer patients had post-PET plans for more frequent biopsy, alternative imaging, chemotherapy, and radiotherapy. In the smaller IS and POM cohorts, differences among cancer types were not significant.

CONCLUSION

Overall, NaF PET led to change in intended management in a substantial fraction of nonprostate cancer patients. In the setting of suspected FOM, NaF PET had a lower immediate impact on the treat/nontreat decision in nonprostate versus prostate cancer patients, which is consistent with current practice guidelines.

Impact of 18F-fluoride PET in patients with known prostate cancer: initial results from the National Oncologic PET Registry

Under Medicare's Coverage with Evidence Development policy, PET using (18)F-sodium fluoride (NaF PET) to identify osseous metastasis became a covered service if prospective registry data were collected. The National Oncologic PET Registry (NOPR) developed a NaF PET registry built on the foundation of its prior registry for PET with (18)F-FDG. Men with prostate cancer represented 72% of the cases.

METHODS

Prospective data before and after NaF PET were collected from referring and interpreting physicians. The analysis set consisted of consenting men age 65 y or older with prostate cancer undergoing NaF PET for initial staging (IS, n = 1,024), suspected first osseous metastasis (FOM, n = 1,997), or suspected progression of osseous metastasis (POM, n = 510).

RESULTS

Referring physicians indicated that if NaF PET were not available, other advanced imaging (body CT, MR imaging, or (18)F-FDG PET) would be their plan in about half of the cases. After NaF PET, the postimaging plan was revised to treatment in 77%, 52%, and 71% for IS, FOM, and POM, respectively. When intended management was classified as either treatment or nontreatment, the overall change in intended management ranged from 44% to 52% and from 12% to 16% if no effect was assumed for those cases with pre-PET plans for other imaging (imaging-adjusted impact). Interpreting physicians recorded definite findings of bone metastasis in 14%, 29%, and 76% for IS, FOM, and POM, respectively. The intended care patterns varied widely across indication and scan abnormality category combinations.

CONCLUSION

NaF PET has high overall impact, principally related to its effect on replacing intended use of other advanced imaging. Its imaging-adjusted impact was similar to that observed with (18)F-FDG PET for restaging or suspected recurrence in other cancer types.

The Medical Imaging & Technology Alliance conference on research endpoints appropriate for Medicare coverage of new PET radiopharmaceuticals

The outcomes of a 2011 Medical Imaging & Technology Alliance (MITA) conference helped shape considerations about what might be the most appropriate pathways for the regulatory and payment considerations of new PET radiopharmaceuticals. As follow-up to that conference, MITA convened a second conference of stakeholders to advise payers on what might be acceptable endpoints for clinical trials to support the coverage of novel PET agents. The conference involved experts on imaging and clinical research, providers of PET services, as well as representatives of interested medical societies, the PET industry, and the regulatory and payer communities. The principal outcome of their deliberations was that it was unrealistic to expect trials of new PET radiopharmaceuticals to directly demonstrate a health benefit. Rather, intermediate outcomes, such as a positive change in patient management, would be more efficient and appropriate.

Intended versus inferred management after PET for cancer restaging: analysis of Medicare claims linked to a coverage with evidence development registry

BACKGROUND

The National Oncologic PET Registry (NOPR) ascertained changes in the intended management of cancer patients using questionnaire data obtained before and after positron emission tomography (PET) under Medicare's coverage with evidence development policy.

OBJECTIVE

To assess the concordance between intended care plans and care received as ascertained through administrative claims data.

RESEARCH DESIGN

Analysis of linked data of NOPR participants from 2006 to 2008 and their corresponding Medicare claims.

SUBJECTS

Consenting patients aged older than 65 years having their first PET for restaging of bladder, kidney, ovarian, pancreas, prostate, small cell lung, or stomach cancer.

MEASURES

: Agreement (positive predictive values and κ) between NOPR post-PET intended management plans for treatment (systemic therapy, radiotherapy, surgery, or combinations), biopsy, or watching as compared to claims-inferred care 30 days after PET.

RESULTS

A total of 8460 patients with linked data were assessed. A total of 43.5% had metastatic disease and 45.3% had treatment planned (predominantly systemic therapy only), 11.1% biopsy and 43.5% watching. Claims-confirmed intended plans (positive predictive value) for single-mode systemic therapy in 62.0%, radiation in 66.0%, surgery in 45.6%, and biopsy in 55.7%. A total of 25.7% of patients with a plan of watching had treatment claims. By cancer type, κ ranged for systemic therapy only from 0.17 to 0.40 and for watching from 0.21 to 0.41. Agreement rates varied by cancer types but were minimally associated with patient age, performance status, comorbidity, or stage.

CONCLUSIONS

Among elderly cancer patients undergoing PET for restaging, there was moderate concordance between their physicians' planned management and claims-inferred actions within a narrow time window. When higher accuracy levels are required in future coverage with evidence development studies, alternative designs will be needed.

Modification of staging and treatment of head and neck cancer by FDG-PET/CT prior to radiotherapy

BACKGROUND AND PURPOSE

Reliable tumor staging is a fundamental pre-requisite for efficient tumor therapy and further prognosis. The aim of this study was to compare head and neck cancer (HNC) staging before and after FDG-PET/CT, evaluating the stage modifications for radiotherapy (RT) planning.

PATIENTS AND METHODS

A total of 102 patients with untreated primary HNC, who underwent conventional staging and staging including FDG-PET/CT before RT, were enrolled in this retrospective study. Blinded pre-FDG-PET/CT and post-FDG-PET/CT staging data were compared. The impact on patient management was tested by comparing the intention before and after FDG-PET/CT.

RESULTS

Significant modifications of T, N, and M stage as well as clinical stage were detected after inclusion of FDG-PET/CT data (p = 0.002, 0.0006, 0.001, 0.03, respectively). Overall, the implementation of FDG-PET/CT led to modification of RT intention decision in 14 patients.

CONCLUSIONS

FDG-PET/CT demonstrates essential influence on tumor staging in HNC patients scheduled for irradiation. Implementation of FDG-PET/CT in imaging protocol improves selection of candidates for curative and palliative RT and allows further optimization of treatment management and therapy intention.

Predictors of initial 18F-fluorodeoxyglucose-positron emission tomography indication among patients with colorectal cancer

OBJECTIVES

To evaluate the determinants of initial F-fluorodeoxyglucose (F-FDG)-PET indication following primary colorectal cancer diagnosis among patients who underwent surgery between January 2000 and December 2007 and who were observed at a single institution for at least 2 years after diagnosis.

METHODS

Of the 530 patients who underwent colorectal cancer resection, 113 patients received at least one F-FDG-PET following diagnosis. Outcome variables included indication and time of the first F-FDG-PET following diagnosis. Potential predictors included disease-level and patient-level characteristics. Univariate and multivariate regression analyses were performed.

RESULTS

Patients diagnosed later in the study period and patients with higher-stage disease were more likely to receive their first F-FDG-PET for initial staging (P<0.001 and P=0.016, respectively). Patients with lower-stage disease were more likely to receive their initial F-FDG-PET for suspected recurrence on conventional imaging. When performed more than 2 years after diagnosis, F-FDG-PET was more likely to be ordered for suspected recurrence either on the basis of conventional imaging or on the basis of patient symptoms/tumor markers (P=0.003 and 0.031, respectively). F-FDG-PET demonstrated disease progression in at least 50% of patients referred for each indication (P=0.037).

CONCLUSION

Higher utilization of F-FDG-PET may be appropriate among patients referred for a number of indications including: initial staging, particularly among those with higher-stage disease; suspected recurrence on conventional imaging among patients with lower-stage disease; and suspected recurrence more than 2 years after diagnosis. Further research is needed to verify these findings.

Diagnostic imaging

Physical techniques have always had a key role in medicine, and the second half of the 20th century in particular saw a revolution in medical diagnostic techniques with the development of key imaging instruments: x-ray imaging and emission tomography (nuclear imaging and PET), MRI, and ultrasound. These techniques use the full width of the electromagnetic spectrum, from gamma rays to radio waves, and sound. In most cases, the development of a medical imaging device was opportunistic; many scientists in physics laboratories were experimenting with simple x-ray images within the first year of the discovery of such rays, the development of the cyclotron and later nuclear reactors created the opportunity for nuclear medicine, and one of the co-inventors of MRI was initially attempting to develop an alternative to x-ray diffraction for the analysis of crystal structures. What all these techniques have in common is the brilliant insight of a few pioneering physical scientists and engineers who had the tenacity to develop their inventions, followed by a series of technical innovations that enabled the full diagnostic potential of these instruments to be realised. In this report, we focus on the key part played by these scientists and engineers and the new imaging instruments and diagnostic procedures that they developed. By bringing the key developments and applications together we hope to show the true legacy of physics and engineering in diagnostic medicine.

Therapeutic implications of an enriched cancer stem-like cell population in a human osteosarcoma cell line

BACKGROUND

Osteosarcoma is a bone-forming tumor of mesenchymal origin that presents a clinical pattern that is consistent with the cancer stem cell model. Cells with stem-like properties (CSCs) have been identified in several tumors and hypothesized as the responsible for the relative resistance to therapy and tumor relapses. In this study, we aimed to identify and characterize CSCs populations in a human osteosarcoma cell line and to explore their role in the responsiveness to conventional therapies.

METHODS

CSCs were isolated from the human MNNG/HOS cell line using the sphere formation assay and characterized in terms of self-renewal, mesenchymal stem cell properties, expression of pluripotency markers and ABC transporters, metabolic activity and tumorigenicity. Cell's sensitivity to conventional chemotherapeutic agents and to irradiation was analyzed and related with cell cycle-induced alterations and apoptosis.

RESULTS

The isolated CSCs were found to possess self-renewal and multipotential differentiation capabilities, express markers of pluripotent embryonic stem cells Oct4 and Nanog and the ABC transporters P-glycoprotein and BCRP, exhibit low metabolic activity and induce tumors in athymic mice. Compared with parental MNNG/HOS cells, CSCs were relatively more resistant to both chemotherapy and irradiation. None of the treatments have induced significant cell-cycle alterations and apoptosis in CSCs.

CONCLUSIONS

MNNG/HOS osteosarcoma cells contain a stem-like cell population relatively resistant to conventional chemotherapeutic agents and irradiation. This resistant phenotype appears to be related with some stem features, namely the high expression of the drug efflux transporters P-glycoprotein and BCRP and their quiescent nature, which may provide a biological basis for resistance to therapy and recurrence commonly observed in osteosarcoma.

Using patient management as a surrogate for patient health outcomes in diagnostic test evaluation

Background

Before a new test is introduced in clinical practice, evidence is needed to demonstrate that its use will lead to improvements in patient health outcomes. Studies reporting test accuracy may not be sufficient, and clinical trials of tests that measure patient health outcomes are rarely feasible. Therefore, the consequences of testing on patient management are often investigated as an intermediate step in the pathway. There is a lack of guidance on the interpretation of this evidence, and patient management studies often neglect a discussion of the limitations of measuring patient management as a surrogate for health outcomes.

Methods

We discuss the rationale for measuring patient management, describe the common study designs and provide guidance about how this evidence should be reported.

Results

Interpretation of patient management studies relies on the condition that patient management is a valid surrogate for downstream patient benefits. This condition presupposes two critical assumptions: the test improves diagnostic accuracy; and the measured changes in patient management improve patient health outcomes. The validity of this evidence depends on the certainty around these critical assumptions and the ability of the study design to minimise bias. Three common designs are test RCTs that measure patient management as a primary endpoint, diagnostic before-after studies that compare planned patient management before and after testing, and accuracy studies that are extended to report on the actual treatment or further tests received following a positive and negative test result.

Conclusions

Patient management can be measured as a surrogate outcome for test evaluation if its limitations are recognised. The potential consequences of a positive and negative test result on patient management should be pre-specified and the potential patient benefits of these management changes clearly stated. Randomised comparisons will provide higher quality evidence about differences in patient management using the new test than observational studies. Regardless of the study design used, the critical assumption that patient management is a valid surrogate for downstream patient benefits or harms must be discussed in these studies.