Solitary pulmonary nodules: impact of quantitative contrast-enhanced CT on the cost-effectiveness of FDG-PET

Dynamic contrast-enhanced CT compared with positron emission tomography CT to characterise solitary pulmonary nodules: the SPUtNIk diagnostic accuracy study and economic modelling

BACKGROUND

Current pathways recommend positron emission tomography-computerised tomography for the characterisation of solitary pulmonary nodules. Dynamic contrast-enhanced computerised tomography may be a more cost-effective approach.

OBJECTIVES

To determine the diagnostic performances of dynamic contrast-enhanced computerised tomography and positron emission tomography-computerised tomography in the NHS for solitary pulmonary nodules. Systematic reviews and a health economic evaluation contributed to the decision-analytic modelling to assess the likely costs and health outcomes resulting from incorporation of dynamic contrast-enhanced computerised tomography into management strategies.

DESIGN

Multicentre comparative accuracy trial.

SETTING

Secondary or tertiary outpatient settings at 16 hospitals in the UK.

PARTICIPANTS

Participants with solitary pulmonary nodules of ≥ 8 mm and of ≤ 30 mm in size with no malignancy in the previous 2 years were included.

INTERVENTIONS

Baseline positron emission tomography-computerised tomography and dynamic contrast-enhanced computer tomography with 2 years' follow-up.

MAIN OUTCOME MEASURES

Primary outcome measures were sensitivity, specificity and diagnostic accuracy for positron emission tomography-computerised tomography and dynamic contrast-enhanced computerised tomography. Incremental cost-effectiveness ratios compared management strategies that used dynamic contrast-enhanced computerised tomography with management strategies that did not use dynamic contrast-enhanced computerised tomography.

RESULTS

A total of 380 patients were recruited (median age 69 years). Of 312 patients with matched dynamic contrast-enhanced computer tomography and positron emission tomography-computerised tomography examinations, 191 (61%) were cancer patients. The sensitivity, specificity and diagnostic accuracy for positron emission tomography-computerised tomography and dynamic contrast-enhanced computer tomography were 72.8% (95% confidence interval 66.1% to 78.6%), 81.8% (95% confidence interval 74.0% to 87.7%), 76.3% (95% confidence interval 71.3% to 80.7%) and 95.3% (95% confidence interval 91.3% to 97.5%), 29.8% (95% confidence interval 22.3% to 38.4%) and 69.9% (95% confidence interval 64.6% to 74.7%), respectively. Exploratory modelling showed that maximum standardised uptake values had the best diagnostic accuracy, with an area under the curve of 0.87, which increased to 0.90 if combined with dynamic contrast-enhanced computerised tomography peak enhancement. The economic analysis showed that, over 24 months, dynamic contrast-enhanced computerised tomography was less costly (£3305, 95% confidence interval £2952 to £3746) than positron emission tomography-computerised tomography (£4013, 95% confidence interval £3673 to £4498) or a strategy combining the two tests (£4058, 95% confidence interval £3702 to £4547). Positron emission tomography-computerised tomography led to more patients with malignant nodules being correctly managed, 0.44 on average (95% confidence interval 0.39 to 0.49), compared with 0.40 (95% confidence interval 0.35 to 0.45); using both tests further increased this (0.47, 95% confidence interval 0.42 to 0.51).

LIMITATIONS

The high prevalence of malignancy in nodules observed in this trial, compared with that observed in nodules identified within screening programmes, limits the generalisation of the current results to nodules identified by screening.

CONCLUSIONS

Findings from this research indicate that positron emission tomography-computerised tomography is more accurate than dynamic contrast-enhanced computerised tomography for the characterisation of solitary pulmonary nodules. A combination of maximum standardised uptake value and peak enhancement had the highest accuracy with a small increase in costs. Findings from this research also indicate that a combined positron emission tomography-dynamic contrast-enhanced computerised tomography approach with a slightly higher willingness to pay to avoid missing small cancers or to avoid a 'watch and wait' policy may be an approach to consider.

FUTURE WORK

Integration of the dynamic contrast-enhanced component into the positron emission tomography-computerised tomography examination and the feasibility of dynamic contrast-enhanced computerised tomography at lung screening for the characterisation of solitary pulmonary nodules should be explored, together with a lower radiation dose protocol.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42018112215 and CRD42019124299, and the trial is registered as ISRCTN30784948 and ClinicalTrials.gov NCT02013063.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 17. See the NIHR Journals Library website for further project information.

Comparative accuracy and cost-effectiveness of dynamic contrast-enhanced CT and positron emission tomography in the characterisation of solitary pulmonary nodules

INTRODUCTION

Dynamic contrast-enhanced CT (DCE-CT) and positron emission tomography/CT (PET/CT) have a high reported accuracy for the diagnosis of malignancy in solitary pulmonary nodules (SPNs). The aim of this study was to compare the accuracy and cost-effectiveness of these.

METHODS

In this prospective multicentre trial, 380 participants with an SPN (8-30 mm) and no recent history of malignancy underwent DCE-CT and PET/CT. All patients underwent either biopsy with histological diagnosis or completed CT follow-up. Primary outcome measures were sensitivity, specificity and overall diagnostic accuracy for PET/CT and DCE-CT. Costs and cost-effectiveness were estimated from a healthcare provider perspective using a decision-model.

RESULTS

312 participants (47% female, 68.1±9.0 years) completed the study, with 61% rate of malignancy at 2 years. The sensitivity, specificity, positive predictive value and negative predictive values for DCE-CT were 95.3% (95% CI 91.3 to 97.5), 29.8% (95% CI 22.3 to 38.4), 68.2% (95% CI 62.4% to 73.5%) and 80.0% (95% CI 66.2 to 89.1), respectively, and for PET/CT were 79.1% (95% CI 72.7 to 84.2), 81.8% (95% CI 74.0 to 87.7), 87.3% (95% CI 81.5 to 91.5) and 71.2% (95% CI 63.2 to 78.1). The area under the receiver operator characteristic curve (AUROC) for DCE-CT and PET/CT was 0.62 (95% CI 0.58 to 0.67) and 0.80 (95% CI 0.76 to 0.85), respectively (p<0.001). Combined results significantly increased diagnostic accuracy over PET/CT alone (AUROC=0.90 (95% CI 0.86 to 0.93), p<0.001). DCE-CT was preferred when the willingness to pay per incremental cost per correctly treated malignancy was below £9000. Above £15 500 a combined approach was preferred.

CONCLUSIONS

PET/CT has a superior diagnostic accuracy to DCE-CT for the diagnosis of SPNs. Combining both techniques improves the diagnostic accuracy over either test alone and could be cost-effective.

TRIAL REGISTRATION NUMBER

NCT02013063.

Dynamic contrast-enhanced computed tomography for the diagnosis of solitary pulmonary nodules: a systematic review and meta-analysis

INTRODUCTION

A systematic review and meta-analysis were performed to determine the diagnostic performance of dynamic contrast-enhanced computed tomography (DCE-CT) for the differentiation between malignant and benign pulmonary nodules.

METHODS

Ovid MEDLINE and EMBASE were searched for studies published up to October 2018 on the diagnostic accuracy of DCE-CT for the characterisation of pulmonary nodules. For the index test, studies with a minimum of a pre- and post-contrast computed tomography scan were evaluated. Studies with a reference standard of biopsy for malignancy, and biopsy or 2-year follow-up for benign disease were included. Study bias was assessed using QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies). The sensitivities, specificities, and diagnostic odds ratios were determined along with 95% confidence intervals (CIs) using a bivariate random effects model.

RESULTS

Twenty-three studies were included, including 2397 study participants with 2514 nodules of which 55.3% were malignant (1389/2514). The pooled accuracy results were sensitivity 94.8% (95% CI 91.5; 96.9), specificity 75.5% (69.4; 80.6), and diagnostic odds ratio 56.6 (24.2-88.9). QUADAS 2 assessment showed intermediate/high risk of bias in a large proportion of the studies (52-78% across the domains). No difference was present in sensitivity or specificity between subgroups when studies were split based on CT technique, sample size, nodule size, or publication date.

CONCLUSION

DCE-CT has a high diagnostic accuracy for the diagnosis of pulmonary nodules although study quality was indeterminate in a large number of cases.

KEY POINTS

• The pooled accuracy results were sensitivity 95.1% and specificity 73.8% although individual studies showed wide ranges of values. • This is comparable to the results of previous meta-analyses of PET/CT (positron emission tomography/computed tomography) diagnostic accuracy for the diagnosis of solitary pulmonary nodules. • Robust direct comparative accuracy and cost-effectiveness studies are warranted to determine the optimal use of DCE-CT and PET/CT in the diagnosis of SPNs.

Cost-effectiveness of second-line diagnostic investigations in patients included in the DANTE trial: a randomized controlled trial of lung cancer screening with low-dose computed tomography

AIM

The aim of this study was to analyze the economic efficiency of second-line diagnostic investigations in patients with undetermined lung nodules.

PARTICIPANTS AND METHODS

A retrospective review of all surgical cases included in the DANTE trial from 2001 to 2006 for lung cancer screening was performed. Overall, 217 patients and 261 lung nodules were analyzed. The cohort was divided into patients investigated with PET and/or computed tomography (CT)-guided biopsy (PET-CTB protocol; N=100), compared with those assessed with serial low-dose CT scans (standard protocol; N=161). Outpatient's and inpatient's costs were expressed in euros and derived from the Italian National Health Service. Ineffective costs were defined as the cost of procedures that lead to avoidable surgical intervention.

RESULTS

The diagnostic accuracy of the two protocols was 91% for the standard (sensitivity 100%, specificity 91%, positive predictive value 26%, and negative predictive value 100%) and 90% for the PET-CTB protocol (sensitivity 98%, specificity 81%, positive predictive value 85%, and negative predictive value 97%). Average costs for outpatient's diagnostics were 694 and 1.462 euros, respectively, for the standard and PET-CTB protocol. Average inpatient's costs for both protocols were 12.121 euros. The two protocols showed comparable effectiveness in terms of outpatient's costs (94 and 90%, respectively; P=0.252). Inpatient's costs were effective in 36% of cases monitored according to the standard protocol compared with 85% of patients investigated with PET-CTB protocol. Ineffective costs corresponded to 64 and 15%, respectively (P<0.0001).

CONCLUSION

Despite a higher average cost for outpatient's diagnostics, the implementation of PET imaging with or without CT-guided needle biopsy in the workup of suspicious lung nodules results in reduced unnecessary harm and costs related to inpatient's procedures.

Accuracy and cost-effectiveness of dynamic contrast-enhanced CT in the characterisation of solitary pulmonary nodules-the SPUtNIk study

INTRODUCTION

Solitary pulmonary nodules (SPNs) are common on CT. The most cost-effective investigation algorithm is still to be determined. Dynamic contrast-enhanced CT (DCE-CT) is an established diagnostic test not widely available in the UK currently.

METHODS AND ANALYSIS

The SPUtNIk study will assess the diagnostic accuracy, clinical utility and cost-effectiveness of DCE-CT, alongside the current CT and 18-flurodeoxyglucose-positron emission tomography) (18FDG-PET)-CT nodule characterisation strategies in the National Health Service (NHS). Image acquisition and data analysis for 18FDG-PET-CT and DCE-CT will follow a standardised protocol with central review of 10% to ensure quality assurance. Decision analytic modelling will assess the likely costs and health outcomes resulting from incorporation of DCE-CT into management strategies for patients with SPNs.

ETHICS AND DISSEMINATION

Approval has been granted by the South West Research Ethics Committee. Ethics reference number 12/SW/0206. The results of the trial will be presented at national and international meetings and published in an Health Technology Assessment (HTA) Monograph and in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN30784948; Pre-results.

Solitary pulmonary nodule and (18)F-FDG PET/CT. Part 2: accuracy, cost-effectiveness, and current recommendations

A solitary pulmonary nodule is a common, often incidental, radiographic finding. The investigation and differential diagnosis of solitary pulmonary nodules remain complex, because there are overlaps between the characteristics of benign and malignant processes. There are currently many strategies for evaluating solitary pulmonary nodules. The main objective is to identify benign lesions, in order to avoid exposing patients to the risks of invasive methods, and to detect cases of lung cancer accurately, in order to avoid delaying potentially curative treatment. The focus of this study was to review the evaluation of solitary pulmonary nodules, to discuss the current role of (18)F-fluorodeoxyglucose positron-emission tomography, addressing its accuracy and cost-effectiveness, and to detail the current recommendations for the examination in this scenario.

Diagnostic accuracy of contrast-enhanced computed tomography and positron emission tomography with 18-FDG in identifying malignant solitary pulmonary nodules

Contrast-enhanced computed tomography (CECT) and positron emission tomography with 18-FDG (FDG-PET/CT) are used to identify malignant solitary pulmonary nodules. The aim of the study was to evaluate the accuracy of CECT and FDG-PET/CT in diagnosing the etiology of solitary pulmonary nodule (SPN). Eighty patients with newly diagnosed SPN >8 mm were enrolled. The patients were scheduled for either or both, CECT and FDG-PET/CT. The nature of SPN (malignant or benign) was determined either by its pathological examination or radiological criteria. In 71 patients, the etiology of SPN was established and these patients were included in the final analysis. The median SPN diameter in these patients was 13 mm (range 8-30 mm). Twenty-two nodules (31%) were malignant, whereas 49 nodules were benign. FDG-PET/CT was performed in 40 patients, and CECT in 39 subjects. Diagnostic accuracy of CECT was 0.58 (95% confidence interval [CI] 0.41-0.74). The optimal cutoff level discriminating between malignant and benign SPN was an enhancement value of 19 Hounsfield units, for which the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CECT were 100%, 37%, 32%, and 100%, respectively. Diagnostic accuracy of FDG-PET/CT reached 0.9 (95% CI 0.76-0.9). The optimal cutoff level for FDG-PET/CT was maximal standardized uptake value (SUV max) 2.1. At this point, the sensitivity, specificity, PPV, and NPV were 77%, 92%, 83%, and 89%, respectively. The diagnostic accuracy of FDG-PET/CT is higher than that of CECT. The advantage of CECT is its high sensitivity and negative predictive value.

Cost-effectiveness of PET and PET/computed tomography: a systematic review

The development of clinical diagnostic procedures comprises early-phase and late-phase studies to elucidate diagnostic accuracy and patient outcome. Economic assessments of new diagnostic procedures compared with established work-ups indicate additional cost for 1 additional unit of effectiveness measure by means of incremental cost-effectiveness ratios when considering the replacement of the standard regimen by a new diagnostic procedure. This article discusses economic assessments of PET and PET/computed tomography reported until mid-July 2014. Forty-seven studies on cancer and noncancer indications were identified but, because of the widely varying scope of the analyses, a substantial amount of work remains to be done.

Molecular imaging with dynamic contrast-enhanced computed tomography

Dynamic contrast-enhanced computed tomography (DCE-CT) is a quantitative technique that employs rapid sequences of CT images after bolus administration of intravenous contrast material to measure a range of physiological processes related to the microvasculature of tissues. By combining knowledge of the molecular processes underlying changes in vascular physiology with an understanding of the relationship between vascular physiology and CT contrast enhancement, DCE-CT can be redefined as a molecular imaging technique. Some DCE-CT derived parameters reflect tissue hypoxia and can, therefore, provide information about the cellular microenvironment. DCE-CT can also depict physiological processes, such as vasodilatation, that represent the physiological consequences of molecular responses to tissue hypoxia. To date the main applications have been in stroke and oncology. Unlike some other molecular imaging approaches, DCE-CT benefits from wide availability and ease of application along with the use of contrast materials and software packages that have achieved full regulatory approval. Hence, DCE-CT represents a molecular imaging technique that is applicable in clinical practice today.

Positron emission tomography/computed tomography introduction in the clinical management of patients with suspected recurrence of ovarian cancer: a cost-effectiveness analysis

Aim of this study was to evaluate the economic impact of the introduction of positron emission tomography/computed tomography (PET/CT) in the early detection of recurrent ovarian cancer through a cost-effectiveness analysis of different diagnostic strategies. Thirty-two consecutive patients with suspected ovarian cancer recurrence, studied by both contrast enhanced abdominal CT and PET/CT, were retrospectively included in the study. Three different diagnostic strategies were evaluated and compared: (1) CT only or baseline strategy; (2) PET/CT for negative CT or strategy A; (3) PET/CT for All or strategy B. For each one, expected costs, avoided surgery and incremental cost-effectiveness ratio (ICER) were calculated to identify the most cost-effective strategy. The number of positive patients increased from baseline strategy (20/32) to strategy A and B (30/32 and 29/32 respectively). Positron emission tomography/computed tomography reoriented physician choice in 31% and 62% of patients (strategies A and B respectively). Strategy A is dominated by strategy B, which is more expensive (2909 euro vs. 2958 euro), but also more effective (3 cases of surgery avoided) and presents an ICER of 226.77 euro per surgery avoided (range: 49.50-433.00 euro). Positron emission tomography/computed tomography introduction in this population is cost-effective and allowed to redirect the clinical management of patients towards more appropriate therapeutic choices.

Cost and outcomes of patients with solitary pulmonary nodules managed with PET scans

BACKGROUND

No prior study to our knowledge has observed the cost of managing solitary pulmonary nodules of patient groups defined by PET scan results.

METHODS

We combined study and administrative data over 2 years of follow-up.

RESULTS

Of 375 individuals with a definitive diagnosis, 54.4% had a malignant nodule and 62.1% had positive PET scan results. Mortality risk was 5.0 times higher (CI, 3.1-8.2) and cost was greater (50,233 dollars vs 22,461 dollars, P<.0001) among patients with malignant nodule. Mortality risk was 4.1 times higher (CI, 2.4-7.0) and cost was greater (47,823 dollars vs 20,744 dollars, P<.0001) among patients with a positive PET scan result. Among patients with a malignant nodule, 4.9% had a false-negative PET scan, but cost and survival were not different from true positives. Among patients with a benign nodule, 22.8% had a false-positive PET scan. These patients had greater cost (33,783 dollars vs 19,115 dollars, P<.01), more surgeries and biopsies, and 3.8 times the mortality risk (CI, 1.6-9.2) of true negatives. Just over one-half (54.5%) of individuals with positive PET scans received surgery. Most individuals with negative PET scans (85.2%) were managed by watchful waiting. They incurred fewer costs than patients with negative PET scans who were managed more aggressively (19,378 dollars vs 28,611 dollars, P<.01).

CONCLUSIONS

Management of solitary pulmonary nodules is expensive, especially if the nodule is malignant or if the PET scan result is false positive. Among patients with malignant nodules, 2-year survival is poor. Compared with true-positive PET scan results, false-negative results are not associated with lower costs or better outcomes.

PET-CT in oncology: making the most of CT

Combined positron emission tomography–computed tomography (PET-CT) has made a significant impact on cancer imaging. The use of CT to map tissue attenuation for correction of PET images and the ability to co-register the functional information provided by PET with the anatomical data afforded by CT, has resulted in demonstrable improvements in diagnostic accuracy. However, attenuation correction and anatomical localisation may not represent the full benefits of integrating CT with PET. The use of CT acquisition techniques for patient positioning and the use of contrast media can improve diagnostic performance, and incorporation of CT image processing techniques such as perfusion CT, 3D imaging and computer-assisted diagnosis offers new applications. The interpretation of PET-CT images can be improved by fully integrating the morphological appearances on CT into image analysis. Better utilisation of the CT component of PET-CT could further enhance the benefits of PET-CT in oncology but will have implications for manufacturers and purchasers of PET-CT equipment and analysis software. Furthermore, specialists working in PET-CT will need CT competencies beyond knowledge of cross-sectional anatomy. CT continues to exhibit rapid evolution and these advances will inevitably impact on the practice of PET-CT.

Characterization of the solitary pulmonary nodule: 18F-FDG PET versus nodule-enhancement CT

OBJECTIVE

The purpose of this study was to directly compare nodule-enhancement CT and 18F-FDG PET in the characterization of indeterminate solitary pulmonary nodules (SPNs) greater than 7 mm in size.

MATERIALS AND METHODS

Examinations from patients undergoing both nodule-enhancement CT and 18F-FDG PET to characterize the same indeterminate SPN were reviewed. For nodule-enhancement CT, an SPN was considered malignant when it showed an unenhanced to peak contrast-enhanced increase in attenuation greater than 15 H. Fluorine-18-FDG PET studies were blindly reinterpreted by two qualified nuclear radiologists. SPNs qualitatively showing hypermetabolic activity greater than the mediastinal blood pool were interpreted as malignant. These interpretations were compared with the original prospective clinical readings and to semiquantitative standardized uptake value (SUV) analysis. Results were compared with pathologic and clinical follow-up.

RESULTS

Forty-two pulmonary nodules were examined. Twenty-five (60%) were malignant, and 17 (40%) were benign. Nodule-enhancement CT was positive in all 25 malignant nodules and in 12 benign nodules, with sensitivity and specificity of 100% and 29%, respectively, and with a positive predictive value (PPV) and negative predictive value (NPV) of 68% and 100%, respectively. Qualitative 18F-FDG PET interpretations were positive in 24 of the 25 malignant nodules and in four benign nodules. Fluorine-18-FDG PET was considered negative in one malignant nodule and in 13 of the 17 benign nodules. This correlates with a sensitivity and specificity of 96% and 76%, respectively, and with a PPV and NPV of 86% and 93%, respectively. Original prospective 18F-FDG PET and semiquantitative SUV analysis showed sensitivity, specificity, PPV, and NPV of 88%, 76%, 85%, and 81% and 84%, 82%, 88%, and 78%, respectively.

CONCLUSION

Due to its much higher specificity and only slightly reduced sensitivity, 18F-FDG PET is preferable to nodule-enhancement CT in evaluating indeterminate pulmonary nodules. However, nodule-enhancement CT remains useful due to its high NPV, convenience, and lower cost. Qualitative 18F-FDG PET interpretation provided the best balance of sensitivity and specificity when compared with original prospective interpretation or SUV analysis.

Blood flow–metabolic relationships are dependent on tumour size in non-small cell lung cancer: a study using quantitative contrast-enhanced computer tomography and positron emission tomography

PURPOSE

The purpose of this study was to undertake dual assessment of tumour blood flow and glucose metabolism in non-small cell lung cancer (NSCLC) using contrast-enhanced computed tomography (CE-CT) and (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in order to assess how the relationships between these parameters vary with tumour size and stage.

METHODS

Tumour blood flow and glucose metabolism were assessed in 18 NSCLCs using quantitative CE-CT and FDG-PET respectively. Contrast enhancement and FDG uptake were both normalised to injected dose and patient weight to yield correspondingly the standardised perfusion value (SPV) and standardised uptake value (SUV). Tumour area was measured from conventional CT images.

RESULTS

The ratio of SUV to SVP and the metabolic-flow difference (SUV-SVP) correlated with tumour size (r=0.56, p=0.015 and r=0.60 and p=0.008 respectively). A metabolic-flow difference of greater than 4 was more common amongst tumours of stages III and IV (odds ratio 10.5; 95% confidence limits 0.24-32.1). A significant correlation between SUV and SPV was found only for tumours smaller than 4.5 cm2 (r=0.85, p=0.03).

CONCLUSION

Blood flow-metabolic relationships are not consistent in NSCLC but depend upon tumour size and stage. Quantitative CE-CT as an adjunct to an FDG study undertaken using integrated PET-CT offers an efficient way to augment the assessment of tumour biology with possible future application as part of clinical care.

Radiologic evaluation of the solitary pulmonary nodule

The solitary pulmonary nodule (SPN) is a common radiologic finding. There are different management approaches and the work-up often requires evaluation over a long period of time to establish a benign or malignant diagnosis. Comparison with old examinations and morphologic evaluation of the size, margins, and internal characteristics of an (SPN) should be the first step in the evaluation of these lesions. It is often necessary to proceed to additional imaging techniques and in some situations invasive tests or surgical biopsy may be required.

Perfusion CT for the assessment of tumour vascularity: which protocol?

Perfusion CT is a technique that can be readily incorporated into the existing CT protocols that continue to provide the mainstay for anatomical imaging in oncology to provide an in vivo marker of tumour angiogenesis. By capturing physiological information reflecting the tumour vasculature, perfusion CT can be useful for diagnosis, risk-stratification and therapeutic monitoring. However, a wide range of perfusion CT techniques have evolved and the various commercial implementations advocate different acquisition protocols and processing methods. Acquisition choices include first pass studies or delayed imaging, temporal resolution versus image noise, and single location sequences or multiple spiral acquisitions. Data processing may be semi-quantitative or, using either compartmental analysis or deconvolution, produce results that are quantified in absolute physiological terms such as perfusion, blood volume and permeability. This article discusses the advantages and disadvantages of the more common CT perfusion protocols and offers proposals that could allow for easier comparison between studies employing different techniques.

Functional CT imaging in oncology

The two-compartment pharmacokinetics exhibited by iodinated contrast media makes these agents well suited to the study of tumour angiogenesis in which new vessels are not only produced in greater number but also are abnormally permeable to circulating molecules. The temporal changes in contrast enhancement of tumours on CT have been shown to correlate with histopathological assessments of angiogenesis with the intravascular and extravascular phases of contrast enhancement reflecting microvessel density and vascular permeability, respectively. By quantifying tumour contrast enhancement to capture physiological information about the vascular system, functional CT can provide a useful adjunct to the anatomical information afforded by MDCT in oncology, aiding with tumour diagnosis, risk stratification and therapy monitoring. By simultaneously assessing tumour vascularity and metabolic demand, the broader expansion of integrated MDCT/PET imaging will support highly sophisticated assessments of tumour biology within a single examination.

Cancer imaging: is it cost-effective?

With expenditure on imaging patients with cancer set to increase in line with rising cancer prevalence, there is a need to demonstrate the cost-effectiveness of advanced cancer imaging techniques. Cost-effectiveness studies aim to quantify the cost of providing a service relative to the amount of desirable outcome gained, such as improvements in patient survival. Yet, the impact of imaging on the survival of patients with cancer is small compared to the impact of treatment and is therefore hard to measure directly. Hence, techniques such as decision-tree analysis, that model the impact of imaging on survival, are increasingly used for cost-effectiveness evaluations. Using such techniques, imaging strategies that utilise computed tomography, magnetic resonance imaging and positron emission tomography have been shown to be more cost-effective than non-imaging approaches for the management of certain cancers including lung, prostate and lymphoma. There is stronger evidence to support the cost-effectiveness of advanced cancer imaging for diagnosis, staging and monitoring therapy than for screening. The results of cost-effectiveness evaluations are not directly transferable between countries or tumour types and hence more studies are needed. As many of the techniques developed to assess the evidence base for therapeutic modalities are not readily applicable to diagnostic tests, cancer imaging specialists need to define the methods for health technology assessment that are most appropriate to their speciality.

Screening for lung cancer

PURPOSE OF REVIEW

With the development of newer forms of technology such as low-dose spiral computed tomography, there has been a resurgent interest in screening for lung cancer. The purpose of this review is to highlight recent advances in screening for lung cancer. Articles published since September 2002 are reviewed here.

RECENT FINDINGS

More frequent screenings (every 4 or 6 months) showed increased mortality from lung cancer, compared with annual screening. A mass screening conducted in 1990 was effective in a case-control study. The results of lung cancer screening by low-dose spiral computed tomography were reported from the Milan group and the Mayo Clinic. Computed tomography depicted peripheral early lung cancer, especially adenocarcinoma. These results are consistent with previous reports from other groups. Screening with imaging becomes more sensitive with automated computerized methods.

SUMMARY

A high percentage of stage IA lung cancers were detected by screening with low-dose helical computed tomography. The characteristics of the nodules detected by low-dose spiral computed tomography have been clarified. There have been many controversial discussions about cost effectiveness and overdiagnosis. There is still no evidence that screening tests reduce the rate of cancer-specific mortality. Several studies of screening for lung cancer are under way.

Functional computed tomography in oncology

Functional Computed Tomography (CT) describes the use of existing technologies and conventional contrast agents to capture physiological parameters that reflect the vasculature within tumours and other tissues. The technique is readily incorporated into routine conventional CT examinations and, in tumours, the physiological parameters obtained provide an in-vivo marker of angiogenesis. As well as providing a research tool, functional CT has clinical applications in tumour diagnosis, staging, risk stratification and therapy monitoring, including the characterisation of pulmonary nodules, detection of occult hepatic metastases, grading of cerebral glioma and monitoring of anti-angiogenesis drugs. With the recent commercial availability of appropriate software and the development of multislice CT systems, functional CT is poised to make a significant impact upon the imaging of patients with cancer.